Telencephalon Flashcards
Number of Brodman areas
47
6 layers of cerebral cortex
Molecular
External granular
External pyramidal
Internal granular
Internal pyramidal
Multiform
Agranular cortex
Frontal lobe
Dominated by pyramidal rather than granular layers
Granular cortex
Parietal sensory cortex
Functions of non dominant hemisphere
Visual and spatial perception
Visual (non-language dependent) memory
Functions of dominant hemisphere
Language
Language dependent hemisphere
Wada test
Can be used to demonstrate hemispheric dominance.
Injection of sodium amytal into the ICA.
On the dominant side this will cause an arrest of speech for up to 30 seconds.
May be useful prior to temporal lobectomy when there is doubt over hemispheric dominance
Key gyri on the lateral surface of the frontal lobe
Superior frontal gyrus
Middle frontal gyrus
Inferior frontal gyrus (pars triangularis, pars orbitalis, pars opercularis)
Precentral gyrus
Key sulci on lateral surface of frontal lobe
Superior frontal sulcus
Inferior frontal sulcus
Pre-central sulcus
Key gyri on superior view of frontal cortex
Superior frontal gyrus
Middle frontal gyrus
Inferior frontal gyrus
Precentral gyrus
Key sulci on superior view of frontal lobe
Superior frontal sulcus
Inferior frontal sulcus
Precentral sulcus
Key gyri on medial view of frontal lobe
Superior frontal gyrus
Paracentral lobule
Cingulate gyrus
Key sulci on medial surface of frontal lobe
Cingulate sulcus
Key gyri on orbital view of frontal lobe
Gyrus rectus
Medial orbital gyrus
Anterior orbital gyrus
Posterior orbital gyrus
Lateral orbital gyrus
Key sulci on orbital surface of frontal lobe
Olfactory sulcus
Orbital sulcus
Function of precentral gyrus
Motor cortex.
Contralateral movement of face, arm, leg, trunk
Lesion to this area would result in?
This is the precentral gyrus
Monoplegia or hemiplegia depending on extent of damage
Function of Broca’s area (dominant hemisphere)
Expressive centre for speech
Lesions to this area would result in?
Dominant hemisphere:
Broca’s dysphasia (motor or expressive)
Function of SMA
Motor planning
Consequences of lesions affecting this area
SMA
Paralysis of head and eye movements to the opposite side.
Head turns and looks towards the diseased hemisphere and eyes look in the same direction
Hypokinetic mutism
What makes up the prefrontal areas?
Vast parts of the frontal lobes anterior to the motor cortex as well as orbital part of frontal lobes
Causes of prefrontal damage?
Often bilateral e.g. infarction, following haemorrhage from ACommA, neoplasm, trauma or frontal dementia resulting in a change of personality with antisocial behaviour/loss of inhibitions
What are the three prefrontal syndromes?
Orbitofrontal syndrome
Frontal convexity syndrome
Medial frontal syndrome
Feeatures of orbitofrontal syndrome
Disinhibition
Poor judgement
Emotional lability
Features of frontal convexity syndrome
Apathy
Poor abstract thought
Features of medial frontal syndrome
Akinetic
Incontinent
Sparse verbal output
Additional associations of prefrontal lesions
Primitive reflexes e.g. grasp, pout
Disturbance of gait
Resistance to passive movement of limbs- paratonia
Function of paracentral lobule
Cortical inhibition of bladder and bowel voiding
The consequence of a lesion to this area
Loss of cortical inhibition of
Incontinence of urine and faeces
Particularly likely with hydrocephalus and is an important symptom in NPH
If involving motor/sensory leg may also have monoparesis and sensory disturbance in the contralateral lower limb.
Key structures of parietal lobe
Post central gyrus
Superior parietal lobule
Inferior parietal lobule (angular gyrus and supramarginal gyrus)
Key sulci of parietal lobe
Post-central sulcus
Intraparietal suclus
Parieto-occpital sulcus
Function of post-central gyrus
Sensory cortex receives afferent pathways for appreciation of posture touch and passive movement
Function of supramarginal and angular gyri (dominant hemisphere)?
Constitue Wernicke’s language area
This is the receptive area where auditory and visual aspects of comprehension are integrated
Function of non-dominant parietal lobe
Important in concept of body image and awareness of external environment
The ability to construct shapes etc. results from such visual or proprioceptive skills
Optic radiation and parietal lobe
Fibres of lower visual field pass through the parietal lobe
Function of dominant parietal lobe
Implicated in the skills of handling numbers/caclulation
Consequence of lesions to postcentral gyrus
Will result in cortical disturbance of sensation:
Postural
Passive movement
Accurate localisation of light touch
Two-point discrimination
Astereogenesis
Perceptual rivalry (sensory inattention)
Astereognosis
Difficulty appreciating tactile size, shape, texture and weight of objects
Consequence of lesions to supramarginal and angular gyri
Wernicke’s dysphasia
Pathology in which lobes is commonly associated with seizures?
Frontal and temporal
Name structures on the left side of the image
What are the five segments of the internal capsule?
Anterior limb
Genu
Posterior limb
Sublenticular segment
Retrolenticular segment
Components of the anterior limb of the internal capsule
Frontopontine
Thalamocortical
Corticothalamic
Caudatoputamenal
Components of the genu of the internal capsule
Corticobulbar fibres
Corticoreticulobulbar fibres
Components of the posterior limb of the internal capsule
Corticospinal
Corticorubral
Corticothalamic
Thalamocortical
Components of the sublenticular segment of the internal capsule
Auditory radiations
Optic radiations
Corticopontine fibres
Components of the retrolenticular portion of the internal capsule
Optic radiations
Corticotectal fibres
Corticonigral fibres
Corticotegmental fibres
Consequence of dominant hemispheric parietal lesion?
Confusion of right and left limbs,
Difficulty in distinguishing fingers on hand (finger agnosia)
Disturbance of calculation (acalculia)
Disturbance of writing (agraphia)
Constitutes Gerstmann’s syndrome
Gerstmann’s syndrome
Finger agnosia
Agraphia
Acalculia
Left-right disorientation
Gerstmann’s syndrome, which part of the brain
Dominant parietal lobe
Consequence of damage to parietal optic radiation?
Inferior homonymous quadrantopia
Key gyri on the lateral view of temporal lobe?
Superior
Middle
Inferior temporal gyrus
Key gyri on inferior view of temporal lobe?
Inferior temporal gyrus
Fusiform (temporo-occipital gyrus)
Parahippocampal gyrus
Lingual
Uncus
The function of temporal lobe
Auditory cortex:
Dominant hemisphere- hearing of language
Non-dominant hemisphere- hearing of sounds/music
Middle and inferior temporal gyri are involved in learning and memory
Limbic lobe: inferior and medial portions of the temporal lobe including the hippocampus and parahippocampal gyrus
Visual pathways pass deep in the temporal lobe around the posterior horn of the lateral ventricle
Location of the auditory cortex
Lies on the upper surface of the superior temporal gyrus, buried in the lateral sulcus (Heschl’s gyrus)
Brodmann 41, 42
Where do the olfactory nerve fibres terminate?
Uncus
Impairment of temporal lobe function:
Auditory cortex
Cortical deafness- rare as requires bilateral lesions but the patient may develop complete deafness and be unaware
Lesions which involve the surrounding association areas may result in difficulty in hearing spoken words or appreciating rhythm or music (Amusia)
Auditory hallucinations may occur in temporal lobe disease
Impairment of temporal lobe function
Middle and inferior temporal gyrus
Disturbance of memory and learning
Complex partial seizures
Impairment of temporal lobe function:
Limbic lobe
Complex partial seizures
Aggressive or antisocial behaviours
Inability to establish new memories
Damage to temporal part of optic radiation
Upper homonymous quadranatopia
Dominant hemisphere temporal lobe lesion
Speech disturbance
Wernicke’s dysphasia
Location of the visual cortex?
Lies along the banks of the calcarine sulcus, this area is referred to as the striate cortex
Above and below this lies the parastriate cortex
Brodman area 17
Striate cortex=
Parastriate cortex function
Primary visual cortex
When stimulated relays information to the parastriate cortex which is the association visual cortex.
Consequence of cortical lesion affecting occipital lobe
Homonymous hemianopia with or without the involvement of the macula depending on the posterior extent of the lesion.
When only the occipital pole is affected, a central hemianopia field defect involving the macula occurs with a normal peripheral field of vision.
Cortical blindness
Extensive bilateral cortical lesions of the straite cortex will result in cortical blindness.
In this, the pupillary light reflex is normal despite the conscious perception of the presence of illumination
Anton’s syndrome
Cortical lesion affecting both striate and parastriate regions affects the interpretation of vision.
The patient is unaware of his visual loss and denies its presence. This denial in the presence of obvious blindness is Anton’s syndrome
Causes of cortical blindness
May occur in vascular disease (PCA infarct) but also follows hypoxia and hypertensive encephalopathy or after surviving tentorial herniation
Balint’s syndrome
Triad:
Simultagnosia- can see trees but not forest can test with Ishihara colour plates- will see colour but not the number
Optic ataxia- mislocalisation in space, hold a pen out they will miss but they can touch their own finger
Oculomotor apraxia- difficulty with visual pursuit, difficulty initiating
The inability to direct voluntary gaze associated with visual agnosia (loss of visual recognition) due to bilateral parieto-occipital lesions.
https://www.youtube.com/watch?v=A8BD5liH7ug
Posterior ramus of lateral sulcus
Post-central sulcus
Ascending ramus of lateral cerebral sulcus
Pars triangularis
Parieto-occipital sulcus
Cause of prosopagnosia
Patient unable to identify familiar face
Usually causd by bilateral lesions at occipito-temporal junction
Name structures 1-10
- Longitudinal fissure of cerebrum.
- Superior margin of cerebrum.
- Frontal pole.
- Superior frontal sulcus.
- Inferior frontal sulcus.
- Precentral sulcus.
- Central sulcus.
- Postcentral sulcus.
- Intraparietal sulcus.
- Parieto-occipital sulcus.
Name structures 11-20
- Transverse occipital sulcus.
- Occipital pole.
- Superior parietal lobule.
- Inferior parietal lobule.
- Postcentral gyrus.
- Paracentral lobule.
- Precentral gyrus.
- Inferior frontal gyrus.
- Middle frontal gyrus.
- Superior frontal gyrus
Name structures 1-10
- Central sulcus.
- Precentral gyrus.
- Precentral sulcus.
- Superior frontal gyrus.
- Superior frontal sulcus.
- Middle frontal gyrus.
- Middle frontal sulcus.
- Frontal pole.
- Orbital gyri.
- Olfactory bulb.
Name structures 11-20
- Olfactory tract.
12–14. Lateral sulcus.
- Anterior ramus.
- Ascending ramus.
- Posterior ramus.
- Frontal operculum.
- Frontoparietal operculum.
- Superior temporal gyrus.
- Middle temporal gyrus.
- Superior temporal sulcus.
- Inferior temporal sulcus.
Name structures 21-30
- Inferior temporal gyrus.
- Preoccipital notch.
- Occipital pole
- Transverse occipital sulcus.
- Inferior parietal lobule.
- Intraparietal sulcus.
- Superior parietal lobule.
- Postcentral sulcus.
- Postcentral gyrus.
- Supramarginal gyrus.
Name structures 31-36
- Angular gyrus.
- Pons.
- Pyramid (medulla oblongata).
- Olive.
- Flocculus.
- Cerebellar hemisphere.
Name structures 1-10
- Longitudinal fissure of cerebrum,
- Cingulate sulcus.
- Cingulate gyrus.
- Sulcus of corpus callosum.
- Corpus callosum.
- Lateral sulcus.
- Claustrum.
8–9. Corpus striatum.
- Caudate nucleus.
- Putamen.
9–10. Lentiform nucleus.
- Globus pallidus.
Name structures 11-19
- Thalamus.
- Subthalamic nucleus.
- Mamillary body.
- Amygdala.
- Optic tract.
- Third ventricle and choroid plexus.
- Body of fornix.
- Lateral ventricle and choroid plexus.
- Cortex of insula.
Name structures 1-10
- Frontal pole of frontal lobe.
- Medial frontal gyrus.
- Cingulate sulcus.
- Sulcus of corpus callosum.
- Cingulate gyrus.
- Paracentral lobule.
- Precuneus.
- Subparietal sulcus.
- Parieto-occipital sulcus.
- Cuneus.
Name structures 11-20
- Calcarine fissure.
- Occipital pole of occipital lobe.
13–16. Corpus callosum (cut surface).
- Rostrum.
- Genu.
- Body.
- Splenium.
- Lamina terminalis (cut surface).
- Anterior commissure (cut surface).
- Septum pellucidum.
- Fornix.
Name structures 21-30
- Tela choroidea of third ventricle.
- Choroid plexus of third ventricle (cut edge).
- Transverse cerebral fissure.
- Thalamus.
- Interthalamic adhesion (cut surface).
- Interventricular foramen of Monro.
- Hypothalamus.
- Suprapineal recess and pineal body (cut surface).
- Vermis of cerebellum (cut surface).
- Cerebellar hemisphere.
Name structures 31-40
- Choroid plexus of fourth ventricle.
- Medulla oblongata (cut surface).
- Fourth ventricle.
- Pons (cut surface).
- Tectal lamina (cut surface) and mesencephalic aqueduct of Sylvius.
- Mamillary body.
- Oculomotor nerve.
- Infundibular recess.
- Temporal lobe lateral occipitotemporal gyrus (fusiform gyrus)
- Rhinal fissure.
Name structures 41-44
- Hypophysis (cut surface) with adenohypophysis (anterior lobe) and neurohypophysis (posterior lobe) of the pituitary gland.
- Optic chiasm (cut surface).
- Optic nerve.
- Olfactory bulb and tract.
Name structures on the right side of the image
Age of cells in more superficial layers of cerebral cortex
Younger, they pass superficially and form connections with the cells they pass.
Neuronal cell morphology
Stellate, fusiform, pyramidal
Allocortex
Three layers, located in the olfactory cortex, hippocampus and dentate gyrus
External pyramidal layer projections
Commissural and ipsilateral cortico-cortical association fibres
Internal pyramidal layer projections
Main efferents to the brainstem and spinal cord
Broadman area
123
Location
Post-central gyrus
Broadman area
123
Functional area
1o somatosensory cortex
Broadman area
123
Function
Touch
Brodman area
4
Location
Precentral gyrus
Brodman area
4
Functional area
1o motor cortex
Brodman area
4
Function
Voluntary motor control
Brodman area
5
Location
Superior parietal lobule
Brodman area
5
Functional area
3o somatosensory cortex
Posterior parietal association
Brodman area
5
Function
Stereognosis
Brodman area
6
Location
Precentral gyrus and rostral adjacent cortex- SMA and premotor area.
Brodman area
6
Functional area
Supplementatry motor control
Supplemental eye field
Premotor adjacent cortex
Supplementary eye field adjacent cortex
Brodman area
6
Function
Limb and eye movement planning
Brodman area
7
Location
Superior parietal lobule
Brodman area
7
Functional area
Posterior parietal association
Brodman area
7
Function
Visuomotor control
Perception
Brodman area
8
Location
Superior, middle, frontal gyri
Medial frontal lobe
Brodman area
8
Functional area
FEF
Brodman area
8
Function
Saccadic eye movements
Brodman area
9, 10, 11, 12
Location
Superior, middle frontal gyri
Medial frontal lobe
Brodman area
9, 10, 11, 12
Functional area
Prefrontal association cortex
Frontal eye fields
Brodman area
9, 10, 11, 12
Function
Thought
Cognition
Movement planning
Brodman area
13, 14, 15, 16
Location
Insular cortex
Brodman area
17
Location
Banks of calcarine sulcus
Brodman area
17
Functional area
Primary visual cortex
Brodman area
17
Function
Vision
Brodman area
18
Location
Medial and lateral occipital gyri
Brodman area 18
Functional area
Secondary visual cortex
Brodman area 18
Function
Vision, depth
Brodman area 19
Location
Medial and lateral occipital gyri
Brodman area 19
Functional area
Tertiary visual cortex
Middle temporal visual area
Brodman area 19
Function
Vision, colour, motion, depth
Brodman area 20
Location
Inferior temporal gyrus
Brodman area 20
Functional area
Visual inferotemporal area
Brodman area 20
Function
Form vision
Brodman area 21
Location
Middle temporal gyrus
Brodman area 21
Functional area
Visual inferotemporal area
Brodman area 21
Function
Form vision
Brodman area 22
Location
Superior temporal gyrus
Brodman area 22
Functional area
Higher order auditory cortex
Brodman area 22
Function
Hearing speech
Brodman area
23, 24, 25, 26, 27
Location
Cingulate gyrus
Subcallosal area
Retrosplenial area
Parahippocampal gyrus
Brodman area
23, 24, 25, 26, 27
Functional area
Limbic association cortex
Brodman area
23, 24, 25, 26, 27
Function
Emotions
Brodman area
28
Location
Parahippocampal gyrus
Brodman area
28
Functional area
Primary olfactory cortex
Limbic association cortex
Brodman area 28
Function
Smell, emotion
Brodman area
29, 30, 31, 32, 33
Location
Cingulate gyrus and limbic association cortex
Brodman area
29, 30, 31, 32, 33
Functional area
Limbic association cortex
Brodman area
29, 30, 31, 32, 33
Function
Emotions
Brodman area
34, 35, 36
Location
Parahippocampal gyrus
Brodman area
34, 35, 36
Functional area
Primary olfactory cortex
Limbic association cortex
Brodman area
34, 35, 36
Function
Smell, emotion
Brodman area
37
Location
Middle and inferior temporal gyri at temporo-occipital junction
Brodman area 37
Functional area
Parietal-temporal-occipital association cortex
Middle temporal visual area
Brodman area 37
Function
Perception, vision, reading, speech
Brodman area
38
Location
Temporal pole
Brodman area
38
Functional area
Primary olfactory cortex, limbic association cortex
Brodman area
38
Function
Smell, emotions
Brodman area
39
Location
Inferior parietal lobule (angular gyrus)
Brodman area
39
Functional area
Parietal-temporal-occipital association cortex
Brodman area
39
Function
Perception, vision, reading, speech
Brodman area
40
Location
Inferior parietal lobule (supramarginal gyrus)
Brodman area 40
Functional area
Parietal-temporal-occipital association cortex
Brodman area
40
Function
Perception, vision, reading, speech
Brodman area
41
Location
Heschl’s gyri and superior temporal gyrus
Brodman area
41
Functional area
Primary auditory cortex
Brodman area
41
Function
Hearing
Brodman area 42
Location
Heschl’s gyrus and superior temporal gyrus
Brodman area 42
Functional area
Secondary auditory cortex
Brodman area 42
Function
Hearing
Brodman area 43
Location
Insular cortex
Frontoparietal operculum
Brodman area 43
Functional area
Gustatory cortex
Brodman area 43
Function
Taste
Brodman area 44
Location
Inferior frontal gyrus (frontal operculum)
Brodman area 44
Functional area
Broca’s area
Lateral premotor cortex
Brodman area 44
Function
Speech, movement planning
Brodman area 45
Location
Inferior frontal gyrus (frontal operculum)
Brodman area 45
Functional area
Prefrontal association cortex
Brodman area 45
Function
Thought, cognition, planing behaviour
Brodman area 46
Location
Middle frontal gyrus
Brodman area 46
Functional area
Prefrontal association cortex (dorsolateral prefrontal cortex)
Brodman area 46
Function
Thought, cognition, planning behaviour, eye movement
Brodman area 47
Location
Inferior frontal gyrus (frontal operculum)
Brodman area 47
Functional area
Prefrontal association cortex
Brodman area 47
Function
Thought, cognition, planning, behaviour
What are the main sensory cortices
Somatosensory (1, 2, 3)
Visual (17)
Auditory (41, 42)
Gustatory (43)
Olfactory (not distinctly localised) 34
How did Brodman map the brain?
Topographical analysis of cortical cytoarchitecture
Location of primary somatosensory area
Post-central gyrus (3, 1, 2)
Inputs to the primary somatosensory area
VPL and VPM thalamic nuclei (medial lemniscus, spinothalamic and trigeminothalamic tracts)
Input for 1: muscle spindles and skin
Input for 2: Deep (joint) receptors
Input for area 3a: Muscle spindles
Course of fibres to primary somatosensory area
ML/STT-> VPLc/VPM- > S1
Draw the sensory homunculus
What to note
Face and tongue have bilateral representation
Location of secondary somatosensory area
Located on the superior bank of the lateral sulcus
Input to secondary somatosensory area
Ipsilateral VPLc and VPM thalamic nuclei
Bilateral S1
Output secondary somatosensory area
Ipsilateral S1 and motor cortex
Difference between primary and secondary somatosensory areas
The secondary somatosensory area receives bilateral fibres from the entire body, most of its fibres come from the primary somatosensory area
Body is bilaterally represented in the 2o with the leg most posterior and the face anterior which is the reverse of the primary somatosensory cortex
Location of the somatosensory association area
Superior parietal lobule (5, 7)
Function of somatosensory association areas
Integrates sensory data
Lesion causes tactile agnosias or astereognosis
Location of 1o visual cortex
Located in the walls and floors of the calcarine sulcus, extends around the occipital pole (17)
1o visual cortex
Input and output
Input-LGN with geniculocalcarine passing in the outer wall of the lateral ventricle to the calcarine sulcus (external sagittal stratum)
Output- Internal sagittal stratum-> cortifcofugal fibres-> superior colliculus and LGB
Visual vertical meridian cortical region
Has commissural fibres for bilateral representation
Ganglion cell receptive field
A region of the retina that affects the firing of one retinal ganglion cell
It is either on centre and off surround or on surround and off centre
Band of Baillarger
In striate cortex- stripe of Gennari which are collaterals of the primary visual cortical axons in layer IVb
Input on 2o visual cortex
LGB and pulvinar
Lesion of 2o visual cortex
Causes visual agnosia
Location of the transverse gyri of Heschl
Superior temporal gyrus, buried in the temporal operculum of the Sylvian fissure
1o auditory cortex
Input-output
MGB fibres passing through the sublenticular internal capsule
Each cochlea projects bilaterally but more to the contralateral side.
The trapezoid body is the only auditory commissure needed for sound localisation
Input on gustatory area
Ipsilateral nucleus solitarius-> VPMpc-> area 43
Location of the vestibular cortex
Inferior parietal cortex
Bilaterally represented
What are the main motor areas of cortex
1o motor area
Premotor area
SMA
FEF
Draw the motor homunculus
Location of 1o motor cortex
Precentral gyrus, involved in voluntary motor control
Cellular make up of the 1o motor cortex
Pyramidal cells of Betz make up 3% of the corticospinal fibres
Columns may be present
Not somatotopic
Unilateral projection except bilateral to eye, face, tongue
Neurotransmitters in 1o motor cortex
Glutamate and aspartate
Premotor cortex location
Lateral aspect of the cortex, anterior to area 4
Function of premotor cortex
Voluntary motor control for responses dependent on sensory input
Input on premotor cortex
Cortical, VL and VA thalamic nuclei
Unilateral lesion of premotor cortex
No deficit
Location of the SMA
Medial aspect of the hemisphere, anterior to area 4, medial superior frontal gyrus
Function of SMA
Programming, planning and initiating of motor movements
Neurones are somatotopically organised
Input and output of SMA
Input bilateral
Output: ipsilateral areas 4, 6, 5 and 7
Contralateral M2, bilateral SC, caudate, putamen and thalamus
SMA lesion
Hemiparesis/plegia
Diminished spontaneous speech
May have volitional movement with effort
Location of FEF
Area 8
Rostral to the premotor area (caudal middle frontal gyrus)
Function of FEF
Initiates saccades
Stimulation causes contralateral eye deviation
Which Brodmann area controls ipsilateral pursuit?
Occipital eye centre (17)
Projections of FEF
riMLF
Interstitial nucleus of Cajal
PPRF
SC
Input to motor area
Ipsilateral VL and VLo -> M1
Contralateral cerebellum-> M1
Medial GP-> ipsilateral thalamic Va, VLo, CM-> M2 and premotor cortex
S1-> all of M1
M2-> M1 and premotor cortex
Motor cortex has reciprocal fibres with the thalamus
Surface marking of the Sylvian fissure
Point 3/4 of the way on a line over the SSS from the nasion to the inion
Mark the frontozygomatic point: 2.5cm along the orbital rim above the zygomatic arch
Sylvian fissure extends along the line connecting these two points
Angiographic localisation of the Sylvian point
Most posterior branch of the MA
Should be 5cm from the midline on an AP film and corresponds to the top of the insula
Surface marking of the Rolandic fissure
Mark the upper Rolandic point: 2cm posterior to the halfway point along the midline nasion/inion line (also measured as 2.5cm behind the pterion along the Sylvian line)
Mark the lower Rolandic point: junction between the line from the upper rolandic point to the mid-zygomatic arch and the Sylvian fissure line
Motor strip is usually 4-5cm behind the coronal suture
Wernicke’s area
Brodmann 22
Broca’s area
44, 45
Primary motor cortex
4
Primary somatosensory cortex
1, 2, 3
FEF
8
Primary auditory cortex
41, 42
Gustatory cortex
43
Primary visual cortex
17
Primary olfactory cortex
34
Components of the limbic system
Limbic lobe
Hippocampal formation
Amygdaloid nucleus
Hypothalamus
Anterior nucleus of the thalamus
Components of the limbic lobe
Subcallosal
Cingulate
Hippocampal gyri
Collectively these gyri form a ring around the rostral portion of the brainstem
Components of the hippocampal formation
Hippocampus
Dentate gyrus
Parahippocampal gyrus
Parts of the hippocampus
Head
Body
Tail
Overview of the structural arrangement of the hippocampus
Bilaminar archicortical structure consisting of Ammon’s horn (hippocampus proper) and dentate gyrus with one lamina rolled up in another
It is an intraventricular expansion of the temporal lobe cortex and forms the floor of the temporal horn of the lateral ventricle
Anteriorly it enlarges to form the pes hippocampus
Posteriorly it terminates beneath the splenium
Histological composition of hippocampus
Three-layered archicortex
Molecular layer
Pyramidal
Polymorphic
Afferent connections of the hippocampus
Entorhinal area
Septal area
Anterior thalamic nucleus
Mamillary bodies
Noradrenergic fibres from locus coeruleus
Serotonergic fibres from raphe nuclei
Fornix carries commissural fibres that originate in the hippocampus on the opposite side
Efferent connections of the hippocampus
Ventricular surface of hippocampus covered by alveus (WM) which contains fibres that originate in large pyramidal cells of the hippocampus, these converge on the medial border and continue posteriorly as the fimbria
Fimbria continues as crus of fornix which becomes crura to converge and form the body of the fornix
Forms two columns which terminate in the mamillary bodies
Also sends fibres to the anterior thalamic nucleus, midbrain reticular formation and contralateral hippocampus
Intrahippocampal connection
Perforant pathway connects the entorhinal cortex to dentate gyrus
Mossy fibres connect dentate to CA3
Schaffer collaterals connect CA3 to CA1
Fibres emerge from alveus to form fimbria and ultimately emerge posteriorly as the fornix
Dentate gyrus
A narrow band of cortex with a notched appearance
Located between the fimbriae of the hippocampus and parahippocampal gyrus
Continuous with uncus anteriorly and posteriorly with the indusium griseum
Archicortex histologically with a granule cell layer rather than pyramidal
All dentate gyrus efferents are confined to the hippocampal formation.
Parahippocampal gyrus
Located between hippocampal fissure and collateral sulcus
Continuous with hippocampal formation along the medial border of the temporal lobe
Neocortex though in the subiculum there is a transition between neocortex and archicortex
Parahippocampal gyrus
Amygdaloid nucleus
Large gray mass covered by rudimentary cortex
Located in the anterior pole of the temporal lobe, in front of and above the tip of the inferior horn of the lateral ventricle and just below the uncus of the parahippocampal gyrus
Amygdala
Nuclear groups of the amygdala
Corticomedial, just below the pyriform area of the temporal lobe and receives fibres from olfactory bulb and cortex
Basolateral- reciprocal connections with the visual, auditory, somatosensory cortices as well as the thalamus and brainstem reticular formation
Efferent output of the amygdaloid nucleus
Reciprocal fibres to sources of input
Stria terminalis to the hypothalamic nuclei, the fibres of which accompany the C-shaped caudate nucleus as it loops around the thalamus
Papez
American neurologist who described circuit in 1937 thought to be involved in emotion
Describe Papez circuit
Association areas of the prefrontal, parietal, temporal and occipital cortices send fibres to the cingulate gyrus
Cingulate gyrus to the parahyippocampal gyrus
Hippocampus
Information is then relayed via fornix to the mamillary bodies
Projected from mamillary bodies via mamillothalamic tract to the anterior nucleus of the thalamus
From thalamus to cingulate gyrus
What white matter bundle carries efferents from cingulate and parahippocampal gyri to the hippocampus as part of Papez circuit?
Cingulum
What is “a”
Cingulum bundle
Role of the hippocampus in memory
Recent memory- ability to learn and retrieve material after intervals of minutes, hours or days
The Hippocampus, mamillary bodies and dorsomedial nucleus of the thalamus are involved in this.
These structures appear to store and retrieve memories from the cerebral cortex
Lesions to these areas are marked by recent memory loss with preservation of immediate and remote memory
e.g. Korsakoff’s and surgical destruction of hippocampi (previously performed on patients with medically refractory epilepsy
Which structures are involved in Korsakoff’s
Bilateral destruction of mamillary bodies and dorsomedial nuclei
Function of amygdaloid nucleus
Concerned with emotions and autonomic consequences.
Receives afferents from areas of the cortex representing all sensory modalities
Effects mediated by the hypothalamus which receives amygdaloid efferents via stria terminalis
The patient noted rising epigastric sensation with a fleeting inexplicable sense of fear
Then observed to stare blankly into space and not responding to conversation
Then fumbled with her dress in a purposeless and uncoordinated manner, pale and sweaty with irregular breathing pattern.
Becomes responsive after 3 minutes and stops stereotyped fumbling
Amnestic for episode
Remains slightly confused for hours after the event.
Temporal lobe seizure
Clinically manifested by sensory, motor, psychic and autonomic manifestations.
The psychic and autonomic symptoms appear to arise as a result of abnormal discharge in amygdaloid nucelus
Henry Molaison
An American man who underwent bilateral medial temporal lobectomy in an attempt to cure epilepsy.
Consequently, he suffered from both anterograde and retrograde amnesia.
Retrograde amnesia improved but he was unable to form new memories or learn new information.
Resided in a care home from 1957 until his death.
What separates the cingulate gyrus from the corpus callosum
The callosal sulcus and indusium griseum
What are the only interneurones in the cerebral cortex that use glutamate?
Stellate cells.
All the other interneurones use GABA
Cells of Martinotti
Present at many levels of cortex, send axons that end in the most superficial layers of the cortex
Which areas of cortex do not receive commissural fibres from contralateral hemisphere
Hand and foot areas of somatosensory cortex
Primary visual cortex
Hippocampal commissure
Traverse midline inferior to the splenium of corpus callosum containing fibres that connect the posterior columns of the fornix
Frontal aslan tract
Connects posterior portion of the IFG to the SMA and pre-SMA
Impaired verbal fluency but preserved semantic processing (uncinate)
Identified in DTI studies in primary progressive aphasia which has both nonfluent and semantic variants.
Afferent connections of 1o motor cortex
Premotor area
Somatosensory cortex
VL nucleus of thalamus
Cortical representation SMA
Bilateral body representation
Face rostral, leg caudal
Features of SMA syndrome
Akinetic mutism with contralateral paresis
Not able to initiate voluntary movement but when passively initiated movement and strength are within normal limits.
The patient may localise with the affected arm
Can be differentiated from a CST lesion through preservation of tone in the affected arm (CST lesion would result in flaccid paralysis).
Premotor cortex and lesion
Concerned with planning and programming of movements.
Helps to store programs of motor activity that have been developed as a result of past experiences.
Lesions here may result in apraxia.
Def: apraxia
Impairment of movement execution in absence of paralysis
Location of secondary somatosensory cortex
Superior lip of posterior limb of lateral fissure
Representation of secondary somatosensory areas
Bilatearl cortical representation
Tonotopic organisation of 1o auditory cortex
Impulses related to low frequencies are located in anterolateral portion of cortex
Impulses related to high frequencies are located in the posteromedial cortex
Lesions involving primary auditory cortex
Bilateral projection of auditory tracts so lesions of auditory cortex result in a decrease in the perception of sound only
Right hemisphere syndromes
Constructional apraxia
Dressing apraxia
Neglect and Denial
Colour blindness
Constructional apraxia
Right hemisphere syndrome
Inability to draw or costruct 2 or 3 dimensional objects as a result of a disorder in learned movements.
Right parietal lesion
Localisation:
Constructional apraxia
Right parietal lesions (non-dominant)
Dressing apraxia
Unable to properly clothe self.
May involving leaving the left side partly undressed
Right parietal lesion (non-dominant)
Localisation;
Dressing apraxia
Right parietal (non-dominant)
Neglect and denial
Patient with neglect tends to neglect half the space contralateral to the lesion e.g. clock with numbers crowded onto the side of the lesion or only shave half of the face.
Denial disorder- can result in anosognosia
Non-dominant hemisphere lesions
Colour blindness
Achromatopsia
Cannot sort colours according to hue
Can be a result of the bilateral or non-dominant inferior occipitotemporal lesion
Different from colour agnosia
Lesion spares primary visual cortex.
Non-dominant occipital lobe
Colour agnosia
Inability to name or point to colours without ability to sort colours according to hue (which would be colour blindness)
Dominant hemisphere
Localisation: Colour blindness
Non-dominant occipital lobe
Dominant hemisphere syndromes
Dysphasia
Apraxias:
Ideational
Ideomotor
Agnosia:
Visual
Colour
Alexia without agraphia
Gerstmann’s:
Left right disorientation
Finger anomia
Dyscalculia
Agraphia
Ideomotor apraxia
Inability to perform previously learned motor acts that cannot be explained by disturbances in sensation, strength or comprehension
Involves Wernicke’s area conveyed via arcuate fasciculus to the premotor cortex in frontal lobe either right or left (bilateral representation)
Dominant hemisphere
Ideomotor- inability to perform single task e.g. can’t comb hair with comb
Ideational- inability to perform correct sequences of task e.g. to brush teeth.
Best way to test for ideomotor apraxia
Ask the patient to brush hair or clean teeth
Typically demonstrate errors such as gripping toothbrush inaccurately or failing to open mouth etc.
Visual agnosia
Inability to recognise objects visually in absence of disturbance of visual acuity or general intellectual function
Can either be as a result of a defect in visual perception (unable to name objects pointed to or nameed)- bilateral visual association area or visual association (unable to name objects but may be able to point at them or draw them)- bilateral inferior occipitotemporal lobes or dominant occipital lobe and crorpus callosum
Most patients who have visual agnosia are alexic
Alexia without agraphia
Affected individual is unable to read but can write
Dominant occipital cortex and posterior corpus callosum
Alexia is due to the disconnection of the dominant inferior parietal lobule which is responsible for processing auditory and visual information necessary for reading and writing is disconnected.
The patient is able to write as the inferior parietal lobule itself is preserved.
Localisation:
Alexia without agraphia
Dominant occipital lobe and posterior corpus callosum
Gerstmann’s syndrome
Dyscalculia
Finger agnosia
Left-right disorientation
Agrapiha
Dominant parietal lesion
Bihemsipheric syndromes
Ideational apraxia
Anton’s syndrome
Ideational apraxia
Defect in motor planning of a higher order than that associated with ideomotor apraxia
Patients are able to perform individual motor acts but are unable to coordinate the complex sequences of acts that constitute everyday motor tasks.
e.g. may be able to light a match or put cigarette in mouth but unable to perform the full sequence from taking cigarette from packet to lighting it
Key to localisation of weakness to the cortex
“Cortical findings” i.e. aphasia, astereognosis, anosognosia, homonymous VF defects
How to discriminate between cortical and subcortical CTS disruption
Absence of cortical findings
LMN syndrome with the absence of sensory involvement localises to
Anterior horn cell or anterior spinal root prior to the exit of the spinal canal or purely motor peripheral nerve
Ideational apraxia
Failure to conceive and act, either when commanded or sponatneously
Ideomotor apraxia
Ability to conceive of motor action to be executed but inability to act
How to differentiate between ideational and ideomotor apraxia
Patient may be observed performing simple tasks e.g. dressing/washing/shaving- inability to perform these would be manifestation of ideomotor apraxia
Inability to perform complex learned tasks e.g. hammering nail or opening door would be considered ideational apraxia
Stages of central herniation
Cheyne-Stokes Respiratory
Small pupils
Intact VOR
Appropriate motor response
Dicencephalic stage
Stages of central herniation
Sustained regular hyperventilation
Midposition irregular pupils or unilateral blown
Dyconjugate gaze with impaired VOR
Decerebrate posturing
Midbrain-upper pons
Stages of central herniation
Ataxic or eupnic breathing
Midposition or fixed pupils
Absent VOR
No motor response
B/L upgoing plantars
Lower-pons/medullary stage
Stages of central herniation
Apnoeic episodes
Irregular pulse
Hypotension
No motor response
Medullary stage
Pattern of sensory deficit cortical vs subcortical
Cortical sensory deficits tend to produce relatively mild hemisyndromes primarily affecting arm and face or leg (MCA vs ACA)
Because motor and sensory fibres converge as they pass through deep subcortical structures, subcortical injuries tend to produce dense hemisyndromes affecting face, arm, leg.
How to test simultagnosia
Can interpret individual components of image but not wider picture.
i.e. can see trees but not forest
Can test with Ishihara colour plates- will see colour but not number
Part of Balint’s syndrome
https://www.youtube.com/watch?v=A8BD5liH7ug
How to test optic ataxia
Mislocalisation in space, hold a pen out they will miss but they can touch their own finger i.e. not cerebellar
Part of Balint’s
https://www.youtube.com/watch?v=A8BD5liH7ug
Hodotopic frame concept
Catani et al concept
Includes both topological (i.e. cortical functional epicentres) and hodological (connectivity between areas) views for understandng brain function
i.e. Cortex and white matter as a network
Extent of lesion in Broca’s dysphasia
Injury to the cortical area may not cause Broca’s dysphasia but a transient speech disorder
Broca’s dysphasia occurs with injury to Broca’s, middle inferior PreCG and WM underneath
Two major streams in the hodological model of language
Dorsal stream
Ventral steam
Function of dorsal stream
Phonological processing
Components of dorsal stream
Two layers:
Superficial
SLF: II- III and temporoparietal
Deep:
Arcuate fasciculus
Function of ventral stream
Semantic processing
Components of the ventral stream
Intra-temporal network:
MLF
ILF
IFOF
Role of frontal-aslan tract in the dual-stream model of language
Driving of speech
Initiation and speech spontaneity
Structures connected by IFOF
Two layers
Superficial: superior parietal lobule, Wernicke’s occipital association area and fusiform area at the occipitotemporal gyrus to IFG
Deep:
Originates in similar areas and terminates in multiple areas including orbitofrontal, MFG and dorsolateral PFC.
Rhinal sulcus
Medial temporal lobe
Semilunar gyrus
Semi-annular sulcus
Ambient gyrus
Uncinate gyrus
Infolded head of hippocampus
Anterior part of parahippocampal gyrus
Intralimbic gyrus- part of dentate gyrus
Band of Giocamini
Tail of dentate gyrus
View from medial→ lateral into temporal horn of lateral ventricle, green= uncal sulcus between hippocampus (yellow) and amygdala
Parahippocampal surfaces
Rhoton describes three surfaces of the parahippocampal- lower against tent/middle fossa, rounded medial surface, upper surface medial to the dentate gyrus. The PCA can run on the upper surface of the parahippocampal gyrus
With a subtemporal approach to reach the upper surface of parahippocampal gyrus is likely to require significant traction on temporal lobe
Ventricular relation to cerebral convexity:
Frontal horn
Inferior frontal gyrus
Ventricular relation to cerebral convexity:
Atrium
Supramarginal gyrus
Ventricular relation to cerebral convexity:
Temporal horn
Medial temporal gyrus
Cranial location of the foramen of Monro
Deep to a point 2cm above pterion, behind the lower third of the coronal suture
Ventricular relation to cerebral convexity:
Foramen of Monro
Deep to central part of pars opercularis of IFG
Cerebral hemisphere:
3 surfaces
Lateral
Medial
Basal
Cerebral hemisphere:
3 margins
Superior
Inferior
Medial
Cerebral hemisphere:
3 poles
Frontal
Temporal
Occipital
Cerebral hemisphere:
3 types of WM
Projection
Commissural
Association
Cerebral hemisphere:
5 lobes
Frontal
Parietal
Temporal
Occipital
Insular
What is useful for identifying the precentral gyrus during Sylvian split?
Pars opercularis which is located just anterior to the precentral gyrus and gyral bridge (red arrow) which commonly prevents the central sulcus from opening directly onto the Sylvian fissure
What is useful for identifying the post-central gyrus
The anterior bank of the supramarginal gyrus is just behind the post-central sulcus
The supramarginal gyrus is where the Sylvian fissure terminates
Limen insulae
Trans: Threshold to insula
Forms the junction point between anterior and posterior stem of the lateral sulcus.
Lateral limit of anterior perforated substance
Point at which the insular cortex is continuous with cortex over the amygdala and superior temporal gyrus.
Sulci of insular
Circular sulcus defines the limit
Central sulcus separates short from long gyri
Short insular gyri
Deep to pars triangularis and opercularis
Cortical landmark for foramen of Monro
Deep to a point on pars opercularis
1cm above Sylvian fissure
Deep to the midlevel of the short gyri of the insular
What separates cuneus and lingula?
Calcarine sulcus
Calcar avis
Prominence in the lower part of medial atrial wall overlying calcarine sulcus
Inferior choroidal point
The inferior extent of the choroidal fissure (cleft between thalamus and fornix)
Located just behind the head of hippocampus›
Opening the choroidal fissure between pulvinar and crus of fornix exposes
Quadrigeminal cistern
Opening choroidal fissure between lower surface of thalamus and fimbria of fornix exposes
Ambient cistern
Opening choroidal fissure adjacent to body of fornix exposes
Third ventricle
What marks the lower edge of velum interpositum in the third ventricle?
Striae medullaris thalami
The posterior border of the parietal lobe on the lateral surface
Upper half of a line from impression of upper end of parieto-occipital sulcus to the pre-occipital notch
Surfaces of frontal lobe
4
Lateral
Medial
Basal
Sylvian
Inferior gyri of the temporal lobe from medial to lateral
Parahippocampal
(collateral and rhinal sulcus)
Occipitotemporal (fusiform gyrus)
(occipitotemporal sulcus)
Inferior temporal
Isthmus of cingulate gyrus
Narrow strip of cortex at posterior end of parahippocampal gyrus
Wraps round splenium and connects the posterior end of parahippocampal gyri with cingulate gyrus
What sulcus separates precuneus and cingulate gyrus?
Subparietal sulcus
Gyri of the inferior surface of the occipital lobe
Lower part of lingula
Inferior occipital gyrus
Posterior part of occipitotemporal gyrus
Groups of cerebral sulci
Classified by Ono et al into three groups:
Those that are commonly continuous or uniterrupted
Low interruption rates
Regularly interrupted
Uniformly continuous sulci
Sylvian Fissure
Callosal
Parieto-occipital sulci
Highly continuous sulci
Central
Collateral
Calcarine sulci
Parts of Sylvian fissure
Superficial
Deep
Organisation of superficial Sylvian fissure
Stem and 3 rami
Stem begins medially at ACP. and extends laterally along the sphenoid ridge to the pterion where it divides into anterior horizontal, anterior ascending and posterior rami
Organisation of deep Sylvian fissure
AKA Sylvian cistern
Sphenoidal compartment
Operculoinsular compartment
Extent of sphenoidal compartment of Sylivan fissure
Extneds laterally from cistern around the ICA between frontal and temporal lobes
Roof of sphenoidal compartment of Sylvian
Posterior part of the orbital surface of the frontal lobe and anterior perforated surface
Caudate, lentiform and anterior limb of internal capsule are located above roof
Floor of the sphenoidal compartment of Sylvian fissure
Anterior part of planum polare, area free of gyri on upper temporal pole
Uncus located at medial part of floor
What underlies the limen insulae
The cingulum
How does the sphenoidal compartment communicate medially?
Through the Sylvian vallecula, tubular opening between the medial end of the temporal and frontal lips of the fissure to communicate with the opticocarotid cisterns
Etymology: Vallecula
Valley
https://link.springer.com/chapter/10.1007/978-3-030-54879-7_26
Borders of anterior perforated substance
Anterior: olfactory striae
Posterior: optic tract and stem of temporal lobe
Medial: interhemispheric fissure
Laterally: limen insula
Anterior segment of uncus faces
Anterior perforated substance
Posterior segment of uncus faces
Cerebral peduncle
Location of posterior perforated substance
Between the cerebral peduncles
Planum temporale
Posterior part of the upper surface of the temporal lobe
Made up of the transverse temporal gyri
Planum polare
The anterior part of the upper surface of the temporal lobe
Free of gyri and has a shallow trough to accommodate the MCA.
Stem of temporal lobe
Thin layer of gray and white matter that connects the temporal lobe to the lower insula
Position above the lateral and anterior edge of the temporal horn
Passage of optic radiations from LGB in temporal lobe
Pass laterally from LGB and course in roof of temporal horn along temporal stem and lateral to atrium to reach the calcarine surface
Portions of operculoinsular compartment of sylvian fissure
Two narrow clefts, opercular and insular
Opercular cleft
Portion of operculoinsular compartment of Sylvian fissure
Situated where the sylvian surfaces of the frontal lobe and parietal lobe face the sylvian surface of temporal lobe below
Insular cleft
Part of operculoinsular cleft of Sylvian fissure
Has a superior limb- located between the insula and opercula of the frontal and parietal lobes
Inferior limb located between insula and temporal operculum.
What structures form the upper lip of opercular cleft
Frontal gyri:
Pars orbitalis, triangularis, opercularis, precentral
Parietal gyri:
Post-central and supramarginal gyrus
What structures form the lower lip of the opercular cleft
Planum temporale
Planum polare
Sylvian point
Medially directed arterial apex
Formed by the most posterior MCA branch turning sharply away from the insula pointing towards the atrium
When is the insula visualised during sylvian dissection
Only when the lips of the fissure are widely separated, except in the area below the inferior angle of the pars triagnularis which can be attracted to expose a small area of the insular surface
Where is it safest to begin opening fissure
The natural upward retraction of pars triangularis creates the largest opening in the superficial compartment of the Sylvian fissure and provides an area where the fissure is widest
What is the floor of the anterior half of the basal ganglia
The anterior perforated substance
What sulcus demarcates the insula
Circular sulcus
Location of limen insula
Slightly raised area overlying uncinate fasciculus
Lateral border of the anterior perforated substance
Located at the junction of the sphenoidal and operculoinsular compartments
Insular apex
Anteroinferior angle of the insula
Located below the apex of the pars triangularis
Anterosuperior angle of insula points to
Sylvian point
Divisions of insula
Separated into an anterior and posterior part by the central sulcus of insula
Anterior:
3-5 short gyri
Posterior:
anterior and posterior long gyri
Superior temporal sulcus corresponds to which portion of the insula
Lower border
What is deep to the lower border of the insula
Optic tract coursing in the roof of the ambient cistern near the midline
Divisions of the central sulcus
Superior curve
Inferior curve
Together they form an inverted letter S
Inferior frontal convolution
Portion of frontal lobe that constitues pars orbitalis, triangularis and opercularis
Relationship of precentral gyrus to ventricle
Located lateral to the posterior part of the body of the ventricle
Relationship of postcentral gyrus to ventricle
Lateral to anterior part of atrium
What separates the middle frontal gyrus and cingulate gyrus?
The deep white matter forming the centrum semiovale
Relation of inferior frontal sulcus to corpus callosum
Located at the level of the upper margin of the anterior part of corpus callosum
Extended Sylvian
Demarcates lower border of the parietal lobe, extending posteriorly along axis of sylvian fissure
Depth of intraparietal surface is directed towards what strutcture
Roof of the atrium and occipital horn
Constituents of the inferior parietal lobule
Anterior supramarginal gyrus
Posterior angular gyrus
Which bit of cortex is lateral to the atrium of the lateral ventricle
Supramarginal gyrus
Lamboid sutures approiximate which cortical portion
Parieto-occipital junction
Approximate lateral cortical landmark of the calcarine sulcus
Level of a line extending posteriorly along the long axis of the superior temporal sulcus
Which structures are deep to the middle temporal gyrus
Temporal horn, ambient and crural cisterns
Location of ascending ramus of the cingulate sulcus
Between the paracentral lobule and precuneus
Location of precuneus
Between the paracentral lobule and parieto-occipital sulcus
Etymology: cuneus
Wedge
Location of cuneus
Between parieto-occipital sulcus and calcarine sulcus
Location of lingual gyrus
Below the calcarine sulcus
Location of paraterminal/paraolfactory gyrus
Below rostrum of corpus callosum
Relationship of corpus callosum to ventricular system
Genu wraps around frontal horn
Body form roof of body of lateral ventricle
Splenium adjacent to atrium
Bulb of corpus callosum
Prominence in the medial wall of atrium formed by the forceps major passing posteriorly from the splenium of corpus.
Stria terminalis
Courses between the caudate and thalamus
What separates the sublenticular optic and auditory radiations from the temporal horn?
Tapetum
What separates cingulate gyrus from precuneus and parietal lobe?
Subparietal sulcus
Subparietal sulcus
Posterior continuation of cingulate sulcus behind marginal ramus
Paracentral ramus of cingulate sulcus
Ascends at the midportion of corpus callosum to separate SFG from paracentral lobule
Marginal ramus of cingulate sulcus
Ascends at the level of the posterior 1/3rd of corpus callosum and separates the paracentral lobule from the precuneus
Paraterminal gyrus
Narrow triangle of gray matter in front of the lateral edge of lamina terminalis that is continuous with indusium griseum
What separates the paraterminal gyrus from the paraolfactory gyrus?
By the shallow posterior paraolfactory sulcus
What structures does the anterior paraolfactory sulcus separate
The paraolfactory gyrus from anterior part of frontal pole
Borders of precuneus
Anterior- marginal sulcus
Posteriorly- parieto-occipital suclus
Inferiorly- subparietal sulcus
Cortical landmark of subparietal sulcus
Located approximately at the level of the intraparietal sulcus
Location of striate cortex on calacarine sulcus
Part posterior to the junction with parieto-occipital sulcus has striate cortex on upper and lower lips
Anterior to the junction it is on the lower lip only
Fasciolar gyrus
Dentate gyrus blends posteriorly behind the splenium and becomes continuous with indusium griseum
Parts of uncus
Two segments:
Anterior
Posterior:
Upper and lower
Relationship of the optic tract to uncus
Passes above the medial edge of the posterior segment in the crural cistern
Location of the nucleus basalis
Orbital surface of the frontal lobe below the anterior commissure
Location of nucleus accumbens
Anterior to the basalis
Into what does the upper margin of the amygdala blend
Into the globus pallidus
Inferior choroidal point
Lower end of choroidal fissure and attachment of choroid plexus in temporal horn
Lies just behind the head of the hippocampus
The point at which the anterior choroidal artery enters the lateral ventricle
Location of crural cistern
Between uncus segment and cerebral peduncle
What divides the posterior uncus into upper and lower parts
Uncal notch
What forms the upper part of the posterior uncus
Upper part is predominantly formed by the hippocampal head
What forms the lower part of the posterior uncus
Parahippocampal gyrus
Relation of optic tract to amygdala
Medial to junction of the amygdala with the globus pallidus
What are the prominences that correspond to the collateral sulcus
The collateral eminence in the floor of the temporal horn
Collateral trigone in the floor of the atrium
What lies medial to the apex of the uncus?
CN3
With what is the rhinal sulcus continuous?
Collateral sulcus
Distance of temporal horn from temporal pole
Approximately 2.5cm
What is the rough basicortical extent of frontal horn
Extend as far as the horizontal H of the orbital suclus anteriorly
Which vessels enter/exit the temporal horn at the inferior choroidal point?
Inferior ventricular vein exits
Anterior choroidal artery enters
What connects the central core to the remainder of the hemisphere and where is this found?
The cerebral isthmus
Located deep to circular sulcus of insular
Issues with opening isthmus at the lower edge of circular sulcus
Will give entry into the temporal horn but at the mid-point of the circular sulcus the incision will cross sub lenticular fibres containing the optic and auditory radiations where they leave LGB/MGB
Arrangement of central core gray matter at the level of anterior perforated substance
Caudate and lenticular nucleus are in continuity
Amygdala is in continuity with lenticular nucleus
These also blend into the nucleus basalis and accumbens
Which portion of the isthmus is safe
Opening anterior part of isthmus carries less risk
Yasargil and Wieser reach the amygdala for amygdalohippocampectomy using 1-2cm incision through circular sulcus and lower isthmus just behind limen insula
Location of stria terminalis
Arises in the amygdala and courses along the border between caudate nucleus and thalamus in wall of lateral ventricle deep to the thalamostriate vein
Location of uncinate fasciculus
Curves around stem of Sylvian fissure and connects the frontal and temporal lobes
Located at lateral edge of anterior perforated substance, bordering anteroinferior part of insula
Parts of uncinate fasciculus
Upper:
Unites gyri on the superolateral part of frontal lobe with lateral temporal gyri
Lower:
Unites gyri on orbital surface of frontal lobe with parahippocampal and other medial temporal gyri
Location of cingulum
Courses along medial aspect of cerebral hemisphere forming most of the WM of the cingulate gyri
Connects subcallosal, paraolfactory areas with cingulate gyrus, parahippocampal gyri
Location of SLF
Along upper and lateral border of lentiform nucleus and insula
Arches backward from frontal lobe lateral to internal capsule, through parietal + occipital lobe arch downward to reach temporal lobe
Relationship of the internal capsule to the lateral ventricle
Anterior limb is separated from frontal horn by the caudate
Posterior limb separated from the body by the thalamus
Genu reaches the ventricle at the level of the foramen of Monro
Location of subthalamic nucleus
Situated in interval between cerebral peduncle and midbrain
Relationship of SLF to optic radiations
The optic radiations are deep to the SLF
Relationship of SLF to extreme and external capsules
SLF is deep to the extreme and external capsules
Relationship of caudate to thalamus
Tail of caudate extends along the lateral edge of the thalamus
Why is the anterior limb of the internal capsule darker than posterior
There are bridges of transcapsular gray matter extending across the anterior limb of IC between caudate and lentiform nuclei
How do fibres from LGB reach the superior bank of calcarine fissure?
Leave upper part of LGB and course almost directly posterior around lateral aspect of the atrium to reach the visual cortex
How do fibres from LGB reach inferior bank of calcarine fissure
Pass from lower part of LGB looping forward and downwards into the temporal lobe, forming Meyer’s loop before turning back
Divisions of the optic radiation
Divided into anterior, middle and posterior groups
Anterior group of optic radiation
Meyer’s loop
Subserve upper half of visual field
Pass anteriorly along the roof of the temporal horn as far as tip and then loop along the lateral and inferior aspects of the atrium and occipital horn
Middle group of optic radiation
Subserve macula and course laterally above roof of temporal horn, turning posteriorly along the lateral wall of atrium and occipital horn
Posterior group of optic radiation
Pass directly backwards along lateral wall of atrium and occipital horn to end in the upper lip of calcarine fissure
Relation of SLF to insula
SLF courses in deep WM around outer edges of insula and lentiform nucleus
Which WM bundle lies deep to limen insula?
Uncinate faiculus
What is causing the white matter prominence marked by the red arrows?
The intersection of fibres of the corpus callosum and corona radiata
What is exposed through the window in the ventricular wall marked by the yellow arrow?
Window through calcar avis is exposing gray matter of calcarine suclus below
Relationship of the fornix to the foramen of Monro
Columns of fornix pass superior and anteriorly
Cortical landmark of anterior corpus callosum
In the midline, deep to the upper part of the inferior frontal gyrus
Cortical landmark of splenium of corpus callosum
Deep to supramarginal gyrus and lower third of a pre and post-central gyri
Parts of corpus callosum
Rostrum
Genu
Body
Splenium
Tapetum
What commissural fibres arise from the genu of the corpus callosum?
Forceps minor which forms the anterior wall of the frontal horn and interconnects frontal lobe
Which tracts arise from splenium of corpus callosum
Forceps major
Tapetum which sweeps inferolaterally to form the roof and lateral wall of atrium, temporal and occipital horns.
What structures are connected by the anterior commissure
Interconnects the olfactory structures and temporal gyri on both sides
Parts of the fornix
Fimbria
Crus
Body
Columns
What separates the fimbria from dentate gyrus?
Fimbriodentate sulcus
What separates the fimbria from the LGN and and optic/auditory radiations
Choroidal fissure
Where do the crurara of the fornix meet to form the body of the fornix?
At the junction between the atrium and body of lateral ventricle
Passes above thalamus and below septum pellicdum in lower part of medial wall of body of lateral ventricel
Where does the body of the fornix separate into the two columns
At the anterior margni of the foraemn of Monro
Where is the hippocampal commissure?
In the area below the splenium, interconnectinhte medial edges of the crura of the fornix
Relation of central sulcus to coronal suture
Normally 3.5-4.5cm behind
Parts of the choroidal fissure
Body part- between body of fornix and thalamus
Atrial part- between crus and pulvinar
Temporal part- between fimbria and stria terminais
Importance of choroid fissure
Allows access to third ventricle
In termporal region demarcates those structures located laterally that can be removed from those medially that should be preserved
Structure of the septum pellucidum
Streatches between the anterior corpus callosum and body of fornix
Paired laminae separating frontal horns and bodies of lateral ventricles in midline
Attachment of septum pellucidum in the frontal horn
Attached to the rostrum of corpus callosum below and genu above
Posteiror margin of septum pellicdum
Where the body of fornix meets splenium
Basis of cavum septum
Cavity in midline between the two laminae of septum
Location of kyehole
3cm anterior to pterion
Above the lateral end of superior orbital rim and under the most anterior point of attachment of the temporalis muscle and fascia to the temporal line.
What forms the posterior edge of the foramen on Monro?
The anterior thalamic tubercle which is the prominence overlying the anterior thalamic nucleus
What forms the lateral half o f the anterior wall of the atrium?
Pulvinar
What forms the anterior wall of the quadrigeminal cistern?
Pulvinar
Why is the central sulcus nearer to the coronal suture at its lower end than at its higher?
As it ascends it is directed more posteriorly
Cortical landmark of pineal gland
At the level of the posterior part of the middle temporal gyrus
Best transcortical approaches to cerebrum
Frontal lobe:
Middle or superior frontal gyri
Parietal loebe:
Superior parietal lobule
Intraparietal sulcus
Temporal:
Lower part of lateral or basal surface
Sulci suitable for apporaching deep lesions
Superior frontal
Inferior temporal
Occipitotemporal
Collateral
Intaraparietal sulci
Structures accessible via trans-sylvian dissection
Insula
Basal ganglia
Uncus
Orbit
Anterior cranial fossa
Olfactory
Optic
Oculomotor
Chiasmatic/interpeduncular/carotiod/lamina terminalis/crural cisterns
ICA, MCA and proximal ACA, basilar tip
Why does the posterior part of the interhemispheric cistern provide an excellent route to the quadrigeminal cistern
There are no bridging veins between posterior part of SSS and the occipital lobe
Structures accessible via subfrontal approach
Cribiform plate
Orbital roof
Optic nerves
Chiasmatic, lamina terminalis cisterns
Medial part of Sylvian fissure
Structures accessible via anterior subtemporal approach
Lesions along whole lateral margin of incisura back to the junction of ambient and quadrigeminal cisterns
Less risk with retraction as the basal bridging veins tend to be more posteriorly located
What are the three principle steps in temporal lobectomy
Lateral temporal exposure and removal
Medial disconnection of hippocampus
Anterior disconnection of hippocampus
Posterior disoconnection
Removal of remaining amygdala in front of uncal rescess
Etymology corpus callosum
Corpus meaning body
Callosum meaning tough
Etymology of fornix
Arch or vault
Etymology of sulcus
Furrow made with plow in Latin
Etymology parietal
From latin paries “wall”
