Neuro anatomy Flashcards
Medulla oblongata
Viewed from dorsal surface of brainstem - gracile (medial) and cuneate (lateral) tubercles, round swellings on either side of midline - contain dorsal column nuclei, ascending sensory tract pathways
Sensory
Dorsal column:
- fasciculus gracilis - T7 down
- fasciculus cuneatus - T6 up
- ipsilateral
- fine touch, vibration, proprioception
Spinocerebellar:
- proprioception
- to cerebellum
Spinothalamic tract (= anteroateral):
- contralateral
- to thalamus
- crude touch, pain, temperature
Three order neurones - 1st is DRG to medulla, 2nd is medulla to thalamus, 3rd is thalamus to post central gyrus
Fourth ventricle
Diamond shaped rhomboid fossa forms floor
Limits:
- lateral - middle cerebellar peduncle
- anterior - superior cerebellar peduncle
- posterior - gracile + cuneate tubercles
- inferior - obex
Tectum
Superior part of midbrain, above aqueduct
4 small swellings of grey matter, colliculi:
- superior colliculus for vision
- inferior colliculus for audio
- reflex movement towards sight/sound
Third ventricle
In diencephalon
- walls by thalamus and hypothalamus
+ epithalamus (containing pineal body) and subthalamus (both too small to see)
Thalamus
Symmetrical, two halves joined at interthalamic adhesion, flattened disc on medial surface
On either side of third ventricle
Each half is divided into anterior, medial, lateral parts by sheets of white matter
Contain nuclei for info to and from cerebral cortex
- specific nuclei to restricted cortical areas
- non-specific nuclei diffuse across cortex
Thalamic nuclei
Anterior nuclear group - from mamillary bodies to cingulate cortex (limbic system circuit of Papez)
Central posterior group - sensory information
Pineal body
In epithalamus
Endocrine gland
Synthesises melatonin
For circadian rhythm
Inhibitory effect on gonads
Often calcifies with age
Internal capsule
Contains cerebral cortical projection fibres
To and from frontal lobes - most anterior
Parietal fibres in between
To and from temporal/occipital lobes - posterior
Retrolenticular capsule: auditory to temporal (front), optic to occipital cortex (back)
Wraps around:
- caudate nucleus (head and tail)
- lentiform nucleus (inc globus pallidus and putamen)
- thalamus
- anterior and posterior horns of lateral ventricle
Somatosensory cortex
Primary - SI, Brodmann’s 1,2,3
- postcentral gyrus
- somatotopic representation of body
Secondary - SII
- extends posteriorly behind primary cortex down to lateral sulcus
Somatosensory association cortex - Brodmann’s 5
- posterior to primary cortex in superior part of parietal lobe
Brain cancer
15/100,000 new cases per year, prevalence increasing
50-70yo most common, but gliomas at any age
PRIMARY - 130 types, glioma most common
SECONDARY - 10x more common
- Skin Lung Kidney Breast Gastrointestinal
some love killing brain glioma
40% live to one year
Symptoms
- raised ICP - headache, papilloedema, nausea and vomiting
- focal neurological deficit - cranial nerve palsy, weakness
- seizure
Locations of brain tumours and their effects
FRONTAL - personality change, difficulty planning, hemiparesis
TEMPORAL - hallucinations, seizure, word finding difficulty
PARIETAL - aphasia, sensory loss, agnosia
CEREBELLAR - ataxia, poor coordination, vertigo, diplopia
OCCIPITAL - visual loss
PITUITARY - bitemporal visual loss, endocrine changes
Sensory peripheral neuropathy
Glove and stocking distribution
Affecting touch, pain, temperature
Motor cortex
Includes:
- primary motor cortex - Brodmann’s 4 - precentral gyrus and area immediately in front
- premotor cortex - Brodmann’s 6 - immediately in front and to lateral surface of motor cortex, close connections with it
- supplementary motor area - superior and medial surfaces of hemisphere above PMC
-> for voluntary movements of opposite side of body
upper/medial part - lower limb, perineum
lower/lateral part - trunk, upper limb, neck, head
Ventral pons and medulla
PONS
Groove (containing basilar artery) runs through
Middle cerebellar peduncles are striations out
MEDULLA
Partially divided by anterior median fissure
Pyramids immediately lateral to fissure on each side, mark position of underlying corticospinal/pyramidal tract fibres
80% corticospinal fibres decussate here
Olive to side of each pyramid - swellings containing inferior olivary nucleus, which are connected to contralateral cerebellar circuits to influence movement
Motor
Corticospinal tract (pyramidial):
- voluntary movement below neck (corticobulbar for above neck)
- in lateral tract, contralateral (90%)
- in anterior tract, ipsilateral (10%)
Rubrospinal tract:
- from red nucleus
- unimportant in humans, upper limb flexion?
Reticulospinal tract:
- from reticular formation
- for visceral functions eg awake, breathing, maintaining muscle tone
Vestibulospinal tract:
- from vestibular nuclei
- for anti-gravity posture, limb extensors
Tectospinal tract:
- from tectum
- for reflex movements of head and neck to visual and auditory stimuli
Basal nuclei
Caudate nucleus (comma shaped mass grey matter)- striatum
Putamen (darker, lateral) - striatum, lentiform nucleus
Globus pallidus (lighter, medial) - lentiform nucleus
Subthalamic nucleus
Substantia nigra - black line between crus cerebri, destroyed in Parksinson’s so no dopamine
Claustrum - immediately deep to insular cortex, separated by extreme capsule
-> for practise, planning movement, intitiating movement. Gatekeeper, to inhibit or allow movement.
Cerebellum
Hindbrain
Two ovoid hemispheres joined in midline by median vermis
Outer cortex - highly folded layer grey matter
Inner core - white matter surrounding deep nuclei
Primary fissure separates anterior and posterior lobes
Tonsils at base of cerebellum - if raised ICP then shift down, coning, into foramen magnum
Flocculo-nodular node (posterior lobe)
- floccules each side, nodule in middle
- vestibular information
Examining cerebellar function
DANISH P
D - dysdiadochokinesis
A - ataxic gait
N - nystagmus (towards side of lesion)
I - intention tremor
S - slurred speech (dysarthia)
H - hypotonia
P - past pointing (dysmetria)
All signs ipsilateral to lesion!
Meningitis
Purpuric (non-blanching) rash - leeching of RBCs from vessels
Pus accumulates at meninges, so raised ICP
Stretching neck is painful, reduced consciousness
Cranial nerves and their roots in the brain
Olfactory - forebrain
Optic - forebrain
Occulomotor - midbrain
Trochlear - midbrain
Trigeminal (opthalmic, maxillary, mandibular) - pons hindbrain
Abducens - pons hindbrain
Facial - medullary-pontine junction hindbrain
Vestibulocochlear - medullary-pontine junction hindbrain
Glossopharyngeal - medulla hindbrain
Vagus - medulla hindbrain
Accessory - medulla hindbrain
Hypoglossal - medulla hindbrain
Olfactory nerve
Through cribiform plate
Special sense of smell - sensory only
Anosmia caused by infection/inflammation, nasal polyps, head trauma + associated fracture, frontal tumour
Optic nerve
Through optic canal
Special sense of sight - sensory nerve only
Clinically assess acuity + colour vision, fundoscopy, light reflex, accomodation, visual fields
Lesions of visual pathways
Total blindness of one eye - ipsilateral optic nerve damage
Bitemporal hemianopsia (can only see middle) - optic chiasm
Ipsilateral nasal hemianopia (lost medial one side) - part of optic nerve cut
Contralateral hemianopsia (one side of both eyes lost) - optic tract
Occulomotor nerve
Through superior orbital fissure
Motor - symp and parasymp to all muscles of eye except LR6SO4
Clinically tested with light reflexes and assessment of eye movements
Palsy -> dilated pupil, unresponsive to light, no accomodation, down and out eye, ptosis
Palsy may be from aneurysm/atherosclerosis in basilar artery
Trochlear nerve
Through superior orbital fissure
Motor to superior oblique
Palsy -> diplopia, esp looking down
Trigeminal nerve
OPTHALMIC
- through superior orbital foramen
- sensation to upper face
MAXILLARY
- through foramen rotundum
- sensation to middle face
MANDIBULAR
- through foramen ovale
- sensation to jaw and temporal regions, anterior 2/3 tongue
- motor to muscles of mastication
Clinically assess - touch across face, clench jaw and feel muscles of mastication
Abducens nerve
Through superior orbital fissure
Motor to lateral rectus
Palsy -> unable to look laterally, diplopia
Facial nerve
Through internal auditory meatus and stylomastoid foramen
Sensory - taste to anterior 2/3 tongue
Motor - muscles of facial expression
Parasympathetic - salivary and lacrimal glands
Clinically assess - facial expressions x 5
UMN lesion -> forehead sparing
LMN lesion -> Bell’s palsy of whole face
Vestibulocochlear nerve
Through internal auditory meatus
Sensory - balance and auditory
Clinically assess - balance, Rhine’s test (conduction), Weber’s test (centre, localisation)
Glossopharyngeal nerve
Through jugular foramen
Sensory - pharynx and ear, taste and sensation to posterior 1/3 tongue
Motor - swallow, salivation to parotid
Clinically assess with vagus
Vagus nerve
Through jugular foramen
Sensory - pharynx, larynx, external ear, trachea, oesophagus
Motor - swallow, speech (recurrent laryngeal)
Parasymp - viscera
Clinically assess with glossopharyngeal - look for uvula deviated away from lesion, speech ok, watch swallow
Accessory nerve
Through jugular foramen
Two roots:
- cranial - joins vagus after leaving brainstem
- spinal - emerges then descends through foramen magnum
Motor - sternocleidomastoid, trapezius
Clinically assess - turn head, shrug shoulders against resistance
Hypoglossal nerve
Through hypoglossal canal
Motor - tongue
Clinically assess - tongue movements, push against cheek (tongue deviates towards affected side)
Sensory/motor function of cranial nerves
Sensory only - I, II, VIII
Motor only - III, IV, VI, XI, XII
Both - V, VII, IX, X
Eye
Bones of orbit: zygomatic most lateral, sphenoid, ethmoid, lacrimal, maxilla most medial and floor, + frontal bone above
6 muscle move eye
Levator palpebrae superioris opens eyelid controlled by occulomotor, orbicularis occuli closes controlled by facial nerve
3 layers over eyeball: sclera, choroid, retina
Ear
Information -> dorsal and ventral cochlear nuclei -> inferior colliculus -> medial geniculate nucleus -> auditory cortex
Tensor tympani and stapedius controlled by V3 trigeminal and branch of facial nerve, tense tympanic membrane to dampen sound
Malleus, then incus then stapes hits oval window, ossicles
Speech areas
Wernicke’s area - part of temporal lobe surrounding auditory cortex
- perception and understanding of speech
- lesions -> receptive aphasia
Broca’s area - inferior part of temporal lobe
- production of words (motor)
- lesions -> expressive aphasia
Superior speech cortex - supplementary motor area
Subarachnoid haemorrhage
Thunderclap headache - berry aneurysm bursts - regard as SAH until proven otherwise
10/10 pain, confusion, neck stiffness following
Associated with many other conditions
Brachial plexus
C5 and C6 -> superior trunk (suprascapular nerve arises)
C7 -> middle trunk
C8 and T1 -> inferior trunk
(long thoracic nerve arises from C5-7)
(dorsal scapular nerve arises straight from C5)
Branches from each -> posterior cord (superior subscapular, thoracodorsal, inferior subscapular arise here)
Superior trunk gains branch from middle, -> lateral cord (lateral pectoral nerve arises here)
Inferior trunk continues -> medial cord (medial pectoral, medial cutaneous of arm, medial cutaneous of forearm)
MUSCULOCUTANEOUS - from lateral cord
MEDIAN - from lateral and medial cords joining
AXILLARY - from posterior cord
RADIAL - from posterior cord
ULNAR - from medial cord
Clockwise from C4
C5, C6, C7, C8, T1
Long thoracic nerve
Superior subscapular, thoracodorsal, inferior subscapular
Medial pectoral, medial cutaneous of arm, medial cutaneous of forearm
Ulnar, Median, Radial, Axillary, Musculocutaneous
Lateral pectoral nerve
Terminal nerves, cords, divisions, trunks, roots
Causes and consequences of damage to nerves of the brachial plexus
Axillary - shoulder, eg dislocation -> numbness/weakness in shoulder, can’t abduct arm
Radial - mid humerus fracture -> wrist drop
Musculocutaneous - rare -> weak flexion and supination of forearm
Median - wrist -> loss of flexion in proximal and distal interphalangeal joints of digits 2 + 3
Ulnar - elbow (funny bone) -> claw hand, no fine motor control
Upper/lower brachial plexus injuries
UPPER
- neck stretched, eg fall from motorbike
- waiter’s tip
LOWER
- underarm stretched, eg hanging from tree
- claw hand
Terminal nerves of brachial plexus roots
Median and radial - all roots C5-T1
Lumbar plexus
L1-L5
I twice got laid on Friday:
Iliohypogastric (larger) - L1
Ilioinguinal - L1
Genitofemoral (through psoas) -L1-2
Lateral cutaneous (under inguinal ligament) - L2-3
Obturator (obturator foramen) - L2-4
Femoral (through femoral triangle) - L2-4
Sacral plexus
S1-4 (L4 + L5 join to form lumbosacral trunk)
Some irish sailor pesters Polly:
Superior gluteal - L4-S1
Inferior gluteal - L5-S2
SCIATIC (fibular (anterior/lateral) and tibial (posterior) parts) - L4-S3
Posterior femoral cutaneous (skin posterior thigh) - S1-3
Pudendal (reenters via lesser sciatic foramen) - S2-4 - ‘S234 keeps the shit off the floor’
All exit via greater sciatic foramen
Causes and consequences of damage to the lumbosacral plexus
FEMORAL - femoral triangle (hip fracture, psoas absess) -> weak quadriceps, numbness in medial thigh and anterolateral side leg
OBTURATOR - childbirth/pelvic/abdominal surgery -> parasthaesia + numbness of medial thigh, weak adduction, posture + gait problems
SCIATIC - slipped disc/intramuscular infection of buttock/damage in groin or knee -> weak knee flexion/plantar flexion/inversion
COMMON PERONEAL - Zenker’s paralysis (fracture of fibular neck) -> foot drop, dorsal + lateral sensation loss on foot
TIBIAL - knee dislocation, damage to popliteal fossa -> no plantarflexion or toe flexion, weak inversion
Compartments of the leg
ANTERIOR
- dorsiflexion, inversion (with posterior also)
- deep peroneal nerve
- anterior tibial artery
LATERAL
- eversion
- superficial peroneal nerve
- branch posterior tibial artery
POSTERIOR
- plantarflexion, inversion (with anterior also)
- tibial nerve
- branch posterior tibial artery
Upper and lower motor neurones
UMN
- from cerebral cortex and brainstem
- corticospinal and corticobulbar tracts are descending pathways to control LMNs
- lesions eg stroke, intracranial bleed, cerebral palsy, MS, traumatic brain injury
LMN
- cranial nerves from brainstem and spinal nerves from ventral horn of the spinal cord
- named nerves to specific muscles
- lesions eg MND, specific nerve palsy, peripheral neuropathy, poliomyelitis
Peripheral neurological exam
INSPECTION
TONE - increased UMN, decreased LMN lesion
POWER - decreased UMN, specific decrease LMN lesion
REFLEXES - brisk UMN, diminished LMN (Babinski sign UMN)
SENSATION
COORDINATION
+ clonus UMN, wasting/fasciculations LMN
Femoral nerve block
Local anaesthesia to femoral nerve supplying periosteum of femur
- after femur neck/shaft fracture, knee or hip surgery
CAREFUL - close proximity to major vessels
- patient supine
- draw line pubic tubercle to ASIS
- needle in 2cm below inguinal ligament, 1cm lateral to femoral artery
- feel two pops, fascia lata and fascia iliaca
- pull back, ensure not in artery or vein
- inject LA
Subdural haematoma
From moderate-severe blunt head trauma/falls
-> shearing injuries due to rotational or linear forces (likely tear of bridging veins between cortex and dural venous sinuses)
Presentation:
ACUTE - shortly after head injury
SUBACUTE - 3-7day delay - lucid interval, then deterioration and loss of consciousness
CHRONIC - 2-3week delay - gradual progression of anorexia, nausea + vomiting, neurological deficit
Worse in the elderly - cerebral atrophy puts pressure on veins - and in those with impaired clotting
CT shows crescent shape
Extradural haematoma
Likely middle meningeal artery ruptured, after blow to pterion
4x more likely in men, also in children and age 40-50 peaks
Presentation:
- high velocity head trauma
- loss of consciousness
- associated skull fracture
- lucid interval, then sudden deterioration
10-15% mortality!
Disc of blood pushing into brain tissue on CT
Association fibres
Run entirely in one hemisphere:
‘U’ (SHORT) FIBRES - between adjacent areas of cortex
SUPERIOR LONGITUDINAL FASCICULUS - in core of hemisphere, to connect frontal parietal and occipital lobes
CINGULUM - in cingulate gyrus extending to parahippocampal gyrus, to connect distant regions of cortex
INFERIOR LONGITUDINAL FASCICULUS - connect temporal and occipital lobes
+ external capsule - between claustrum and putamen
+ extreme capsule - between claustrum and insular cortex
Commissural fibres
To a) unite cerebral hemispheres, bring together the two halves of the body as well as auditory and visual fields and b) unite areas of cortex which function in only one hemisphere
CORPUS CALLOSUM - largest
- has genu (anterior), body, splenium (posterior), rostrum (inferior arch)
ANTERIOR COMMISSURE - thick bundle of white matter, between interventricular foramen to base of optic stalk/fornix
- crosses midline horizontally between lamina terminalis
POSTERIOR COMMISSURE - small bundle fibres at junction of midbrain to diencephalon, above tectum
- fibres between superior colliculi and pretectal nuclei (important for vertical movements of eye)
HIPPOCAMPAL COMMISSURE - at join of crus of fornix, cross midline inferior to splenium of corpus callosum
Projection fibres
INTERNAL CAPSULE
- corticopectal axons (originate outsie telencephalon, project to cerebral cortex)
- cortigofugal axons (arise from cerebral cortical cells, project to downstream targets)
Limbic system
Includes:
Hippocampus
Cingulate gyrus, cingulum, fornix
Hypothalamus + mamillary bodies
Amygdala
Circuit of Papez is the circle of connections:
Hippocampal formation ← Cingulate gyrus
↓ ↑
Mamillary bodies → Anterior nuclei of thalamus
For learning, memory, emotion
(affected in Alzheimer’s, schizophrenia, epilepsy)
Components of limbic system
Hippocampus
- rounded elevation in floor of inferior horn of lateral ventricle
- infolding of cortex, with grooves giving ‘paw-like’ appearance
- white matter fibres above stretch to become fornix
Cingulate gyrus + cingulum
- immediately dorsal (above) and parallel to corpus callosum
Fornix
- attached below septum pellucidum, fuse in midline and project back behind anterior commissure to mamillary bodies
Mamillary bodies
- contains mammillary nuclei of hypothalamus
Hypothalamus
- forms side wall and floor of third ventricle
- centre for homeostasis and control of autonomic and neuroendocrine systems
Amygdala
- anterior and slightly superior to anterior hippocampus
- receives major direct input from olfactory bulb
Ventricles
CSF produced by ependymal cells in choroid plexus, found in lateral, third and fourth ventricles
CSF is colourless, some protein, few cells
No -ve feedback system, so obstruction -> hydrocephaly
CSF enters subarachnoid spaces via lateral (foramen of Luschka) and medial (foramen of Magendie) apertures in 4th ventricle, then
CSF circulating around the brain is reabsorbed via arachnoid granulations mainly in superior sagittal sinus (higher hydrostatic pressure in subarachnoid space than in venous sinus system)
Hydrocephalus
Increased volume of CSF in ventricles
OBSTRUCTIVE = non-communicating
- obstruction in ventricles
- due to blood or space occupying lesion
NON-OBSTRUCTIVE = communicating
- usually reduced CSF reabsorption - infection, cancer
- rarely increased CSF production - choroid plexus papilloma
Symptoms of hydrocephalus
BABY (unfused sutures)
- fast head circumference growth
- irritable
- tense fontanelles
- increased tone, rigidity
- treat with surgery for ventriculostomy (drill hole in skull) or shunt to peritoneal cavity
ADULT (fused sutures)
- acute onset - headache, nausea + vomiting, papilloedema
- chronic (normal pressure hydrocephalus) - wet, wacky, wobbly (urinary incontinence, dementia, ataxia)
- treat acute onset with surgery for ventriculostomy (drill hole in skull) or shunt to peritoneal cavity
- treat normal pressure with repeated lumbar punctures (never acute, as -> coning, death)
Appearance of Alzheimer’s brain
CORTICAL ATROPHY:
Frontal - impaired executive function
Temporal - impaired language
HIPPOCAMPAL DESTRUCTION -> impaired memory
(appear enlarged ventricles)
Alcohol and memory
Disrupts formation of new long term memories by disrupting connections to and from hippocampus (established memories unaffected)
- dose-dependent
Chronic alcohol intake -> thiamine (B1) deficiency, -> direct damage to neurones and neuroglia
ACUTE PHASE - Wernicke’s encephalopathy
- ataxia, confusion, opthalmoplegia
- potentially reversible
CHRONIC PHASE - Korsakoff’s amnesia
- general cerebral atrophy -> amnesia, mamillary body damage -> confabulation, thalamic nuclei links to limbic system damage -> apathy
-> brain appears as in Alzheimer’s
Multiple sclerosis
Lesions disseminated in time and space
Optic nerve lesion -> reduced visual acuity
Internal capsule lesion -> paraesthesia and limb weakness
Brainstem/spinal cord lesion -> bladder dysfunction
Cerebellum lesion -> ataxia and tremor
