Neurology- anatomy Flashcards
Trace a drop of CSF to the subarachnoid space
:Produced by the ependymal cells of the choroid plexus
- lateral ventricles thru foramen of monroe to the 3rd ventricle
- 3rd ventricle thru cerebral aqueduct to the 4th ventricles
- 4th ventricle thru either lateral foramen of luschka or medial foramen of magendie to subarachnoid space
- subarachnoid space thru arachnoid granulations into dural sinuses
Describe the dural venous drainage
- superior sagital sinus
- the great vein of galen joins the inferior sagital sinus resulting in the straight sinus
- straight sinus + superior sagital sinus + occipital sinus join at the confluence of sinuses
- confluence of sinuses gives rise to the transverse sinuses –> sigmoid sinus –> internal jugular vein
Contents of cavernous sinus
: located on either side of the pituitary; collects blood from superficial cortex and eye and drains into the superior pertrosal sinus –> sigmoid sinus –> internal jugular
-contains branch of internal carotid a., CN III, IV, V1, V2, VI & post ganglionic sympathetic en route to orbit
Patient: Opthalmoplegia, decreased corneal and maxillary sensation with normal visual acuity
Cavernous sinus syndrome: usually due to mass effect, fistula, thrombosis
- CN VI most commonly affected
Recall: opthalmoplegia means weakness or paralysis of EOM
Anterior circulation of the brain
:result of the internal carotid; includes the ACA and MCA
- on the left ICA is a branch from the aortic arch
- on the right ICA is a branch off the brachiocephalic a.
Anterior cerebral artery
:ACA; supplies anteromedial surface of frontal and parietal lobe
-Lesion: contralateral paralysis leg > arm & contralateral sensory loss leg > arm
Middle cerebral artery
:supplies lateral surface of temporal and parietal lobes, optic radiations
-Lesion: Motor= contralateral arm, face paralysis; Sensory = contralateral arm and face loss of sensation; Optic radiations: homonymous hemianopsia; Speech= produce Broca’s or Wernickes aphasia (dominant hemisphere usually left); Hemineglect= contralateral neglect (usually right sided lesion, resulting in neglect of the left side)
Lenticulostriate artery
:branch of the MCA, supplies the striatum & internal capsule
-Lesion: contralateral hemiparesis/hemiplegia (weakness)
-Most common location of lacunar infarcts secondary to unmanaged hypertension
Posterior Circulation of the brain
: result of the vertebral arteries
- vertebral arteries arise as branches of the subclavian artery’s
- give rise to ASA, basilar artery, PICA, AICA, SCA, PCA
Anterior spinal artery
:supplies the lateral CST, medial lemniscus, caudal medulla = CN XII
Medial medullary syndrome
: contralateral hemiparesis, decreased contralateral proprioception, ipsilateral hypoglossal dysfunction (tongue deviates ipsilaterally)
-caused by infarct of paramedian branches of ASA and vertebral arteries
Posterior inferior cerebellar artery
:PICA; supplies posterior inferior cerebellum & lateral medulla = vestibular nuclei, lateral spinothalamic tract, descending (spinal) trigeminal nucleus, nucleus ambiguus, sympathetic fibers, inferior cerebellar peduncle
Lateral medullary syndrome
vomiting,vertigo, nystagmus, decreased in pain & temp (protopathic) sensation from ipsilateral face and contralateral body, dysphagia, hoarseness, decreased gag reflex, ipsilateral horner sundrome, ataxia, dysmetria
Note: nucleus ambiguus effects are specific to PICA
Anterior inferior cerebellar artery
:AICA; supplies middle and inferior cerebellar peduncles & lateral pons= CN nuclei, vestibular nuclei, facial nucleus, spinal trigeminal nucleus, cochlear nuclei, sympathetic fibers
Lateral pontine syndrome
: vomiting, vertigo, nystagmus, paralysis of face, decreased lacrimation and salivation, decreased taste from anterior 2/3 of tongue, decreased corneal reflex. Face - decreased pain and temp (protopathic) sensation. Ipsilateral diminished hearing, ipsilateral horner syndrome, ataxia, dysmetria
Note: facial nucleus effects are specific to AICA lesions
Posterior cerebral artery
:PCA; supplies occipital cortex, visual cortex
Lesion to PCA
:contralateral hemianopia with macular sparing
Basilar artery
:supplies pons, medulla, lower midbrain, CST, CBT, ocular cranial nerve nuclei, PPRF
Locked in syndrome
lesion to the basilar artery = preserved consciousness and blinking, quadaplegia, loss of voluntary facial, mouth and tongue movements
Anterior communicating artery
:ACom
- most common lesion is saccular (berry) aneurysm which can lead to a stroke
- usually results in visual field defects
Posterior communicating artery
: common site of saccular aneurysm leading to CN III palsy = eye is down and out with ptosis and pupil dilation
Limbic system
Structures include: hippocampus, amygdala, fornix, mamillary bodies and cingulate gyrus
Function: emotion, long-term memory, olfaction, behavior modulation, and autonomic nervous system
-major output is to the hypothalamus to control ANS and neuroendocrine secretions
Input to the cerebellum
- Contralateral cortex via middle cerebellar peduncle
- Ipsilateral proprioceptive information via inferior cerebellar peduncle from spinal cord (input nerves = climbing fibers and mossy fibers)
Cerebellar output
- Sends information to contralateral cortex to modulate movement
- output nerves = purkinje cells -> deep nuclei of cerebellum -> contralateral cortex via superior cerebellar peduncle
Deep nuclei of the cerebellum
Dentate, Emboliform, globose, fastigial
“dont eat greasy foods”
Lateral lesions of the cerebellum
propensity to fall toward injured (ipsilateral) side
Medial lesions of the cerebellum
:lesion of the vermis, fasigial nuclei) and/or flocculonodular lobe result in truncal ataxia, nystagmus and head tilting
- may have a wide based cerebellar gait and deficits in truncal coordination
- midline structures result in bilateral motor deficits affecting axial and proximal limb musculature
Papez circuit
hippocampus -> fornix -> mammillary bodies -> anterior nucleus of thalamus -> cingulate gyrus -> hippocampus
Structures of the basal ganglia
Striatum (caudate + putamen), globus pallidus, substantia nigra, subthalamus
Note: lentiform nucleus ( putamen + globus pallidus)
Direct pathway of basal ganglia
motor cortex (glutamate) --> striatum (GABA) --> inhibits globus pallidus interna = inhibiting an inhibitory signal -GPi communicates to thalamus via VL, so thalamus is free to communicate to motor cortex --> motor function carried out
What role does the Substantia nigra play in movement?
: activates the direct pathway via D1 dopamine receptors and inhibits the indirect pathway via D2 dopamine receptors
Indirect pathway of the basal ganglia
Motor cortex (glutamate) --> Striatum (GABA) -> inhibits GPe which disinhibits GPi (GABA) -> inhibits the thalamaus (VL) -so motor function not carried out
How does the subthalamus modulate movement?
Motor cortex (glutamate) -> activates subthalamus --> activates GPe -so motor function suppressed via inhibition of the thalamus mediated by GPe
Primitive reflexes
- present in healthy infant, disappear within 1st year
- inhibited by frontal lobe in mature adult; lesion to frontal lobe causes loss of inhibition
Moro reflex
abduct/extended limbs when started and then draw together
Rooting reflex
movement of head toward one side if cheek or mouth is stroked (nipple seeking)
Sucking reflex
sucking response when roof of mouth is touched
Galant reflex
Stroking along one side of the spine while newborn is in ventral suspension (face down) causes lateral flexion of lower body toward stimulated side
Plantar reflex
dorsiflexion of large toe and fanning of other toes with plantar stimulation = “babinski sign”
Outer ear
Visible portion ear (pinna), includes auditory canal and tympanic membrane
-transfers sound waves via vibration of TM
Middle ear
:air filled space with three bones called ossicles (malleus, incus, stapes)
-ossicles conduct and amplify sound from TM to inner ear
Inner ear
Snail shaped, fluid filled cochlea; contains basilar membrane that vibrates secondary to sound waves
-vibration transduced via specialized hair cells -> auditory nerve signaling -> brainstem
Low frequency (low pitch) sound detected where on the basilar membrane?
apex near helicotrema (wide and flexible)
High frequency sound heard detected where on the basilar membrane?
base, thin and rigid
