Brain Stem and Vascular Lesions Flashcards
all sympathetic pathways are 3 neuron pathways. where are the 3 neurons?
- first neuron of autonomic control always has cell body in hypothalamus- descend via descending hypothalamic axons
- preganglionic sympathetic neurons at T1-T3- these leave thoracolumbar spinal cord
- ascend up to superior cervical ganglia in sympathetic trunk
whole pathway is ipsilateral
sympathetic pathways are ipsilateral/ contralateral? What about parasympathetic pathways?
sympathetic- ipsilateral
parasympathetic- bilateral
the superior cervical ganglion provides all ____ input inside and outside of head
sympathetic innervation (3rd neuron in pathway)
what are the 3 “-osis” of Horner’s syndrome?
ptosis (eye droop), miosis (constricted pupil), anhydrosis (loss of sweating)
(loss of sympathetic input to face)
what lesion results in second order Horner’s syndrome?
lesion T1-T3 spinal nerve, 2nd nerve in 3 neuron system of sympathetic input. Carries sympathetic axons out of thoracolumbar spinal cord
considered peripheral Horner’s syndrome (since axons left thoracolumbar spinal cord)
a tumor presents with a tumor that results in third order Horner’s syndrome. what is being compressed?
superior cervical ganglion, 3rd neuron in 3 neuron pathway of sympathetic input
a patient presents with Horner’s syndrome and contralateral loss of limb and trunk pain and temperature sensation. what happened?
lesioned descending hypothalamospinal fibers (ipsilateral sympathetic input, loss causes Horner’s) and ascending spinothalamic tract (pain and temp, contralateral). both of these sets of fibers run along lateral brainstem in opposite directions
this would be central Horner’s if spinothalamic tract is also lesioned
the corticobulbar track descends alongside what other tract in the ventral and medial position in the brain stem?
runs parallel to corticospinal tract
corticobulbar tract arises from motor cortex that controls cranial nerve motor neurons
how does corticobulbar innervation differ from corticospinal innervation?
corticospinal crosses at pyramidal decussation and descends contralaterally
corticobulbar gives bilateral input to LMN
what is different about corticospinal and corticobulbar tracts, functionally (what they’re innervating)?
corticospinal- UMN to spinal cord. input to limb and trunk
corticobulbar- UMN to cranial nerves (“bulbar” is old word for brainstem). corticobulbar gives motor input for face, neck, head
T/F: a lesion in the corticobulbar fibers coming from one side of motor cortex will not result in deficit
TRUE: corticobulbar fibers are bilateral, so you’ll still have other side
the corticobulbar tract gives bilateral innervation except for:
facial motor nuclei. LMN that go to muscles used to wrinkle forehead/ shut eye are bilateral (top of face).
BUT LMN going to lower face (sphincters and dilators of nostrils and mouth) receive CONTRALATERAL innervation
(also, sternocleidomastoid of CN XI/ accessory gets ipsilateral input via corticobulbar)
how to tell the difference between a patient with a CN VII (facial nerve) lesion and lesion of corticobulbar tract?
VII lesion will show Bell’s Palsy- ipsilateral weakness of facial muscles
corticobulbar lesion- contralateral weakness of just lower face muscles (only corticobulbar neurons that are contralateral and not bilateral)
what’s different about the two muscles that are innervated by CN XI (accessory, motor)?
trapezius receives contralateral input (same UMN innervation as all other upper limb LMN, via corticospinal tract)
sternocleidomastoid receives ipsilateral input (via corticobulbar innervation)
entire brainstem and overlapping cerebellum is supplied (with blood) by medial and lateral branches of…..
vertebral basilar/ posterior circulation
the origins of the vertebral basilar circulation come from pair of vertebral arteries arising from subclavian of lower neck, entering cranial cavity through the….
foramen magnum
the ____ artery gives rise to bilateral branches that supply medial medullary vascular territory in brainstem
anterior spinal artery- arises from the medial and lateral branches of the vertebral circulation that come together
anterior spinal artery then gives rise to bilateral branches supplying medial medullary vascular territory
what is the PICA artery and what does it supply blood to
posterior inferior cerebellar artery- supplies lateral medulla and posterolateral cerebellum
at the pons-medulla junction, two vertebral arteries join together to form a single ___ artery that runs entire length of pons until pons-midbrain juncture where it splits into a pair of ____ arteries
at the pons-medulla junction, two vertebral arteries join together to form a single BASILAR artery that runs entire length of pons until pons-midbrain juncture where it splits into a pair of POSTERIOR CEREBRAL arteries
what are the lateral and medial branches of the basilar artery, which runs the length of the pons before splitting at the pons-midbrain juncture?
medial branches of basilar- paramedian branches, supply medial pons vascular territory
lateral branches of basilar- AICA (anterior inferior cerebellar arteries) supplies caudal/ lateral pons, and superior cerebellar arteries supply lateral/rostral pons and overlying cerebellum
basal artery also bifurcates to form posterior cerebral arteries that branch to supply both medial and lateral midbrain
what does the medial branch of the basilar artery (running length of pons) supply?
forms paramedian branches
supplies medial pons
what does the lateral branch of the basilar artery (running length of pons) supply? (hint: 2 branches here)
AICA (anterior inferior cerebellar arteries)- supply caudal/ lateral pons near CN VII (facial) and CN VIII (vestibulocochlear)
superior cerebellar arteries- supply rostral/lateral pons and overlying cerebellum
where do posterior cerebral arteries come from and what do they supply
basilar artery (runs length of pons) bifurcates into medial and lateral branches, lateral branch bifurcates to form pair of posterior cerebral arteries
these branch to supply both medial and lateral midbrain
a patient presents with a medial medullary vascular syndrome. in what artery branch is the blockage or insult likely to be?
anterior spinal artery branches- give rise to bilateral branches supplying medial medullary vascular territory
lateral brainstem medullary vascular syndromes are largely going to involve blockage of ____ that supplies lateral/ rostral medulla
PICA (posterior inferior cerebellar artery)- supplies lateral medulla
regardless of whether you are looking at the caudal or rostral pons, the ____ branches of basilar artery profuse medial pons vascular territory
paramedian branches of basilar artery
medial midbrain vascular insult is more common than lateral midbrain syndrome, and will involve these arterial branches
posterior cerebral artery- supply entire midbrain (medial and lateral, bifurcation of basilar artery)
a lesion of the corticospinal tract above the pyramidal decussation will result in (ipsilateral/contralateral) limb and trunk spastic weakness with hyperactive reflexes and Babinski sign
CONTRALATERAL
T/F: a medial midbrain vascular syndrome will result in injury to both the corticospinal tract and medial lemniscus
FALSE: at this point the medial lemniscus has already moved laterally
(this would be true if the lesion were in the medial medulla and pons)
most brainstem vascular syndromes are caused by a stroke involving branches of either the ____, _____, or _____
branches of vertebral arteries,
basilar artery,
or posterior cerebral artery
T/F: a lesion of the corticospinal, medial lemniscus, or spinothalamic tract in the brainstem will always have contralateral symptoms below the lesion
TRUE: either contralateral spastic weakness (corticospinal tract), loss of limb/trunk touch/vibration/proprioception (medial lemniscus), or loss of pain/temp (spinothalamic tract)
either tracts represent crossed axons going up or they are corticospinal tract axons that have not yet crossed because they are above pyramidal decussation
what CN can test to determine that a patient’s corticospinal tract has been lesioned in the medial midbrain? what about a lesion in the medial/caudal pons? what about medial medulla?
medial midbrain- CN III (oculomotor) and IV (trochlear) affected
media/caudal pons- CN VI (abducens) affected
medial medulla- CN XII (hypoglossal) affected
the signs from the CN will be IPSILATERAL
the signs of a brainstem tract lesion will be (contral/ipsilateral), but the signs of the associated CN lesion will be (contra/ipsilateral)
tract lesion- contralateral
CN lesion- ipsilateral
T/F: medial medullary vascular syndromes will have 2 crossed long tract signs
what will localize a lesion to this area (CN)?
TRUE: in medial medullary vascular territory both medial meniscus and corticospinal tract will be affected
hypoglossal nerve will localize this lesion (XII)
what does it mean to say a patient has “inferior alternating hemiplegia”?
spastic weakness of limbs on contralateral side, and tongue weakness/atrophy/deviation ipsilaterally
due to medial vascular injury in medulla (affects corticospinal tract, medial lemniscus, and hypoglossal nerve, XII)
what tracts will a lateral medullary vascular syndrome (Wallenberg’s syndrome) affect? what artery is occluded? what CN affected (3)?
lateral medullary syndrome- occlusion of either a vertebral artery or a posterior inferior cerebellar artery (PICA)
affects spinothalamic (pain/temp) and descending hypothalamic tracts (–> ipsilateral central Horner’s syndrome)
CN VIII (Vestibulocochlear, pons-medulla junction), IX (glossopharyngeal), X (vagus)
what kind of vascular injury does a patient with “dissociated loss of pain and temperature” have?
injury to lateral medullary vascular syndrome, by injury/ occlusion of posterior or inferior cerebellar artery or directly to branches of vertebral artery
loss of face/scalp pain/temp ipsilateral to lesion (due to injury to spinal nucleus of CN V–> Horner’s)
loss of pain/temp from contralateral limb/trunk (due to injury to spinothalamic tract)
how will a medial vascular injury to the medulla vs the caudal pons be different? (hint: think CN)
medial, so contralateral sign of injury to corticospinal tract
medulla- hypoglossal affected (XII)–> tongue weakness
pons- abducens affected (VI)–> internal strabismus (lack ability to abduct eye)
(both CN affected will show ipsilaterally)
contrast the differences in symptoms of a lateral medullary vascular syndrome and a lateral/caudal pontine vascular syndrome
long tracts are the same- spinothalamic and descending hypothalamic fibers
lateral medulla- PICA occlusion, CN VIII, IX, X
lateral pons- AICA, CN VII, VIII (vestibulocochlear, pons-medulla junction)
Weber’s syndrome, or medial midbrain vascular insult, is commonly caused by occlusion of ____
deep branches of posterior cerebral artery (branch of basilar artery)
a patient presents with ptosis, external strabismus, laterally deviated eye, loss of accommodation convergence reaction (near response) on one side, as well as spastic weakness on the other side of body. where is the vascular injury?
medial midbrain (Weber's syndrome) corticospinal tract (contralateral) and CN III (ipsilateral) affected
corticobulbar fibers also affected (run adjacent to corticospinal)- provide bilateral innervation to LMN in most cranial nerves (exception is LMN of facial nerve)
a patient presents with “superior alternating hemiplegia”, what does this mean?
medial midbrain vascular insult (Weber’s syndrome)
corticospinal tract, CN III, corticobulbar tract affected
spastic weakness contralateral, ocular motor deficits/ external strabismus ipsilateral
only lower face will be affected by corticobulbar lesion because it gives bilateral input everywhere except LMN of facial nerve going to lower half of face
Parinaud’s syndrome
compression of dorsal aspect of midbrain by pineal tumor, compresses:
- pretectal area–> bilateral pupillary reflex (Argyll Robertson pupils, or light-near dissociated pupils)
- superior colliculi (vision reflex)
- rostral interstitial nucleus- coordinating center for vertical gaze–> downward eye deviation, “setting-sun sign”
- cerebral aqueduct–> non-communicating hydrocephalus (high intracranial pressure)
patient presents with Argyll Robertson pupils, setting-sun sign, and non-communicating hydrocephalus. what do they have?
Parinaud’s syndrome- compression of dorsal midbrain by pineal tumor
Robertson pupils- light-near dissociated pupils, pupils do not constrict briskly to light reflex, but normally in accommodation conversion reflex (near response)
setting-sun sign- downward deviation of eyes (rostral interstitial nucleus affected, which coordinates conjugate vertical gaze)
non-communicating hydrocephalus- compression of aqueduct
Argyll Robertson pupils
light-near dissociated pupils
don’t constrict briskly to light reflex, but do constrict normally to near response
what is a symptom of compression or injury to the rostral interstitial nucleus, near the superior colliculi in the midbrain?
rostral interstitial nucleus- coordinates conjugate vertical gaze
“sun-setting sign”- downward deviation of eyes
pontocerebellar angle syndrome
acoustic or vestibular schwannoma- benign tumor in schwann cells of vestibulocochlear nerve (VIII) just outside of brainstem
tinnitius
ringing in ear
will patients with vestibular cochlear schwannoma have long tract symptoms?
NO- lesion is outside of brainstem
(tumor of schwann cells in CN VIII)
can affect other nearby cranial nerves
