Brain Stem and Vascular Lesions

Question 1

all sympathetic pathways are 3 neuron pathways. where are the 3 neurons?

Answer 1

1. first neuron of autonomic control always has cell body in hypothalamus- descend via descending hypothalamic axons
2. preganglionic sympathetic neurons at T1-T3- these leave thoracolumbar spinal cord
3. ascend up to superior cervical ganglia in sympathetic trunk

whole pathway is ipsilateral

Question 2

sympathetic pathways are ipsilateral/ contralateral? What about parasympathetic pathways?

Answer 2

sympathetic- ipsilateral

parasympathetic- bilateral

Question 3

the superior cervical ganglion provides all ____ input inside and outside of head

Answer 3

sympathetic innervation (3rd neuron in pathway)

Question 4

what are the 3 “-osis” of Horner’s syndrome?

Answer 4

ptosis (eye droop), miosis (constricted pupil), anhydrosis (loss of sweating)

(loss of sympathetic input to face)

Question 5

what lesion results in second order Horner’s syndrome?

Answer 5

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)

Question 6

a tumor presents with a tumor that results in third order Horner’s syndrome. what is being compressed?

Answer 6

superior cervical ganglion, 3rd neuron in 3 neuron pathway of sympathetic input

Question 7

a patient presents with Horner’s syndrome and contralateral loss of limb and trunk pain and temperature sensation. what happened?

Answer 7

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

Question 8

the corticobulbar track descends alongside what other tract in the ventral and medial position in the brain stem?

Answer 8

runs parallel to corticospinal tract

corticobulbar tract arises from motor cortex that controls cranial nerve motor neurons

Question 9

how does corticobulbar innervation differ from corticospinal innervation?

Answer 9

corticospinal crosses at pyramidal decussation and descends contralaterally
corticobulbar gives bilateral input to LMN

Question 10

what is different about corticospinal and corticobulbar tracts, functionally (what they’re innervating)?

Answer 10

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

Question 11

T/F: a lesion in the corticobulbar fibers coming from one side of motor cortex will not result in deficit

Answer 11

TRUE: corticobulbar fibers are bilateral, so you’ll still have other side

Question 12

the corticobulbar tract gives bilateral innervation except for:

Answer 12

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)

Question 13

how to tell the difference between a patient with a CN VII (facial nerve) lesion and lesion of corticobulbar tract?

Answer 13

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)

Question 14

what’s different about the two muscles that are innervated by CN XI (accessory, motor)?

Answer 14

trapezius receives contralateral input (same UMN innervation as all other upper limb LMN, via corticospinal tract)
sternocleidomastoid receives ipsilateral input (via corticobulbar innervation)

Question 15

entire brainstem and overlapping cerebellum is supplied (with blood) by medial and lateral branches of…..

Answer 15

vertebral basilar/ posterior circulation

Question 16

the origins of the vertebral basilar circulation come from pair of vertebral arteries arising from subclavian of lower neck, entering cranial cavity through the….

Answer 16

foramen magnum

Question 17

the ____ artery gives rise to bilateral branches that supply medial medullary vascular territory in brainstem

Answer 17

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

Question 18

what is the PICA artery and what does it supply blood to

Answer 18

posterior inferior cerebellar artery- supplies lateral medulla and posterolateral cerebellum

Question 19

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

Answer 19

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

Question 20

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?

Answer 20

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

Question 21

what does the medial branch of the basilar artery (running length of pons) supply?

Answer 21

forms paramedian branches

supplies medial pons

Question 22

what does the lateral branch of the basilar artery (running length of pons) supply? (hint: 2 branches here)

Answer 22

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

Question 23

where do posterior cerebral arteries come from and what do they supply

Answer 23

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

Question 24

a patient presents with a medial medullary vascular syndrome. in what artery branch is the blockage or insult likely to be?

Answer 24

anterior spinal artery branches- give rise to bilateral branches supplying medial medullary vascular territory

Question 25

lateral brainstem medullary vascular syndromes are largely going to involve blockage of ____ that supplies lateral/ rostral medulla

Answer 25

PICA (posterior inferior cerebellar artery)- supplies lateral medulla

Question 26

regardless of whether you are looking at the caudal or rostral pons, the ____ branches of basilar artery profuse medial pons vascular territory

Answer 26

paramedian branches of basilar artery

Question 27

medial midbrain vascular insult is more common than lateral midbrain syndrome, and will involve these arterial branches

Answer 27

posterior cerebral artery- supply entire midbrain (medial and lateral, bifurcation of basilar artery)

Question 28

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

Answer 28

CONTRALATERAL

Question 29

T/F: a medial midbrain vascular syndrome will result in injury to both the corticospinal tract and medial lemniscus

Answer 29

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)

Question 30

most brainstem vascular syndromes are caused by a stroke involving branches of either the ____, _____, or _____

Answer 30

branches of vertebral arteries, basilar artery, or posterior cerebral artery

Question 31

T/F: a lesion of the corticospinal, medial lemniscus, or spinothalamic tract in the brainstem will always have contralateral symptoms below the lesion

Answer 31

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

Question 32

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?

Answer 32

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

Question 33

the signs of a brainstem tract lesion will be (contral/ipsilateral), but the signs of the associated CN lesion will be (contra/ipsilateral)

Answer 33

tract lesion- contralateral | CN lesion- ipsilateral

Question 34

T/F: medial medullary vascular syndromes will have 2 crossed long tract signs what will localize a lesion to this area (CN)?

Answer 34

TRUE: in medial medullary vascular territory both medial meniscus and corticospinal tract will be affected hypoglossal nerve will localize this lesion (XII)

Question 35

what does it mean to say a patient has "inferior alternating hemiplegia"?

Answer 35

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)

Question 36

what tracts will a lateral medullary vascular syndrome (Wallenberg's syndrome) affect? what artery is occluded? what CN affected (3)?

Answer 36

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)

Question 37

what kind of vascular injury does a patient with "dissociated loss of pain and temperature" have?

Answer 37

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)

Question 38

how will a medial vascular injury to the medulla vs the caudal pons be different? (hint: think CN)

Answer 38

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)

Question 39

contrast the differences in symptoms of a lateral medullary vascular syndrome and a lateral/caudal pontine vascular syndrome

Answer 39

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)

Question 40

Weber's syndrome, or medial midbrain vascular insult, is commonly caused by occlusion of ____

Answer 40

deep branches of posterior cerebral artery (branch of basilar artery)

Question 41

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?

Answer 41

``` 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)

Question 42

a patient presents with "superior alternating hemiplegia", what does this mean?

Answer 42

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

Question 43

Parinaud's syndrome

Answer 43

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)

Question 44

patient presents with Argyll Robertson pupils, setting-sun sign, and non-communicating hydrocephalus. what do they have?

Answer 44

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

Question 45

Argyll Robertson pupils

Answer 45

light-near dissociated pupils | don't constrict briskly to light reflex, but do constrict normally to near response

Question 46

what is a symptom of compression or injury to the rostral interstitial nucleus, near the superior colliculi in the midbrain?

Answer 46

rostral interstitial nucleus- coordinates conjugate vertical gaze "sun-setting sign"- downward deviation of eyes

Question 47

pontocerebellar angle syndrome

Answer 47

acoustic or vestibular schwannoma- benign tumor in schwann cells of vestibulocochlear nerve (VIII) just outside of brainstem

Question 48

tinnitius

Answer 48

ringing in ear

Question 49

will patients with vestibular cochlear schwannoma have long tract symptoms?

Answer 49

NO- lesion is outside of brainstem (tumor of schwann cells in CN VIII) can affect other nearby cranial nerves