CH 13: Lesions of the BS

Question 1

CN nuclei mostly innervate structures on what side?

Answer 1

ipsilateral

Question 2

what CN innervates the contralateral side?

Answer 2

CN 4- trochlear

Question 3

a lesion of the ascending and descending pathways typically affects which side of the body?

Answer 3

contralateral (*after the motor and sensory decussations in the lower medulla)

Question 4

a unilateral lesion of the BS often causes:

Answer 4

loss of function of CNs on the ipsilateral side

and

hemiplegia/hemisensory loss on the contralateral side

Question 5

the rostrocaudal level of the lesion can be determined by :

Answer 5

the CNs affected

Question 6

the mediolateral position of the disease process within the BS can be determined by:

Answer 6

the positions of the long tracts affected

Question 7

in the medulla and pons the corticospinal tracts and ML remain:

Answer 7

in relatively consistent positions- close to the midline and base

Question 8

unilateral medial lesions of the medulla and pons cause:

Answer 8

contralateral hemiparesis and loss of position and vibratory sensation (corticospinal and ML remain close to the midline and base at these levels)

Question 9

Reticular formation includes autonomic components important in controlling:

Answer 9

respiration
blood pressure
GI functions

also functions in:
arousal
wakefulness
sleep

Question 10

large BS lesions that affect RF bilaterally can cause:

Answer 10

coma or sudden death

leading causes:
ischemic or hemorrhagic strokes
severe craniocerebral trauma

Question 11

what do BS lesions result from?

Answer 11

pathologic processes:

• hemorrhage
• vascular occlusion
• tumor
• multiple sclerosis

Question 12

when a lesion occurs acutely (as with vascular occlusion) what are the symptoms?

Answer 12

initially LMN symptoms

within 4-8 weeks UMN symptoms

Question 13

a lesion affecting the R hypoglossal nerve and the R pyramid results in:

Answer 13

the paralysis of the the L body

and

paralysis of the muscles on the R half of the tongue – tongue deviates to the R when protruded and the muscles progressively atrophy

Question 14

a lesion affecting the R hypoglossal nerve and the R pyramid that extends to the L pyramid results in:

what artery supplies this area?

Answer 14

causes R hemiplegia

in some patients, disease of the anterior spinal artery, results in recurring symptoms with recovery of function between attacks

if the original lesion and this lesion occur temporarily at different times, the result will be alternating hemiplegia – also occurs with ischemia of the basal part of the pons

Question 15

a lesion affecting both pyramids, the R hypoglossal nerve and extending dorsally would result in?

Answer 15

dorsal extension= extension into the R ML

contralateral loss of proprioception, tactile and vibration sense

Question 16

what structures would be affected by a medial lesion of the medulla?

Answer 16

pyramids
ML
hypoglossal nerve

Question 17

what structures would be affected by a lateral lesion of the medulla?

Answer 17

lateral spinothalamic tracts
nucleus ambiguus (9,10,11-- SVE- pharynx, larynx)

Question 18

a lateral lesion on the R open medulla would result in: (LSTT, ambiguous)

Answer 18

LSTT:
contralateral loss of P&T, sensation of the body

nucleus ambiguus:

• paralyzes voluntary muscles in the pharynx, larynx supplied by 9,10,11
• failure of R soft palate to contract causes difficulty swallowing (dysphagia) and on phonation the palate and uvula become drawn to the non paralyzed L side
• loss of R vocal cord function- dysphonia with hoarseness of voice

Question 19

what is dysphonia?

Answer 19

hoarseness, weakness, or even loss of voice

Question 20

what does the posterior inferior cerebellar artery supply?

what is it a branch of?

Answer 20

the dorsolateral portion of the medulla and the inferior surface of the cerebellar vermis

branch of the vertebral artery

Question 21

dysfunction in the dorsolateral sector of the upper medulla usually results from:

what is the name of the syndrome?

Answer 21

occlusion of the cerebral artery leading to thrombosis of the small penetrating branches or the PICA= Wallenberg’s syndrome

medullary injury from occlusion of the penetrating branches can occur without cerebellar involvement, OR cerebellar injury from occlusion of the PICA can occur without medullary involvement

Question 22

damage in the dorsolateral medulla involves ___ and results in:

Answer 22

inferior cerebellar peduncle:
-loss of spinocerebellar fibers–> ipsilateral cerebellar ataxia and hypotonia

spinal tract and nucleus of V

• loss of ipsilat P&T of the face
• loss of blink reflex after ipsilateral corneal stimulation

spinothalamic tract
-loss of contralateral P&T of body

nucleus ambiguus

• paralyzes voluntary muscles in the pharynx, larynx supplied by 9,10,11
• failure of R soft palate to contract causes difficulty swallowing (dysphagia) and on phonation the palate and uvula become drawn to the non paralyzed L side
• loss of R vocal cord function- dysphonia with hoarseness of voice

descending sympathetic pathways
-ipsilateral Horner’s syndrome: pupillary constriction, ptosis (partial upper lid closure), loss of ipsilat sweating of the face

emerging fibers of the vagus nerve -GVE
thoracic and abdominal viscera- bilateral innervation so won’t see much loss

vestibular nucleus
-nystagmus

Question 23

a medial basilar lesion of the caudal pons may include:

Answer 23

the corticospinal tract

emerging CN 6

Question 24

what would a lesion including the R corticospinal tract and the emerging R abducens nerve result in?

Answer 24

ipsilateral abducens palsy AND contralateral hemiplegia

abducens palsy= internal deviation of the R eye from paralysis of the R lateral rectus and the unopposed pull of the medial rectus muscle

immediately after the lesion, the hemiplegic limbs become hypotonic, hypo-reflexia
Chonically- hypertonic, spasticity, hyperreflexia

Question 25

a caudal pons lesions affecting the corticospinal tracts, and the emerging CNs of 6 and 7 is called ?

Answer 25

Millard-Gubler Syndrome

Question 26

a medial pontine lesion with dorsal expansion into the pontine tegmentum involves ___ and results in ___?

Answer 26

ML
-loss of position, vibration & tactile sensation on the contralateral side

paramedian pontine RF
-damage to neurons responsible for conjugate lateral gaze (R RF abolishes the ability to turn eyes voluntarily to the R and results in paralysis of R lateral gaze)

MLF
-damage produces “INTERNUCLEAR OPHTHALMAOPLEGIA”(commonly found in MS)

Question 27

what is internuclear ophthalmoplegia?

Answer 27

damage to MLF

commonly found in MS

with attempted gaze to one side, the adducting eye fails to move beyond midline but abducting eye moves fully outward by develops coarse nystagmus
gaze to the opposite side evokes the same

convergence often remains intact

Question 28

what is the difference between bilateral and unilateral inter nuclear ophthalmoplegia?

Answer 28

bilateral:
- caused by bilateral damage to MLF
- eye can’t adduct

unilateral:
-caused by unilateral damage to MLF
-occurs with vascular disease of the BS 
-eye can't adduct on conjugate movement
can adduct with convergence (demonstrating that loss of adduction results from a supra nuclear abnormality (an abnormality of UMN nuclei)

Question 29

lesions of the dorsolateral caudal pons usually result from:

Answer 29

occlusion of the AICA

Question 30

damage to the motor fibers of CN V leads to:

Answer 30

paralysis of the muscles of the ipsilateral jaw and causes the jaw to deviate to the same site with the opening of the mouth

Question 31

damage to the sensory fibers of CN V causes:

Answer 31

anesthesia of the ipsilateral side of the face and mouth, with loss of the corneal reflex with the same eye is stimulated

Question 32

what would a lesion of the basis of the upper midbrain involve? what are the results?

Answer 32

crus cerebri– corticospinal/bulbar tracts
-contralateral hemiplegia including the face

emerging CN 3

• external strabismus
• ptosis
• can’t raise upper eyelid
• pupil dilation
• loss of adduction beyond midline

Question 33

the combination of unilateral oculomotor palsy and contralateral hemiplegia is called? what usually causes it?

Answer 33

Weber’s Syndrome

vascular occlusion or an aneurysm of the basilar artery

Question 34

a lesion of the tegmentum of the rostral midbrain affects:

Answer 34

oculomotor nerve
-loss of function; paralysis of movement

ML (combined with VTTT)
-loss of tactile, position, vibration, P&T

Red nucleus and Superior cerebellar peduncle
-produces ataxia and involuntary movements of contralateral arm and leg

Question 35

what is locked in syndrome? what causes it?

Answer 35

bilateral lesions of the ventral pons, usually caused by occlusion of the basilar artery, can completely interrupt the corticobulbar and corticospinal tracts.

as a result, the patient becomes totally paralyzed and unable to speak but remains fully awake. usually, can open eyelids and can make slight vertical eye movements. (sparing of the dorsal parts of the midbrain)

communication can be established by asking the patient to move the eyes in response to a command. this establishes that the patient is completely immobile or “locked in” but is not in a coma

Question 36

bilateral lesions that damage substantial amounts of RF in the upper pons and midbrain leads to?

Answer 36

leads to coma- state of unresponsiveness