CH 13: Lesions of the BS Flashcards
CN nuclei mostly innervate structures on what side?
ipsilateral
what CN innervates the contralateral side?
CN 4- trochlear
a lesion of the ascending and descending pathways typically affects which side of the body?
contralateral (*after the motor and sensory decussations in the lower medulla)
a unilateral lesion of the BS often causes:
loss of function of CNs on the ipsilateral side
and
hemiplegia/hemisensory loss on the contralateral side
the rostrocaudal level of the lesion can be determined by :
the CNs affected
the mediolateral position of the disease process within the BS can be determined by:
the positions of the long tracts affected
in the medulla and pons the corticospinal tracts and ML remain:
in relatively consistent positions- close to the midline and base
unilateral medial lesions of the medulla and pons cause:
contralateral hemiparesis and loss of position and vibratory sensation (corticospinal and ML remain close to the midline and base at these levels)
Reticular formation includes autonomic components important in controlling:
respiration
blood pressure
GI functions
also functions in:
arousal
wakefulness
sleep
large BS lesions that affect RF bilaterally can cause:
coma or sudden death
leading causes:
ischemic or hemorrhagic strokes
severe craniocerebral trauma
what do BS lesions result from?
pathologic processes:
- hemorrhage
- vascular occlusion
- tumor
- multiple sclerosis
when a lesion occurs acutely (as with vascular occlusion) what are the symptoms?
initially LMN symptoms
within 4-8 weeks UMN symptoms
a lesion affecting the R hypoglossal nerve and the R pyramid results in:
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
a lesion affecting the R hypoglossal nerve and the R pyramid that extends to the L pyramid results in:
what artery supplies this area?
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
a lesion affecting both pyramids, the R hypoglossal nerve and extending dorsally would result in?
dorsal extension= extension into the R ML
contralateral loss of proprioception, tactile and vibration sense
what structures would be affected by a medial lesion of the medulla?
pyramids
ML
hypoglossal nerve
what structures would be affected by a lateral lesion of the medulla?
lateral spinothalamic tracts nucleus ambiguus (9,10,11-- SVE- pharynx, larynx)
a lateral lesion on the R open medulla would result in: (LSTT, ambiguous)
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
what is dysphonia?
hoarseness, weakness, or even loss of voice
what does the posterior inferior cerebellar artery supply?
what is it a branch of?
the dorsolateral portion of the medulla and the inferior surface of the cerebellar vermis
branch of the vertebral artery
dysfunction in the dorsolateral sector of the upper medulla usually results from:
what is the name of the syndrome?
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
damage in the dorsolateral medulla involves ___ and results in:
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
a medial basilar lesion of the caudal pons may include:
the corticospinal tract
emerging CN 6
what would a lesion including the R corticospinal tract and the emerging R abducens nerve result in?
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
a caudal pons lesions affecting the corticospinal tracts, and the emerging CNs of 6 and 7 is called ?
Millard-Gubler Syndrome
a medial pontine lesion with dorsal expansion into the pontine tegmentum involves ___ and results in ___?
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)
what is internuclear ophthalmoplegia?
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
what is the difference between bilateral and unilateral inter nuclear ophthalmoplegia?
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)
lesions of the dorsolateral caudal pons usually result from:
occlusion of the AICA
damage to the motor fibers of CN V leads to:
paralysis of the muscles of the ipsilateral jaw and causes the jaw to deviate to the same site with the opening of the mouth
damage to the sensory fibers of CN V causes:
anesthesia of the ipsilateral side of the face and mouth, with loss of the corneal reflex with the same eye is stimulated
what would a lesion of the basis of the upper midbrain involve? what are the results?
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
the combination of unilateral oculomotor palsy and contralateral hemiplegia is called? what usually causes it?
Weber’s Syndrome
vascular occlusion or an aneurysm of the basilar artery
a lesion of the tegmentum of the rostral midbrain affects:
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
what is locked in syndrome? what causes it?
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
bilateral lesions that damage substantial amounts of RF in the upper pons and midbrain leads to?
leads to coma- state of unresponsiveness
