49. CN/Brain Lesions

Question 1

How are the functional components of CNs organized on the brainstem?

Answer 1

Lateral to Medial:
Special Sensory
Somatic Sensory
Visceral Sensory
Autonomic
Branchiomotor
Motor

Question 2

Describe the path of all sensory CN nuclei:
What order neurons have cell bodies in the nuclei?

Where do lesions cause contralateral and ipsilateral deficits?

Answer 2

1o: cell bodies in sensory ganglia of CN - processes enter brainstem and synapse to CN nuclei
2o: CN nuclei - decussate and go to thalamus
3o: thalamic nuclei - post central gyrus

Lesion of 1o neuron/sensory nuclei = IPSI loss
Lesion of 2o neuron/central pathway = CONTRA loss

Question 3

Describe the path of all motor nuclei? What neurons are in motor nuclei? Where do lesions cause ipsilateral and contralateral deficits?

Answer 3

Motor nuclei: cell bodies of LMN - leave brainstem via CN to muscles
UMN: corticobulbar tract from cortex to synapse bilaterally to BOTH motor nuclei (except lower face are only crossed)

Lesion of LMN: ipsilateral facial loss
Lesion of UMN: only contralateral lower facial loss

Question 4

Where are all somatic motor, parasympathetic, and branchiomotor nuclei located?

Answer 4

MEDIAL BRAINSTEM
Somatic motor:
CN3 - oculomotor nucleus = sup col of midbrain
CN4 - trochlear nucleus = inf col of midbrain
CN6 - abducens nucleus = pons
CN12 - hypoglossal nucleus = hypoglossal trigone of medulla

Parasympathetic:
CN3 - Edinger-Westphal nucleus = sup col of midbrain
CN7 - sup salivary nucleus = pontomedullary junction
CN9 - inf salivary nucleus = pontomedullary junction
CN10 - dorsal motor nucleus = vagal trigone of medulla

Branchiomotor:
CN5: trigeminal motor nucleus = rostral pons
CN7: facial motor nucleus = caudal pons
CN9/10: nucleus ambiguus - medulla
CN11: accessory nucleus - SC

Question 5

Where are all visceral sensory, special sensory, and somatic sensory nuclei located?

Answer 5

LATERAL BRAINSTEM
Visceral Sensory:
Taste (CN7,9,10): rostral solitary or gustatory nucleus/tract in medulla
CN9,10: caudal solitary nucleus/tract in medulla

Special Sensory:
CN8: vestibular and cochlear nuclei in rostral medulla/caudal pons

Somatic Sensory:
CN5: mesencephalic (midbrian), main/principal/chief (pons), spinal nucleus/tract (medulla)

Question 6

What are the characteristics of a hemisphere (supranuclear lesion)?
Sensory deficit? Motor Deficit? Tongue and Uvula deviation?

Answer 6

Supranuclear = CONTRALATERAL sensory and motor deficits in head AND body
Tongue: deviates away from lesion side
Uvula: deviates toward lesion side

Question 7

What are the characteristics of brainstem lesions in head and body?

Answer 7

Alternating Syndromes: Contralateral body deficits and Ipsilateral CN deficits

Question 8

Medial Medullary Syndrome

• cause
• deficits

Answer 8

Cause: occlusion of branch of vertebral arteries or anterior spinal arteries
ALTERNATING HYPOGLOSSAL HEMIPLEGIA
-contralateral hemiparesis (CS tract) and kinesthetic defects (Dorsal Column)
-ipsilateral flaccid tongue paralysis (dysarthria, dysphagia): tongue deviates toward lesion side

Question 9

Lateral Medullary Syndrome

• cause
• deficits

Answer 9

cause: occlusion of PICA
deficits: ALTERNATING HEMIANESTHESIA
- contralateral body hemianesthesia (damage to dorsal column)
- ipsilateral pain/temp loss of face (spinal nucleus)
- ipsilateral Horner’s Syndrome (autonomic damage - pupil constriction, ptosis)
- nystagmus, nausea, vomiting (special sensory - vestibular nuclei)
- ipsilateral vocal cord paralysis/loss of gag reflex (dysphagia, dysphonia, dyspnea) - loss of nucleus ambiguus - vagus branchiomotor

Question 10

Ventral (Weber’s) Syndrome of Midbrain

• cause
• deficits

Answer 10

Cause: occlusion of branch of PCA
ALTERNATING OCULOMOTOR HEMIPLEGIA
-contralateral hemiparesis (CS tract)
-ipsilateral CN3 palsy (diplopia, lateral strabismus - eye down and out, ptosis/mydriasis (dilation))