10/11 Cranial Nerve Lesions

Question 1

• How do you tell the difference between an upper motor or lower motor neuron lesion?

Answer 1

o LMN—lesion is at the level of cranial nerve, symptoms tell if nerve or nucleus (more symptoms with nucleus)
o UMN—corticobulbar tract involved

Question 2

• Pattern of loss of pain and temperature information
Loss of pain and temperature sense ipsilateral to loss of touch and proprioception lesion has to be where the anterolateral system is anatomically close to medial DCML system.

Loss of pain and temp on one side and normal fine touch could be in spinal cord or caudal medulla below sensory decussation.

Loss of pain and temp on one side and contralateral face

Loss of function bilaterally

Answer 2

o Pattern narrows between brainstem, thalamus, and cortex. Entire body and face is likely rostral pons or midbrain
o If there is alteration of sensation of face, lower brain stem and lateral due to location of anterolateral system.
o lateral brain stem below level of CNV
o must be midline nuclei if brainstem related symptoms

Question 3

describe axon regeneration

Answer 3

o Axons in the periphery regenerate better than in CNS. After sectioning a peripheral nerve, the perineural sheath reforms and schwann cells in distal stump promote growth by producing trophic and attractant factors and adhesive proteins. After sectioning CNS axons, distal segment disintegrates and myelin fragments. Astrocytes and macrophages are attracted and form glial scar which inhibits regeneration

Question 4

• Peripheral cranial nerve lesions for CN II

Answer 4

o Blindness in eye on side of lesion

Question 5

• Peripheral cranial nerve lesions for CN III

Answer 5

o Eye is deviated abnormally—down and out/dilated pupil

Question 6

• Peripheral cranial nerve lesions for CN IV

Answer 6

o Eye is deviated slightly up and out and patients tilt head

Question 7

• Peripheral and clinical correlates of cranial nerve lesions for CN V

Answer 7

loss of all sensation on face on side of lesion over V1-V3. Cannot chew, no jaw jerk reflex. Hyperacusis (loss of tolerance to sounds).
o Ipsi paresis (chewing)—efferents from motor n. V
o Ipsi loss of touch on face—afferents to chief sensory n of V
o Ipsi loss of pain and temp from face—afferents to spinal n. V
o Hyperacusis—efferents from motor n. V to tensor tympani muscle of inner ear

Question 8

• Peripheral cranial nerve lesions for CN VI

Answer 8

o Eye is deviated medially due to CN III dominance.

Question 9

• Peripheral and clinical correlates of cranial nerve lesions for CN VII

Answer 9

o Loss of all facial expression on side of lesion. Loss of feeling in part of ear, tearing and salivation loss, some loss of taste anterior 2/3, hyperacusis.
o Paralysis of ipsilateral muscles of facial expression—efferents from motor n VII
o Loss of taste ant. 2/3 tongue. Afferents to n solitarius
o Hyperacucis (ipsilateral ear). Efferents from motor n of VII to stapedius muscle
o Diminished salivation. Efferents from salivatory n to submandibular and sublingual glands

Question 10

• Peripheral cranial nerve lesions for CN VIII

Answer 10

o Balance issues and deafness ipsi to lesion (vesibular)

Question 11

• Peripheral cranial nerve lesions for CN IX

Answer 11

o Difficulty swallowing. Efferents from n ambiguous to stylopharyngeus
o Loss of gag. Afferents from pharynx and posterior 1/3 of tongue to solitarius
o Loss of taste posterior 1/3. Afferents to n solitarius
o Loss of carotid sinus reflex. Afferents to solitarius (bp regulation)
o Diminished salivation. Efferents from salivatory n to parotid gland

Question 12

• Peripheral cranial nerve lesions for CN X

Answer 12

o Difficulty swallowing, some loss of gag, loss of some taste in epiglottis, loss of sensation in part of ear
o Difficulty swallowing. N ambiguous efferent to constrictors of pharynx, dysarthria
o Diminished gag. N ambiguous efferent to soft palate and uvula
o Loss of taste (epiglottis) afferents to n solitarius
o Loss of pain and temp from small area posterior ear. Afferents to spinal n of V
o Gut motility, heart rate problems.

Question 13

• Peripheral cranial nerve lesions for CN XI

Answer 13

o Neck and shoulder paralysis ipsi to lesion

Question 14

• Peripheral cranial nerve lesions for CN XII

Answer 14

o Tongue deviates ipsi

Question 15

• Which lesions result in eye movement problems?

Answer 15

o CN III, IV, and VI

Question 16

• Which lesions result in balance, eye, and hearing issues

Answer 16

o CN VIII

Question 17

• Which tracts are involved in clinical correlates of CN V lesions?

Answer 17

o Contralateral hemiplegia-corticospinal
o Contralateral lower face paralysis (upper face intact)—corticobulbar
o Loss of fine touch and proprioception—ML
o Loss of pain and temp left face—VTTT
o Loss of pain and temp left body—DCML

Question 18

• Describe how CN VII regulates facial expression

Answer 18

o two lower motor neurons synapse onto three upper motor neurons, one ipsilateral and two contralateral. Lesions in the umn on contralateral lead to facial weakness on lower face. Lesions to lmn affect entire side of face

Question 19

• Dorsolateral medullary lesions

Reduced salivation 
Reduced ipsi taste posterior 1/3
Loss of ipsi pain and temp 
Deaf in ipsi ear 
Vertigo 
Gait ataxia 
Reduced gag, swallowing, dysarthria 
Loss of taste epiglottis 
Gut motility, tachycardia

Answer 19

o	(CN IX/salivatory)
o	(solitary) 
o	(spinal V)
o	(CN VIII) 
o	(CNVIII + ICP) 
o.     (ICP) 
o	(CN IX, ambiguous) 
o	(CN IX/solitarius) 
o	(CN X fibers)