CN Palsies Part II

Question 1

Where do abducens nerve nucleus originate from? where do they exit?

Answer 1

1. pons
2. at junction of pons and medulla; ascends along cluivus of occipital bone and enters orbit via superior orbital fissure through annulus of zinn

Question 2

CN VI is _____ to the floor of the fourth ventricle and is closely related to PPRF. The fasciculus of CN ___ curves around nucleus.

Answer 2

ventral

Question 3

Nuclear lesions of CN VI will cause:

Answer 3

1. ipsilateral LR palsy
2. ipsilateral gaze deficits (bc affects PPRF too
3. ipsilateral CN VII palsy

Question 4

What does a fascicular lesion of CN VI cause?

Answer 4

1. ipsilateral facial numbness ( near CN V)
2. ipsilateral CN VII palsy
3. Descending sympathetic fibers: ipsilateral Horners
4. cerebral peduncles: contraleral hemiplegia
   5: vestibular nuclei: nystagmus

Question 5

what are causes of fascicular CN VII lesions

Answer 5

1. stroke (older patients)
2. MS (younger patients)
3. Tumor (kids)

Question 6

_______ angle and ___ lesions are due to subarachnoid CN VI palsy

Answer 6

cerebellopontine; clivus

Question 7

CN VI, VII, and VIII as well as ataxia is involved in ________ angle, due to acoustic neuroma

Answer 7

cerebellopontine

Question 8

Neoplasms (like meningioma), meningitis, and bilateral CN VI palsy is due to ____ lesions

Answer 8

clivus

Question 9

Since CN VI travels through the ____ of the the cavernous sinus, adjacent to the ICA, a cavernous sinus CN VI palsy may involve which nerves/fibers? What is this caused by?

Answer 9

body; CN III, IV, V1, V1, and sympathetic fibers (Horner’s)

• inflammation
• mass effect
• infection

Question 10

What is due to acquired isolated CN VI palsy in children?

Answer 10

1. trauma
2. neoplasm (brainstem glioma)
3. infection
4. inflammation

Question 11

What is due to acquired CN VI Palsy in young adults?

Answer 11

1. trauma
2. idiopathic
3. infectious
4. demylinating
5. Elevated ICP

Question 12

What is due to acquired CN VI palsy in older adults?

Answer 12

1. Ischemia
2. Neoplasm
3. Infection
4. Elevated ICP

Question 13

Any neurologic events in young adults make you think ____ lesions

Answer 13

demylinating

Question 14

A CN VI palsy results in ____ diplopia, and its at ____

Answer 14

horizontal; distance

Question 15

How do you manage isolated CN VI in children

Answer 15

1. obtain neurologic consultation
2. Monitor every 2-6 weeks for progression
3. MRI if no improvement in 3 months

Question 16

How do you manage isolated CN VI palsy in young adults

Answer 16

1. MRI
2. Blood work
   - Lyme
   - Symphilis
   - Collagen vascular disease
   - MS

Question 17

How do you manage isolated CN VI palsy in older adults

Answer 17

1. Rule out cardiovascular disease
2. ESR and CRP to rule out GCA (very elevated ESR rate)
   - normal value for men: half their age
   - normal value for women: half their age + 10
3. MRI if no resolution within 3 months

Question 18

anything ischemic should resolve within ____ months

Answer 18

3

Question 19

How do you rule out brainstem and cerebellopontine angle signs

Answer 19

1. contralateral hemiparesis: nicking cerebral peduncles
2. Horners: nicking descending sympathetic tract
3. facial palsy: nicking CN VII fascicles around nucleus
4. Facial analgesia: trigeminal nerve - also in pons
5. hearing loss (lesion in cerebellar pontine angle)
6. ataxia: cerebellum
7. nystagmus: cerebellum
8. rule out bilaterality and/or papilledema: clivus lesion
9. rule out facial pain:
10. rule out cavernous sinus syndrome:

Question 20

______ retraction syndrome is another cause of CN VI palsy which is a CONGENITAL disorder causing:

Answer 20

Duane’s’; agenesis of CN VI nucleus and nerve

-lateral rectus becomes innervated by CN III.

Question 21

What are features of CN VI palsy

Answer 21

1. patients are asymptomatic (learn to compensate for it)
2. globe retraction and narrowing of palpebral fissure on adduction
3. head turn toward the side with the deficit

Question 22

Describe Duane’s Syndrome Type 1

Answer 22

1. abduction impaired
2. adduction normal or slightly defective
3. most patients are orthophoric in primary gaze

Question 23

Describe Duane’s syndrome Type 2

Answer 23

1. Abduction normal

2. Adduction impaired due to improper contraction of LR on adduction

Question 24

Describe Duane’s syndrome Type 3

Answer 24

1. impaired adduction and abduction.

2. absent VI nuclei

Question 25

Other causes of CN VI palsy include _____ disease, the MR becomes inflamed, which causes mechanical restriction out. _____ also can cause CN VI palsy, as well as spasm of the near reflex (pseudo CN VI palsy)

Answer 25

Graves; MG

Question 26

multiple nerve palsies include: ____ ____ syndrome or ____ ___ syndrome.

Answer 26

cavernous sinus; orbital apex

Question 27

orbital apex syndrome includes CN:

Answer 27

II, IV, VI, and V1

Question 28

what are signs of carotid cavernous fistula

Answer 28

1. swelling 2. engorgement of vessels 3. injection

Question 29

_____ syndrome is actually a mechanical problem, not an IO palsy. It is caused by the ____ being stuck in the pulley. It will have a positive forced duction test and normal alignment in primary gaze. Features include an audible pop on attempted up gaze, usually congenital, but may be caused by trauma, inflammation or infection

Answer 29

Brown; SO; restriction of elevation in adduction , normal elevation in abduction.

Question 30

ischemic CN III palsy is usually 60+, and have to have at least one ____ risk factor. NO history of cancer, vasculitis, or autoimmune disease. COMPLETE CN III palsy (eye must be down and out) with _____ sparing. There should not be additional symptoms such as pain, weakness or numbness. There should not be any orbital signs. Spontaneous recovery by ____ months

Answer 30

vasculopathic (HTN, DM, smoking) pupil 3

Question 31

______ CN IV palsy can affect any age group, medical history is usually unremarkable. Diplopia make develop suddenly or gradually. Its usually compensated in younger patients. There will be evidence of longstanding ____ tilt. Vertical fusional amplitude > ____ degrees and less than 10 degree torsion on double Maddox rod test.

Answer 31

Congenital; head; 8

Question 32

Diabetic opthalmoplegia is usually ____ cranial nerve, but could be III or IV. Caveats are if pupil are involved then its compressive, not ischemic. Multiple simultaneous cranial nerve palsies means it is NOT ______. Pt must be in 40s or older and NO signs of _____

Answer 32

6th; microvascular; GCA --> superficial temporal artery; systemic inflammatory condition, ischemia because the lumen is now very small.

Question 33

what are brainstem signs of a CN Palsy

Answer 33

1. nystagmus 2. vertical gaze is limited 3. ipsilateral horners 4. contralateral hemiplegia

Question 34

what are cavernous signs of a CN palsy

Answer 34

1. multiple CN's are involved 2. horner's 3. decreased facial sensation

Question 35

what are orbital signs of a CN palsy

Answer 35

1. multiple CN's are involved 2. proptosis 3. positive forced duction test

Question 36

what would be considered an emergent workup

Answer 36

1. compressive: MRI 2. inflammatory: ESR to tell you how much inflammation is in body, CRP, platelets, temporal artery biopsy (want to rule out GCA)

Question 37

what would be considered urgent workup

Answer 37

1. Bloodwork (high yield) - Hgb A1c - Electrolytes - CBC, ESR, CRP - Acetylcholine receptor antibodies - Antibody to MuSK 2. Bloodwork (low yield) - ANA - RF - Cholesterol - Clotting factors