CN 6

Question 1

CN 6 innervates… (2)

Answer 1

1. Ipsilateral LR muscle
2. Internuclear motor neurons

Question 2

T/F: Pts with a CN 6 Palsy will experience diplopia

Answer 2

Eh, not always

Question 3

Facial Colliculus Syndrome

Answer 3

Ipsilateral upper and lower facial weakness + horizontal gaze palsy

Question 4

Common cause of CN 6 fascicular lesion

Answer 4

Occlusion of branches of basilar artery

Question 5

Internuclear Opthalmoplegia

Answer 5

Contralateral gaze —> inability for ipsilateral eye to adduct and nystagmus of abducting eye

Question 6

CPA lesion will affect which CN’s

Answer 6

5, 6, 7, and 8

Question 7

Signs of CPA CN 6 Lesion

Answer 7

First sign: decreased corneal sensitivity

+ Cerebellar signs: ataxia, nystagmus, gait imbalance

Question 8

Foville Syndrome
1. Location of Lesion
2. Clinical Presentation

Answer 8

Location: Dorsal Pons

Clinical Presentation:
1. Ipsilateral CN 7 palsy (loss of taste on ant 2/3 of tongue)
2. Ipsilateral gaze palsy
3. Facial hypothesia
4. Possible: Ipsilateral Horner’s, INO, contralateral hemiparesis, and CN 8 palsy

Question 9

Raymond’s Syndrome
1. Location of Lesion
2. Clinical Presentation

Answer 9

Location: Ventral Pons

Presentation:
CN 6 palsy + contralateral hemiplegia (complete paralysis)

Question 10

Millard-Gubler Syndrome
1. Location of Lesion
2. Clinical Presentation

Answer 10

Location: Ventral Pons

Presentation:
CN 6 and 7 palsies + contralateral hemiplegia (complete paralysis)

Question 11

2 General Signs of CN 6 palsy

Answer 11

1. Ipsilateral head turn
2. Limitation of abduction (may be subtle)

Question 12

Most common isolated palsy?

Answer 12

CN 6!

Question 13

Why is horizontal diplopia worse at distance with CN 6 palsy?

Answer 13

Eyes diverge at distance

Question 14

Dorello’s Canal
1. Formed by…
2. Relevance to CN 6
3. Causes Unilateral or Bilateral defect?

Answer 14

1. Petroclinoid ligament
2. CN 6 runs through it (can be displaced by change in ICP)
3. Can be either

Question 15

Difference between Gradenigo’s vs Pseudo-Gradenigo’s

Answer 15

Gradenigo is an infection of the middle ear/mastoid air cells

Pseudo-Gradenigo is non-infectious

Question 16

Examples of Pseudo-Gradenigo etiology

Answer 16

1. Nasopharyngeal carcinoma
2. CPA Tumor
3. Trauma (e.g. petrous bone fracture)

Question 17

Ocular Management of CN 6 Palsy (4)

Answer 17

1. Fresnel Prism (BO)
2. Temporal (or full) occlusion
3. Botox injections to ipsilateral MR
4. Strab surgery (if stable 6-12 months)

Question 18

How does an aneurysm in ICA cause CN 6 defect?

Answer 18

Proximity in Cavernous Sinus

Question 19

Most common aquired causes of CN 6 palsy

Answer 19

Trauma and Neoplasms (< 50)

Vasculopathic (> 50)

Question 20

Most common congenital CN 6 palsy

Answer 20

Duane’s Retraction Syndrome

Question 21

CN 6 is primarily involved with which Type of Duane’s

Answer 21

Type 1 (Impaired Abduction)

Question 22

Is the pathophysiology of a CN 6 orbital apex lesion mechanical or neurological in nature?

Answer 22

Can be either

Question 23

Orbital signs of CN 6 lesion of orbital apex

Answer 23

(Honestly of any orbital apex lesion)

• Proptosis
• Chemosis
• Conj injection

Question 24

What is the cause of both Gradenigo and Pseudo-Gradenigo?

Answer 24

Localized inflammation of meninges at petrous apex

Question 25

Spasm of Near Reflex (3)

Answer 25

1. Accommodation spasm
2. Acute ET
3. Miosis

Question 26

Functional Spasm of Near Reflex

Answer 26

Anxiety and emotional distress

Question 27

Organic Spasm of Near Reflex

Answer 27

e.g. head trauma or neurological disease (MS, Arnold-Chiari, Tumors)

Question 28

RE of a near spasm patient

Answer 28

Pseuodomyopia w/ hyperopic shift after wet refraction

Question 29

Why is Spasms of Near Reflex a DDX for CN 6 palsy?

Answer 29

Acute ET presents w/ limitation of abduction

Question 30

Mandatory imaging, associated with/ CN 6 palsy (8)

Answer 30

1. 50+
2. No Hx of HTN/DM
3. Assumed Vasculopathic lesion that does not resolve in 3 months
4. Pain
5. Bilateral palsy
6. Papilledema
7. Hx of Cancer
8. Hx of Trauma