CN 6 Flashcards
CN 6 innervates… (2)
- Ipsilateral LR muscle
- Internuclear motor neurons
T/F: Pts with a CN 6 Palsy will experience diplopia
Eh, not always
Facial Colliculus Syndrome
Ipsilateral upper and lower facial weakness + horizontal gaze palsy
Common cause of CN 6 fascicular lesion
Occlusion of branches of basilar artery
Internuclear Opthalmoplegia
Contralateral gaze —> inability for ipsilateral eye to adduct and nystagmus of abducting eye
CPA lesion will affect which CN’s
5, 6, 7, and 8
Signs of CPA CN 6 Lesion
First sign: decreased corneal sensitivity
+ Cerebellar signs: ataxia, nystagmus, gait imbalance
Foville Syndrome
1. Location of Lesion
2. Clinical Presentation
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
Raymond’s Syndrome
1. Location of Lesion
2. Clinical Presentation
Location: Ventral Pons
Presentation:
CN 6 palsy + contralateral hemiplegia (complete paralysis)
Millard-Gubler Syndrome
1. Location of Lesion
2. Clinical Presentation
Location: Ventral Pons
Presentation:
CN 6 and 7 palsies + contralateral hemiplegia (complete paralysis)
2 General Signs of CN 6 palsy
- Ipsilateral head turn
- Limitation of abduction (may be subtle)
Most common isolated palsy?
CN 6!
Why is horizontal diplopia worse at distance with CN 6 palsy?
Eyes diverge at distance
Dorello’s Canal
1. Formed by…
2. Relevance to CN 6
3. Causes Unilateral or Bilateral defect?
- Petroclinoid ligament
- CN 6 runs through it (can be displaced by change in ICP)
- Can be either
Difference between Gradenigo’s vs Pseudo-Gradenigo’s
Gradenigo is an infection of the middle ear/mastoid air cells
Pseudo-Gradenigo is non-infectious
Examples of Pseudo-Gradenigo etiology
- Nasopharyngeal carcinoma
- CPA Tumor
- Trauma (e.g. petrous bone fracture)
Ocular Management of CN 6 Palsy (4)
- Fresnel Prism (BO)
- Temporal (or full) occlusion
- Botox injections to ipsilateral MR
- Strab surgery (if stable 6-12 months)
How does an aneurysm in ICA cause CN 6 defect?
Proximity in Cavernous Sinus
Most common aquired causes of CN 6 palsy
Trauma and Neoplasms (< 50)
Vasculopathic (> 50)
Most common congenital CN 6 palsy
Duane’s Retraction Syndrome
CN 6 is primarily involved with which Type of Duane’s
Type 1 (Impaired Abduction)
Is the pathophysiology of a CN 6 orbital apex lesion mechanical or neurological in nature?
Can be either
Orbital signs of CN 6 lesion of orbital apex
(Honestly of any orbital apex lesion)
- Proptosis
- Chemosis
- Conj injection
What is the cause of both Gradenigo and Pseudo-Gradenigo?
Localized inflammation of meninges at petrous apex
Spasm of Near Reflex (3)
- Accommodation spasm
- Acute ET
- Miosis
Functional Spasm of Near Reflex
Anxiety and emotional distress
Organic Spasm of Near Reflex
e.g. head trauma or neurological disease (MS, Arnold-Chiari, Tumors)
RE of a near spasm patient
Pseuodomyopia w/ hyperopic shift after wet refraction
Why is Spasms of Near Reflex a DDX for CN 6 palsy?
Acute ET presents w/ limitation of abduction
Mandatory imaging, associated with/ CN 6 palsy (8)
- 50+
- No Hx of HTN/DM
- Assumed Vasculopathic lesion that does not resolve in 3 months
- Pain
- Bilateral palsy
- Papilledema
- Hx of Cancer
- Hx of Trauma
