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CN III, IV, VI
CNpathies
| Question | Answer |
|---|---|
| 43 yo guy w/ L sided weakness/neglect. exam w/ mild R ptosis. eyes midposition. R pupil reduced in diameter compared to L. what muscle is involved? | Tarsal (Muller's muscle) |
| what are the extraocular muscles controlled by the oculomotor nerve? | superior rectus medial rectus inferior rectus inferior oblique levator palpebrae |
| what's the function of CN III? | extraocular muscles constricts pupil accomodates converges sympathetic innervation |
| what's the major function of the oculomotor nerve? | raises eyelid (major) tarsal (Muller's muscles) are a minor contributor |
| what's the pathway for CN III? | exits medial midbrain b/w midbrain and pons runs between SCA and PCA parallel to posterior communicating artery: through cavernous sinus exits through superior orbital fissure |
| what's the presentation of the classic 3rd nerve palsy? | eye is "down and out" dilated pupil paralysis of accomodation ptosis |
| what's the pathology name of CN III based on the location? | nuclear: Parinaud's syndrome fascicular lesions: Weber, Claude, Benedikt SAH lesions cavernous sinus lesions: Tolosa Hunt syndrome |
| where is the lesion in Parinaud's syndrome? | dorsal midbrain periaqueductal grey |
| what are the clinical features of Parinaud's syndrome? | supranuclear upgaze paralysis setting sun sign: conjugate downgaze convergence and eyelid retraction: Collier's sign |
| what causes Parinaud's syndrome? | pinealomas ms stroke hydrocephalus: VP shunt failure |
| where is weber's syndrome? | base of midbrain CN III cortical spinal tracts |
| what are the clinical features of weber's syndrome? | ipsilateral 3rd n palsy contralateral hemiplegia |
| where is claude syndrome? | CN III red nucleus brachium conjunctivum |
| what are the symptoms of claude syndrome? | ipsi 3rd n palsy contra ataxia contra tremor |
| where is benedikt? | CN III red nucleus cortical spinal tract |
| any tumor in subarachnoid space presses on what? | CN III: dilated, unresponsive pupil |
| what's the most common aneurysm to cause a CN III palsy? | posterior comm aneurysm |
| if pt has uncal herniation, what can you see? | hutchinson pupil pupillar dilatation w/ poor response to light, but preserved convergence ischemic lesions |
| what if you have a CN III lesion that is pupil sparing related to diabetes? | will resolve in 3-6 mos |
| if CN III, IV, and VI are affected, where are you? | cavernous sinus |
| how do cavernous sinus lesions present? | oculomotor paresis fixed and dilated pupil horner's syndrome b/c of postganglioninc sympathetic fibers wrapped around ICA V1, V2 numbness |
| if CN II-V2 involved, what is it? | orbital apex syndrome: cavernous syndrome w/ visual loss |
| how does tolosa hunt syndrome present? | episodic paralysis of CN 3, 4, 6 (not always together) episodic orbital pain |
| how do you dx tolosa hunt? | granuloma on MRI or bx ESR/CRP elevated CSF normal other causes excluded |
| tolosa hunt tx? | steroids |
| what does the superior oblique muscle do? | depresses, intorts and abudcts the eye |
| what's the only CN to exit dorsally? | CN IV |
| what's the path of CN IV? | nucleus at level of inferior colliculus exits midbrain dorsally & decussates runs along undersurface of tentorium along lateral wall of cavernous sinus enters orbit through superior orbital fissure slender and long (prone to injury) |
| what's the most common cause of CN IV injury? | head trauma |
| what dx should you think about in an adult w/ a new 4th n palsy? | decompensation of a congenital palsy as it's the most common cause of CN IV palsies in kids |
| what are the clinical features of CN IV? | vertical diplopia- worse w/ downgaze head tilting extorsion impairment of depression of adducted eye hypertropia (elevated eye) weakness of down gaze |
| w/ CN IV palsy, which way do you tilt head? where are symptoms worse? | tilt head away from palsy tilting head to the same side of the lesion makes it worse (Bielschowsky test) |
| what's the path of CN VI? | nucleus in lower dorsal pons emerges b/w pons & medulla lateral cavernous sinus exits out superior orbital fissure |
| what are the syndromes you can have w/ CN VI palsies? | mobius Duane's Millard-Gubler syndrome Foville syndrome |
| how does mobius syndrome present? | horizontal gaze disturbance facial diplegia |
| what other issues can mobius be associated w/? | limb abnorm chest wall abnorm crossed eyes corneal abrasions |
| how does Duane's syndrome present? | limitation of adduction retraction of eyeball into socket on adduction poor convergence face turns to affected side to compensate for ltd mvmnts |
| what's the pathology in Duane's syndrome? | aplasia of 1 or both CN VI nuclei lateral rectus palsy |
| what's the pathology in Mobius syndrome? | bilateral abducens palsies CN VII palsies |
| what other issues can be ass w/ Duane's? | ocular, ear and systemic malformations |
| how does Millard-Gubler syndrome present? | ipsi horizontal gaze palsy (VI) ipsi weak face (VII) contra hemiparesis (cortical spinal tracts) |
| how does Foville syndrome present? | ipsi horizontal gaze palsy (VI) ipsi weak face (VII) contra hemiparesis contra sensory loss INO |
| where is Millard-Gubler syndrome localized to? | CN VI and pons |
| what causes Foville syndrome? | AICA infarct |
| what's the anatomy of yoked eye movements? | internuclear neurons exit the abduscens nucleus cross midline and arise in MLF terminate in MR nucleus |
| what are the clinical features of Internuclear ophthalmoplegia? | inability to adduct one eye w/ contralateral nystagmus adduction w/ convergence movements are intact |
| what are common causes of INO? | MS vascular d/o head trauma |
| how does one and a half syndrome present? | conjugate horizontal gaze palsy in one direction INO in the other direction |
| what causes one and a half syndrome? | PPRF lesion lesion in ipsi MLF |
Created by:
Syndenham
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