see: [Rosen Cranial Nerve disorders](x-devonthink-item://7CFC3D01-37EB-4CA6-A1E0-847AC54CADD8?page=3) see also: [[Visual fields]], [[Diplopia]], [[Relative afferent pupillary defect|RAPD]], [[pupil exam]], [[Bell's Palsy]], [[Head trauma radiology#Brain Herniation types|Brain herniation]], [[pupil exam#pupil deviation|pupil deviation]] | CN | function | pathological features | causes | | ------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | II - optic | vision | unilateral vision loss<br>[[Relative afferent pupillary defect\|RAPD]] | - trauma<br>- tumor <br>- inflammatory (optic neuritis; [[Multiple Sclerosis\|MS]])<br>- ischaemic | | III - oculomotor | - extraoculomotor function LR6(SO4)3<br>- pupillary constriction | - ptosis (loss of levator palpebrae)<br>- down and out deviation<br>- [[Diplopia]]<br>- dilated, non-reactive pupil<br>- loss of accommodation | - trauma (herniation of temoral lobe through tentoral opening)<br>- ischaemic (*especially diabetes*)<br>- vascular - *PCA aneurysm*<br>- [[myasthena gravis]] | | IV - trochlear | motor superior oblique | - inability to move eye downwards and laterally<br>- pts tilt head towards unaffected eye to overcome inward rotation of affected eye | - trauma most common cause | | V - trigeminal | - motor muscles of mastication<br>- sensory to cornea, face, scalp, oral cavity | - partial facial anaesthesia<br>- eipsdic face pain | - facial bone fracture<br>- *infraorbital nerve* (branch of maxillary) associated with [[Facial trauma radiology#Orbital floor blowout fracture\|orbital floor blowout fracture]] | | VI - abducens | motor lateral rectus | - inability to move affected eye laterally<br>- diplopia attempting lateral gaze | - tumor<br>- elevated ICP<br>- cavernous sinus lesion | | VII - facial | - motor muscles of facial expression<br>- sensation to ear canal and tympanic membrane | - hemifacial paresis<br>- sensory deficit around ear<br>- intolerance to sudden loud noises | - lower motor neuron: entire side of face paralysed (eg [[Bell's Palsy]] or lyme disease), bacterial infection from [[Acute Otitis Media\|otitis media]]<br>- upper motor neuron - forehead musculatore functions still eg from [[Stroke]] or tumor<br>- pain and vesicles, likely [[Herpes zoster#Ramsey Hunt syndrome\|VZV → Ramsay Hunt Syndrome]] | | VIII - vestibulocochlear | hearing and balance | - unilateral hearing loss<br>- tinnitus<br>- [[vertigo]], unsteadiness | - tumor (acoustic neuroma). mimics meniere disease | | IX - glossopharyyngeal | - sensation posterior third of tongue<br>- taste posterior 1/3<br>- motor supply o stylopharyngeus | - rare in isolation | brainstem lesion<br>neuralgia of nerve | | X - vagus | - motor to muscles of parhynx, larynx<br>- motor to smooth muscles of parynx, larynx, thoracic, abdo viscera<br>- sensory from larynx, trachea, esophhagus, thoracic and abdo viscera | - unilateral loss of palate elevation ; drinking fluids, comes out nose<br>- unilateral vocal cord paralysis (horse voice) | - brainstem lesion<br>- injury to recurrent laryngeal nerve in surgery | | XI - spinal accessory | motor supply to SCM and trapezius | downward and lateral rotation of scapula and shoulder drop | trauma | | XII - hypoglossal | motor supply to intrinsic and extrinsic muscles of tongue | - tongue deviations | - UMN lesion from stroke or tumor causes tongue to deviate to opposite side<br>- LMN lesion causes tongue ot deviate to same side of lesion. bilat from ALS<br>- metastatic disease to skull base may involve the nerve | ![[Pasted image 20240308152354.png|muscle dysfunction, sx, and examination findings for each oculomotor cranial nerve palsy]] ![[Pasted image 20240308152535.png|cardinal movements of the eyes]] # CN III palsy CN III: - enters through superior orbital fissure - innervates extraoccular muscles other than lateral rectus and superior oblique LR6(SO4)3 - pupillary constriction and accomodation - eyelid raising > - motor features predominant in intrinsic disease (eg diabetic neuropathy) > - ptosis > - eye in "down and out" position > - inability to elevate, depress, or turn medially > - pupillary features predominant in extrinsic compression (eg raised ICP) > - [[mydriasis]] > - absent direct light reflex > - absent accommodation reflexes **causes** - extrinsic compression - *aneurysms* - ==a patient with sudden onset of painful third nerve palsy with pupil involvement== and no h/o trauma or vascular disease needs immediate ix for an intracranial aneurysm (most commonly PCA) until proven otherwise - tumours -- esp nasopharyngeal carcinoma - [[traumatic brain injury#Signs of raised intracranial pressure ( ICP )|Raised ICP]] -- eg from [[Head trauma radiology#Brain Herniation types|uncal herniation]] - intrinsic disease - diabetes - arteritis - [[Multiple Sclerosis]] - [[Guillain-Barré syndrome|GBS]] -- Miller Fischer syndrome - botulism - dipthernia - binocular horizontal, vertical, or oblique [[Diplopia]] - paralysis of adduction, elevation, and depression ; ==eye looks "down and out"== - ptosis - +/- pupil dilation - pupil constriction is mediated by parasympathetic fibres that accompany CN III; they travel peripherally and are more susceptible to compression, resulting in pupil dilation (from unopposed sympathetic supply) - therefore, in CN III palsy, presence or absence of ipsilateral pupil dilation helps distinguish btwn compressive aetiology (eg aneurysm) and microvascular/ischaemic aetiology **anisocoria** - unequal size of pupils **Locations of CN III lesions**: - brainstem/midbrain (eg around oculomotor nuclei) - dizziness, vertigo, ataxia, aphasia - contralateral cerebellar deficits or contralateral hemiparesis - intra-cranial course (eg along lateral wall of cevernous sinus) - involvement of other CN - 4, 5th, 6th - orbital (superior orbital fissure, orbital apex) - orbital signs - chemosis, conjunctival injection, proptosis, visual loss, 4th or 6th