Neuro VIII Flashcards
What happens with CN V motor lesion?
Jaw deviates TOWARD side of lesion due to unopposed opposite pterygoid
What happens with CN X lesion?
1) uvula deviates AWAY from side of lesion (SCM)
Weak side collapses and uvula points away
What happens with CN XII lesion?
Tongue deviates TOWARD side of lesion (“lick your wounds”) due to weakened tongue muscles on affected side.
What happens with facial nerve UMN lesion?
Contralateral paralysis of lower muscles of facial expression, sparing forehead due to bilateral UMN innervation
Presentation of facial nerve LMN lesion?
1) ipsilateral paralysis of upper and lower muscles of facial expression.
2) hyperacusis + loss of taste sensation to anterior tongue.
most common facial nerve palsy?
Idiopathic (aka Bell palsy)
other causes of facial nerve palsy?
1) lyme disease
2) HSV
3) herpes zoster (Ramsay hunt syndrome)
4) sarcoidosis
5) tumors
6) DM
path of venous drainage from eye and superficial cortex
eye and superficial cortex –> cavernous sinus –> internal jugular vein.
Cavernous sinus syndrome presentation
1) Variable ophthalmoplegia
2) decreased corneal sensation 3) Horner syndrome
4) occasional deceased maxillary sensation
CN most susceptible to injury with cavernous sinus syndrome
CN VI
Causes of cavernous sinus syndrome
1) mass effect from tumor
2) carotid-cavernous fistula
3) cavernous sinus thrombosis related to infection
tonotopy concept
Each frequency of vibration of hair cells leads to vibration at specific location on basilar membrane.
Where are frequencies heard in cochlea?
1) Low frequency heard at apex near helicotrema (wide and flexible).
2) High frequency heard base at base of cochlea (thin and rigid).
Rinne test findings with conductive hearing loss
Abnormal (bone greater than air)
Rinne test findings with sensorineural hearing loss
Normal (air greater than bone)
weber test results
Localizes to affected ear with conductive, and normal ear with sensorineural.
How do sudden extremely loud noises produce hearing loss?
Due to tympanic membrane rupture.
Where do cholesteatomas occur?
middle ear
What is a cholesteatoma?
overgrowth of desquamated keratin debris
Sequela of cholesteatoma?
Can erode ossicles and mastoid air cells causing conductive hearing loss.
Inner to outer layers of eye
Retina –> choroid –> sclera
what inhibits aqueous humor production?
1) beta blockers
2) A2 agonists
3) carbonic anhydrase inhibitors
Receptors on Iris dilator muscle?
alpha2
Receptors on iris sphincter muscle?
M3
Aqueous humor pathway
produced in ciliary body –> flows through posterior chamber up and over lens –> flows above iris –> then flows through trabecular meshwork and into canal of scheme and into episcleral vasculature (90% OR drains into urea and sclera (uveoscleral outflow)
With do M3 agonists affect?
trabecular outflow.
What do prostaglandin agonists affect?
Uveoscleral outflow
Hyperopia pathophys
Eye too short for refractive power of cornea and lens –> light focused behind retina.
Myopia pathophys
Eye too long for refractive power of cornea and lens –> light focused in front of retina.
astigmatism etiology and sequela
Abnormal curvature of cornea leading to different refractive power at different axes.