1.DDx Vertigo in descending order of commonality:

-BPPV

-Menieres

-Viral neuritis (recovers spontaneously in younger people, may takes months in older adults)

2. Menieres disease= idiopathic endolymphatic hydrops 

-Increased pressure in endolymph, stretching the membranes between perilymph and endolymph and causing nerve firing, leading to fluctuating vertigo, tinnitus, ear fullness. 

-"Attacks of hydrops probably are caused by an increase in endolymphatic pressure, which, in turn, causes a break in the membrane that separates the perilymph (potassium-poor extracellular fluid) from the endolymph (potassium-rich intracellular fluid). The resultant chemical mixture bathes the vestibular nerve receptors, leading to a depolarization blockade and transient loss of function. The sudden change in the rate of vestibular nerve firing creates an acute vestibular imbalance (ie, vertigo).

The physical distention caused by increased endolymphatic pressure also leads to a mechanical disturbance of the auditory and otolithic organs. Because the utricle and saccule are responsible for linear and translational motion detection (as opposed to angular and rotational acceleration), irritation of these organs may produce nonrotational vestibular symptoms.

This physical distention causes mechanical disturbance of the organ of Corti as well. Distortion of the basilar membrane and the inner and outer hair cells may cause hearing loss and/or tinnitus. Since the apex of the cochlea is wound much tighter than the base, the apex is more sensitive to pressure changes than the base. This explains why hydrops preferentially affects low frequencies (at the apex) as opposed to high frequencies (at the relatively wider base). Symptoms improve after the membrane is repaired as sodium and potassium concentrations revert to normal." (medscape)

3. Criteria for menieres:

-Vary from possible to likely to probable to definite to certain-- certain requires temporal bone autopsy. 

-"definitely" menieres:

-2 or more spontaneous episodes of vertigo lasting > 20 minutes (but less than say, 8 hours-- the idea is that the vertigo is not continuous) 

-Low frequency hearing loss (<1 kHz)

-Tinnitus or fullness in affected ear

-Other pathology ruled out 

4. Caloric reflex test: you put warm or cold water (at least 7 degrees different from body temp) into the ear, and you will see nystagmus (warm => endolymph in the ipsilateral horizontal canal rises => increased firing vestibular afferent nerve => mimics a head turn to the ipsilateral side => eyes drift towards contralateral side => bat-back horizontal nystagmus to the ipsilateral ear). This test will be hyporesponsive in menieres disease

5. Treatment (acute event): vestibular suppressants 

-Antihistamines: meclizine is nice as it is safe and has few drug-drug interactions. Causes sedation and dry mouth

-Phenothiazines: phenergan, compazine -- dystonia side effects

-Benzodiazepines are stronger vestibular suppressants than antihistamines are. Valium has been shown to be effective. In acute usage, it can speed up resolution of symptoms/compensation, however in a small % of people the symptoms will get worse. Start at low dose (2mg/day) and titrate up. Cons: 10% addiction rate. Vontrol is a powerful vestibular suppressant that will suppress all vertigo, but it causes hallucinations so it can only be given in a hospital setting. 

-Anticholinergics

-Non vestibular suppressants: antiemetics for symptomatic management. 

6. Maintenance/preventative treatment (conservative)

-Diuretics, to decrease theoretically fluid in inner ear, esp K sparing. 

-Low sodium diet (<1 g/day)

-No caffeine, tobacco, alcohol

7. Treatment (non-surgical)

-Injection of vestibulotoxins in ear, i.e. gentamycin. Gent hits vestibular system harder than auditory, but hits both; the incidence of hearing loss in affected ear is 3-10%. This is for those who have failed medical treatment (i.e. 15g/day of valium). 1-3 injections, for unilateral disease only. For those who get hearing loss, you can try steroids but theres no evidence they work

-Meniette device: applies pulses of low pressure to middle ear via PE tube. Treatment is 5 minutes TID. $$$$$. Discovered when people realized that airline travel resolved their symptoms. 

-Systemic vestibulotoxins for bilateral disease-- i.e. IM streptomycin. Streptomycin is much more vestibulotoxic than ototoxic, but it's both. Do not use dihydro-streptomycin, its really ototoxic. This paper from 1964 details the side effects of the drugs of the streptomycin family... it's strange to see kanamycin discussed as a drug to be used in people rather than a lab tool. Apparently its toxic to the cochlea. All of the streptomycin family of drugs (dihydro, kan, vanc, vio, neomycin, etc) are more ototoxic than vestibulotoxic except the original. 

-When you are using vestibulotoxins, titrate carefully-- if you completely destroy the vestibular system you will get oscillopsia. 

8. Treatment (surgical)

-Endolymphatic sac decompression shunt-- 66% effective 

-Cut vestibular nerve behind the labyrinth- 96% effective because in 4% of people, the 8th nerve goes to the cochlea before it goes to the labyrinth. To do this, you need a normal sigmoid sinus and well aerated mastoid. You can also cut the vestibular nerve in the brain, but you need to do a craniotomy via a retrosigmoid/posterior fossa approach. 

-Transcanal labyrinthectomy: drill out the canals, stuff cavity with gelfoam infused with gentamycin. 95% effective

-Total labyrinthectomy: you drill out the entire inner ear. If this is not effective, you have the wrong diagnosis. 

9. Facial nerve anatomic landmarks:

-First genu around geniculate

-Passes by stapedius bone 

-Exist stylomastoid foramen

-External bony landmark for finding trunk of facial nerve - tympanomastoid suture 

10. Superior canal dehiscence:

-Overlying temporal bone thins out. The membrane is intact, and leads intermittent vertigo (esp with pressure changes) and conductive hearing loss. 

-"Third window hypothesis": additional window in addition to round and oval window, so the conduction of signal through perilymph is less effective. 

-On the same hypothesis, you can treat otosclerosis with a foraminectomy (remove bone but leave membrane) to create a second window if you lose one.