12. Fluid systems of the labyrinth, Meniere’s disease, toxic lesions of the inner ear
- Fluid systems of the labyrinth
- Membranous labyrinth
- Filled with K-rich endolymph
- Contains hair cells
- Divided into vestibule and cochlear duct
- Bony labyrinth
- Contains membranous labyrinth in Na-rich perilymph
- Three cavities
- Scala media (cochlear duct)
- Filled with endolymph
- Basilar membrane forms the floor of it
- Scala vestibuli
- Filled with perilymph
- Above and separated from scala media
- Connected to scala tympani at helicotrema
- Scala tympani
- Filled with perilymph
- Below and separated from scala media
- Runs downward from helicotrema to the round window
- Scala media (cochlear duct)
- Oval window vibrates -> sound waves transmitted in perilymph in scala vestibuli
- -> sound waves vibrate the vestibular membrane and basilar membrane, thus stimulating hair cells
- -> sound waves travel through helicotrema -> down the scala tympani -> to the round window
- Low frequency waves act at apex of cochlea
- High frequency waves act at base of cochlea
- Membranous labyrinth
- Toxic lesions of the inner ear
- Etiology
- Endogenous
- Metabolic diseases
- Diabetes mellitus
- Uraemia
- Bacterial toxins
- Metabolic diseases
- Exogenous
- Aminoglycosides
- Loop diuretics
- Cytostatic drugs
- Salicylates
- Industrial solvents
- Heavy metals
- Alcohol
- Illegal drugs
- Endogenous
- Serous labyrinthitis
- Bacterial toxins from chronic otitis media
- Etiology
- Meniere disease (idiopathic endolymphatic hydrops)
- Impaired resorption of endolymph causes accumulation
- Epidemiology
- Females
- Older adults
- Clinical features
- Meniere triad
- Episodes lasting from minutes to hours
- 3 yes 1 no
- Yes: Sensorineural HL
- Yes: Repeated attacks of vertigo
- Yes: Tinnitus
- No: No neurological signs
- Meniere triad
- Diagnosis
- Criteria
- >1 episode that lasts 20 minutes to 12 hours
- Low-mid frequency SN hearing loss
- Tinnitus
- Criteria
- Treatment
- Avoid triggers (stress, alcohol, caffeine)
- Low sodium diet
- Rehabilitation
- Bed rest
- Drugs
- First generation antihistamines
- Histamine analogues
- Gentamycin in ear – destroy vestibule
- Surgery
- Labyrinthectomy
- Sacculotomy
- Vestibular neurectomy