High in males (40-60 years old)
Clinical Manifestations: * fluctuating, progressive sensorineural hearing loss * tinnitus or a roaring sound * feeling of pressure or fullness in the ear * episodic, incapaciating vertigo (severe dizziness) * nausea and vomiting
The endolymph and perilymph (ie, fluids that fill the chambers of the inner ear) are separated by thin membranes that house the neural apparatus of hearing and balance. Fluctuations in pressure stress these nerve-rich membranes, causing hearing disturbance, tinnitus, vertigo, imbalance, and a pressure sensation in the ear.
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