10Ménière's & cochlear otosclerosis
The remaining adult causes worth singling out are two diseases that each carry a particular complication for the implant team. Ménière's disease — the syndrome of endolymphatic hydrops — produces a fluctuating, low-frequency loss bound up with episodic vertigo, which makes candidacy assessment unusually tricky even though the spiral ganglion is generally well preserved. Cochlear otosclerosis turns the normally inert bone of the otic capsule into an active disease that can progress to profound 'far-advanced' loss and, at the operating table, conducts stimulating current to the facial nerve. Neither is common as an implant indication, but each illustrates how a cause can complicate not just the prognosis but the fitting and the surgery.
TTwo adult causes with a twist
Most adult sensorineural loss is presbycusis, noise or ototoxicity. Two further causes deserve their own module not because of their frequency but because of the practical wrinkles they bring to implantation — one in assessment, one in surgery.
CMénière's disease
Ménière's disease is attributed to endolymphatic hydrops — a distension of the endolymphatic compartment — and presents with the classic tetrad of episodic vertigo, fluctuating low-frequency hearing loss, tinnitus and aural fullness. The fluctuation is the problem for us: it complicates hearing-aid fitting and makes the timing of candidacy decisions harder, because the audiogram is a moving baseline. When the disease finally burns out into a fixed severe-to-profound loss, however, the spiral ganglion is usually well preserved, and implantation performs well.
CCochlear otosclerosis
Otosclerosis is abnormal remodelling of the otic-capsule bone. In its familiar form it fixes the stapes and causes a conductive loss treated by stapes surgery; but when the disease extends around the cochlea (retrofenestral or cochlear otosclerosis) it adds a sensorineural component and can progress to far-advanced otosclerosis with profound loss — an implant indication. Two surgical consequences follow from the abnormal bone: it can conduct current to the facial nerve, producing troublesome facial-nerve stimulation that complicates programming, and its demineralised “otospongiotic” phase can give a confusing CT picture and a more difficult cochleostomy.[2010]
CThe lesson they share
Ménière's and otosclerosis reinforce the chapter's wider point from a new angle: a cause can shape implantation not only through the substrate but through the process — the difficulty of assessing a fluctuating ear, or the hazard of a bony cochlea that talks to the facial nerve. Knowing the diagnosis lets the team anticipate both.
What explains the facial stimulation, and how is it managed?
Why does Ménière's disease complicate cochlear-implant candidacy assessment, and what is the silver lining?
What surgical complication is cochlear otosclerosis particularly associated with?