Vestibulaire implantatie en binnenoorpreservatie

Bilateral vestibular loss represents a major handicap with strong balance disturbances, higher risk of fall, visual symptoms (oscillopsia) and a loss of autonomy.

Prognosis is poor and treatment options are limited. At this moment, the department of ORL of Maastricht University Medical Center is working on a vestibular implant. Aim is to (partially) restore vestibular function.

However literature about hearing preservation during vestibular implantation is scarce. Until now, hearing preservation is only proven in a few animals. Humans who underwent implantation, were already deaf (our previous study) or lost hearing as a result of implantation (Washington group). The surgical technique and electrodes currently used, are not able to preserve hearing. Therefore surgical technique and electrode design must be improved in order to be able to implant people with (sub)normal hearing. This study investigates an improved surgical technique, together with a new electrode design and histopathological examination of implanted inner ears, aimed at preservation of hearing and vestibular function.

Ad 1. During surgery. After opening the bony semicircular canal (but leaving the membranous labyrinth inside the semicircular canal intact)

Ad 2. During surgery. After inserting an electrode inside the semicircular canal.

Ad 3. During surgery. After manipulation of the electrode inside the semicircular canal.

Ad 4. During surgery and after surgery. After opening the whole labyrinth with leakage of endolymph.

Ad 5. During surgery. After electrode placement (and before extensive electrode manipulation).

Ad 6. After surgery. Specimens of labyrinths are sent for histopathologic examination directly after surgery.

Routine labyrinthectomy with temporary electrode insertion

The surgeon will use the routine retro-auricular approach with mastoidectomy and exposition of the labyrinth, typical for destructive surgery of the labyrinth. Electrodes will be inserted into the labyrinth (specifically the semicircular canals) to evaluate insertion, manipulation and placement of the electrode design. Auditory function is evaluated through ABR and electrocochleography (ECochG) at every step of the surgery. After electrode manipulation inside the canals, the electrodes will be activated. Vestibular function in response to electrical stimulation will be measured. Afterwards the electrodes are taken out again.

The recordings will add at most 30 minutes to the destructive surgery. After the recordings, the whole labyrinth will be destructed as planned according to the initial surgery. Typically, the labyrinths would be disposed as medical waste, but here they will be fixed with paraformaldehyde and sent for histopathological examination.