Taste Disorders in Middle Ear Disease and After Middle Ear Surgery

Taste sensations are provided by three different nerves of which the chorda tympani nerve (CTN) is the major taste nerve. It innervates taste buds in the two anterior thirds of the tongue. The CTN location in the middle ear predisposes for trauma of the nerve. In various forms of middle ear pathology, such as chronic otitis and cholesteatoma the nerve can be affected by the pathologic process per se, since the nerve may become exposed to bacteria toxins, enzymes or mechanical damage. During middle ear surgery, it can be cut off, stretched, touched or dried out by the heat of the microscope light beam. The nerve function in these situations is not clarified. Is it for example better to cut the nerve than to leave it traumatized after surgery. Therefore previous reports on objective CTN function pre- and postoperatively unfortunate suffer from inadequate descriptions of ear disease that were studied. In order to elucidate these questions and to give the surgeon deeper knowledge about how to handle CTN during surgery a prospective study is initiated on patients to be operated on with primary middle ear surgery.

We believe that patients with chronic otitis media and cholesteatoma has taste disturbance already before surgery due to the disease itself, of course depending on degree of the disease, and that patients with otosclerosis has a normal nerve function before surgery. We also believe that patients with normal taste before surgery are more likely to notice a taste disturbance and that a nerve in continuity after surgery, even if it is maltreated, gives less taste disturbance than a divided nerve. Two methods of taste measuring are used in the study, Electrogustometry (EGM) and a Filter Paper Disc method (FPD). We have evaluated EGM regarding possible bias and artifacts as well as the correlation regarding results from the two methods.

The study contains three substudies or arms.

1. A clinical prospective trial where 100 patients that undergoes primary middle ear surgery because of chronic otitis, cholesteatoma or otosclerosis are evaluated with EGM and FPD before and after surgery. They also answer a questionnaire about subjective taste disturbance and a questionnaire about quality of life.
2. A clinical multi center study on 200 patients that undergoes primary surgery because of otosclerosis. These patients answer a questionnaire about subjective taste disturbance and a questionnaire about quality of life.
3. A histological study with electron microscopy of CTN from healthy ears and from ears whit chronic otitis or cholesteatoma. We we plan to investigate samples from five healthy and from five sick ears with EM.