Learning Objectives: Patients with chronic inflammatory middle ear diseases can experience taste disturbance before surgery due to the degenerative capacity of the inflammatory process.

Background: The important nerve of taste, the chorda tympani nerve, runs uncovered through the middle ear. This location predisposes it to become affected by bacterial toxins, enzymes and mechanical damage in various forms of middle ear pathology, such as chronic otitis media and cholesteatoma. A difference between inflammatory diseases, such as chronic suppurative otitis media and cholesteatoma, and noninflammatory diseases, such as otosclerosis, regarding taste disturbance preoperatively and symptoms postoperatively have been noticed. The present study aims to investigate ultrastructural changes of chorda tympani in inflammatory middle ear disease as compared with normal.

Methods: Five chorda tympani specimens were collected from healthy middle ears of patients subjected to surgery for acoustic neuroma to be used as normal controls, and five from middle ears with chronic otitis media or cholesteatoma where the nerve could not be saved during the operation. Light microscopy and electron microscopy were used to identify signs of pathological processes.

Results: Ultrastructural changes that implicate inflammatory changes and degeneration were found in all five nerves from ears with chronic otitis media and cholesteatoma. There were signs of proliferation of connective tissue of the endoneurium, disorganization and demyelination of axons, vacuolar degeneration of the axons, myelin sheath disintegration and edema. As a sign of regeneration capacity there was occurrence of sprouting in CTN from ears with inflammatory diseases.

Conclusion: Chorda tympani nerves from ears with chronic inflammatory middle ear disease exhibit structural signs of deterioration that correlates well to taste disturbances.

There were signs of nerve regeneration that could explain the ability of taste recovery.