Neuropathy of the facial nerve in chronic otitis media without associated facial paralysis. A human temporal bone study

The chorda tympani degenerates during chronic otitis media: an electron microscopy study

CONCLUSION

Chorda tympani nerve specimens from ears with chronic inflammatory middle ear disease exhibit structural signs of degeneration. These correlate well with taste disturbance. Simultaneously, they exhibit signs of regeneration, which may explain the ability for taste recovery.

OBJECTIVES

The chorda tympani, the major taste nerve, runs uncovered through the middle ear cavity. This situation exposes it to various forms of middle ear pathology. A difference has been noticed regarding taste symptoms pre- and postoperatively between inflammatory and non-inflammatory diseases. The present study aimed to investigate ultrastructural changes of chorda tympani in different forms of inflammatory middle ear disease, such as chronic suppurative otitis media and cholesteatoma, 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 and electron microscopy were performed.

RESULTS

For all five nerves from diseased ears, microscopy showed a higher percentage of axon and myelin sheath degeneration than in the normal controls. Furthermore, three of the five also exhibited sprouting.

Ultrastructural Analysis of the Chorda Tympani Nerve in Chronic Suppurative Otitis Media

OBJECTIVE

To compare ultrastructure of the chorda tympani nerve by light and electron microscopy in patients with otosclerosis and chronic suppurative otitis media.

STUDY DESIGN

Comparative prospective study.

SETTING

Tertiary care, referral medical center.

PATIENTS

The tympanic segments of chorda tympani nerves were collected for ultrastructural investigation in 20 cases with chronic suppurative otitis media and 10 cases with otosclerosis that underwent middle ear surgery.

RESULTS

Histopathologic examinations of the suppurative group showed that unmyelinated fibers were almost totally lost and replaced by collagen fibers. The thickness of the myelin sheaths was very slender, whereas some of them were atrophic. A substantial increase was encountered in the endoneural collagen substance and connective tissue, whereas inflammatory elements and edema were present occasionally. Degenerative alterations of the myelinated fibers mainly occurred in the form of adaxonal vacuoles. There was disorganization and separation of parallel lamellae of Schmidt-Lanterman clefts.

CONCLUSION

The chorda tympani nerve should be preserved in otologic surgery. However, inadvertent dissection of the chorda tympani nerve in chronic suppurative otitis media surgery will not possibly cause a postoperative disturbance in light of ultrastructural changes that occur in the nerve.

Histopathological changes of chorda tympani in chronic otitis media

OBJECTIVE

To investigate whether histopathological changes of chorda tympani might exist in patients with chronic otitis media without facial paralysis.

STUDY DESIGN

The study was designed as a prospective trial.

METHODS

Twenty of 107 patients with chronic otitis media, in whom the chorda tympani were injured inadvertently during middle ear surgery, were enrolled into the study. The cases were divided into two groups based on the activity of chronic infection at the time of surgery. Twelve cases with suppurative disease were included in group I, and 8 cases with dry ear in group II.

RESULTS

Histopathological examinations of the specimens revealed findings such as thickening of perineural and epineural connective tissue, vacuolar degeneration of Schwann cells, and proliferation of fibroblasts in endoneurium. Disorganization of the axons of some nerve fibers was also determined.

CONCLUSION

Based on the histopathological changes of chorda tympani in chronic middle ear disease, it is postulated that chronic otitis media may give rise to functional loss of the nerve.