Ultrastructural analysis of the chorda tympani nerve in facial paralysis from different etiologies.

Twelve chorda tympani segments, removed from as many patients (7 females, 5 males) affected by otosclerosis (3, as controls) and from either idiopathic (4), or traumatic (3) or herpetic (2) facial paralysis, were examined by a transmission electron microscope, in order to verify chordal ultrastructural changes, the gravity of neural damage in the various types of facial paralysis and the role played by chorda tympani on the etiopathogenesis of the idiopathic form. The segments were obtained, while performing a stapedectomy in otosclerotic patients and, in facial palsy, while performing chordal neurotomy or direct decompression of the II and III portio of the VII nerve. The obtained data showed no noteworthy alterations concerning myelinated and unmyelinated nerve fibers and chordae stroma in otosclerotic patients, confirming their reliability as controls. In facial paralysis, both normal ultrastructures and alterations were noticed, even though polymorphic: unravelling and dissociation of the lamellae sheaths up to a point of degeneration with a more or less complete resorption of myelin, accumulation of dense bodies and electron-dense formation, particularly in unmyelinated fibers, vacuoles in myelinated fibers, intracytoplasmic vacuoles in Schwann cells and, in herpetic forms, an occasional presence of inflammatory cells. Such results demonstrate that, in any type of facial paralysis, the ultrastructure of the chorda tympani is constantly involved, probably due to main trunk involvement. In the idiopathic forms the alterations of the chorda look like to degenerative alterations caused by traumato-ischemic events, rather than to cytopathic lesions induced by herpetic virus.(ABSTRACT TRUNCATED AT 250 WORDS)