Occult perineural tumor infiltration of the trigeminal nerve. Diagnostic considerations.

Cutaneous carcinomas of the face, and some nasopharyngeal carcinomas, may present with facial dysesthesias and/or facial nerve palsies in the absence of visible masses. Even with frank ophthalmoplegia, occult tumors that present in this matter may elude detection, for which reason specific diagnostic studies must be employed. We report seven cases of trigeminal nerve infiltration by occult tumors (five squamous cell carcinomas, one basal cell carcinoma, and one adenoid cystic carcinoma), and outline the clinical course, diagnostic investigations, and the subsequent management of these patients. The importance of establishing an early diagnosis before the tumor has transgressed the basal foramina is emphasized, as tumor infiltration of the cavernous sinus carries a more guarded prognosis. The use of magnetic resonance imaging to identify involved peripheral nerve branches that may then be biopsied is suggested. The patho-physiological mechanisms of neurotropic spread of tumor are reviewed.