Tumours of the fifth cranial nerve.

Tumours of the fifth cranial nerve are very rare, comprising only 0.2% of all intracranial neoplasms. The authors critically review the literature, and report on 12 personal cases of trigeminal tumours (nine neurinomas, one meningioma, one epidermoid, one osteochondroma). General pathology, symptoms, and signs are analyzed, and compared with cases from the literature. Because of their insidious onset and slow "illogical" progression of misleading symptoms, trigeminal tumours often prove to be a diagnostic challenge. As a consequence they usually reach a large size before causing sufficient symptoms to lead the patient to a neurosurgical clinic. The diagnosis is therefore likely to be made by radiological investigations. The typical radiological feature (on plain skull films, pneumoencephalography, and angiography) are described, and differential diagnosis is discussed. All the patients in the present series were operated on. Surgical procedures and postoperative results are discussed.