[Neurinoma of the trigeminal root with recurrent intratumoral hemorrhage. Case report]

Trigeminal neurinomas extending into multiple fossae: surgical methods and review of the literature

OBJECT

Since 1974, 27 patients with trigeminal neurinomas (TNs) have been treated at Keio University Hospital and ancillary institutes. In the present study the clinical features and developmental patterns of these 27 cases are analyzed, and the clinical features of 402 cases reported in the literature are reviewed. Based on the analysis of the developmental patterns of the TNs, the surgical strategy for a one-stage removal of TNs involving multiple fossae is described.

METHODS

Trigeminal neurinomas are classified into six types according to tumor location. Types M, P, and E are tumors involving a single compartment, that is, the middle fossa, posterior fossa, or extracranial space, respectively. Types MP (middle and posterior fossae), ME (middle fossa and extracranial space), or MPE (middle and posterior fossae and extracranial space) are tumors involving multiple compartments. Advances in neuroimaging technologies, such as magnetic resonance imaging, have revealed a high incidence of TNs extending into multiple fossae, namely 36.2% in cases reported since 1983 and 59% in the authors' series. All but one of the most recent 19 patients in this series underwent skull base surgery, whereas the remaining nine patients were surgically treated via the conventional subdural approach. The rate of total tumor removal and the clinical outcome were significantly better in those patients treated by skull base surgery than those treated by conventional surgery.

CONCLUSIONS

The TNs extending into multiple fossae can be totally removed using the following single-stage surgical techniques: Type MP by the anterior transpetrosal approach; Type ME by the zygomatic or orbitozygomatic infratemporal approach; and Type MPE by the zygomatic transpetrosal approach. In 12 of 13 cases involving multiple fossae in this series, total tumor removal was achieved using single-stage skull base surgery.

Frontotemporal epidural approach to trigeminal neurinomas

From 1980 through 1993 a series of 44 patients with trigeminal neurinomas was treated. Five of them were operated on for the remainder of the tumour as they had undergone previous surgery elsewhere, 35 were operated on for the first time, and 4 were not operated on for various reasons. An epidural approach to the neurinomas originating in the branches of the Vth nerve peripherally to the Gasserian ganglion (GG) was used. In the neurinomas originating in the GG or in the root of the Vth nerve, either an epidural-transdural approach or an epidural-transdural-transpetrous approach was used. All tumours operated on using the approach described in this article were completely removed. In 10 patients, the Vth nerve sensory deficits increased in comparison with preoperative deficits; in 9 their state remained unaltered; and in 11 the sensory function of the Vth nerve improved. In those patients who had experienced pre-operative atypical trigeminal pain, the pain disappeared after surgery. There was no additional treatment: radiosurgery, irradiation or chemotherapy. Histopathological examination did not reveal any malignant changes in the tumours in any of the patients. Based on our own experience and on the published data it is believed that the best treatment for trigeminal neurinomas is complete microsurgical removal of the lesion.