[A case of basal encephalomeningocele (a transethmoidal type) containing the olfactory nerve].

An experience of operative case of basal (transethmoidal type) encephalomeningocele is reported. A 3-year-old boy complained of continuous, spontaneous cerebrospinal fluid rhinorrhea and right intranasal mass lesion. The rhinorrhea began when one year old. He suffered from meningitis at the age of two. When he was three years old, the intranasal mass and CSF rhinorrhea were perceived. On admission he had normal general status and no abnormality in neurological examination. The usual axial computed tomography showed a small mass in the intranasal cavity. But the continuity between the mass and brain parenchyma was not detected in this study. Metrizamide CT cisternography demonstrated it. Coronal CT scan visualized it more directly. We performed operation using bifrontal craniotomy and subfrontal approach. Brain parenchyma did not protrude into the frontal cranial base and expanding right olfactory nerve penetrated into the small defect at the right cribriform plate. The olfactory nerve was extracted as much as possible. The defect was filled with a few piece of muscle and coating with the adhesive agent was performed. Histological findings of operative specimen were abnormal olfactory nerve, normal brain tissue and arachnoid membrane. Post-operative state was uneventful. CSF rhinorrhea disappeared. Post-operative direct sagittal computed tomography visualized the encephalomeningocele extremely. Biopsy of the intranasal mass revealed brain tissue covered by normal nasal epithelium. Basal encephalocele is rare in Japan. We found 10 cases in the literature. It is important that we do not forget basal encephalocele in the difference of intranasal tumors.(ABSTRACT TRUNCATED AT 250 WORDS)