Mixed neuronal-glial tumor of the fourth ventricle and successful treatment of postoperative mutism with bromocriptine: case report

Tumors composed of both neurocytic and astrocytic cells are uncommon and poorly understood. We describe the clinicopathologic features of a very rare rosette-forming glioneuronal tumor of the fourth ventricle and propose bromocriptine as a useful therapeutic agent for cerebellar mutism after posterior fossa surgery. A fourth ventricle tumor was incidentally discovered in an 18-year-old woman. Magnetic resonance imaging revealed ventriculomegaly and a solid tumor with low-intensity signals on T1-weighted images and high-intensity signals on T2-weighted images. There was slight gadolinium enhancement. The tumor was subtotally resected. Although its lower half was well circumscribed, its upper half manifested invasive growth. Histologically, 2 components were identified, synaptophysin-positive neurocytic cells forming perivascular pseudorosettes and glial fibrillary acidic protein–positive astrocytic cells with Rosenthal fibers. Overall, cellular atypia was minimal and the MIB-1 labeling index was low. On the basis of these histologic findings, the tumor bore striking similarity to the recently described rosette-forming glioneuronal tumors of the fourth ventricle. Postoperatively, the patient manifested cerebellar mutism. The administration of bromocriptine improved her neurological status dramatically. The natural history of rosette-forming glioneuronal tumors of the fourth ventricle is not yet fully understood. Therefore, careful and long-term follow-up monitoring of the tumor hosts is necessary. Bromocriptine therapy may promote recovery from mutism after posterior fossa surgery.