Pathophysiological mechanism of ipsilateral cerebral and brainstem hemiatrophy in basal ganglia germ cell tumors: case report.

INTRODUCTION: The basal ganglia is an uncommon location for germ cell tumors. It has been reported that basal ganglia germinomas and mixed germ cell tumors are associated with ipsilateral cerebral and brainstem hemiatrophy on presentation. Several pathophysiological mechanisms including autoimmune process and direct tumor infiltration of the thalamus or the internal capsule have been postulated to explain this association. CASE REPORTS: The authors report two boys, aged 7 and 10, with basal ganglia germ cell tumors. Both of them presented with gradual onset of hemiparesis and had features of ipsilateral cerebral and brainstem hemiatrophy on imaging studies. They underwent chemotherapy followed by reduced dose radiotherapy with good response. DISCUSSION: Pathophysiological mechanisms of the associated ipsilateral cerebral and brainstem hemiatrophy are discussed. The authors postulate that the gradual obliteration of the perforating arteries to the diencephalon especially the lenticulostriate arteries of the prebifurcation middle cerebral artery may be the major mechanism of the associated hemiatrophy.