902 SEVERE CEREBELLAR DEGENERATION AND DELAYED ONSET ATAXIA IN HISTIOCYTOSIS X

A rare, and poorly understood syndrome of progressive cerebellar ataxia can be seen in pts. with Histiocytosis X. We report two patients who had bone involvement of the skull and orbit, and developed delayed onset (3 and 4 yrs from diagnosis) of progressive cerebellar ataxia, corticospinal tract abnormalities, and functional weakness. Pt. #1, diagnosed in 1969 at age 2, now wheelchair bound, has moderately severe cognitive deficits and a seizure disorder. Pt. #2, diagnosed in 1977 at age 4, now has progressive truncal ataxia and rt. hemiparesis. Brain CTs of both pts. show symmetric hypodense areas in the cerebellar hemispheres, including the dentate nuclei. The vermis, and cerebellar and perimesencephalic cisterns are normal. No pathologic calcifications, or supratentorial abnormalities are noted. Brain stem evoked potentials are abnormal in both.