Abstract
Two cases of primary reticulum cell sarcoma of the nervous system are presented because of their unusual clinicopathological correlations. Consecutive pupil-sparing third nerve paralysis was associated with tumour infiltrating the diencephalon and mesencephalon and the fascicular portions of both oculomotor nerves in the first case. Concomitant sympathetic involvement, as evidenced by relative miosis, cannot account for the preserved pupillary reactions. Preservation of the pupils was most likely the result of the intrinsic rather than compressive, third nerve involvement. In the second case involvement of the right facial colliculus was associated with the `one-and-a-half' syndrome (combined lateral gaze palsy and unilateral internuclear opthalmoplegia) and peripheral facial nerve paralysis. Terminally, the left lateral rectus muscle was also involved, and a discrete tumour implant had extended well beyond the midline.