ARACHNOIDAL CYST IN THE DIFFERENTIAL-DIAG NOSIS OF ISCHEMIC OPTIC NEUROPATHY IN A TYPE-II DIABETIC

History and clinical findings: A 71-year-old woman, a diabetic (type I Ib) for 27 years. developed bilateral hemianopsia over a period of abo ut 2 years. A few weeks before hospital admission the defect in her vi sual fields increased more rapidly and double vision occurred intermit tently. The hemianopsia was demonstrated by finger perimetry. There wa s no evidence of heart failure or peripheral vascular disease. Muscle reflexes were normal, but there was a decrease in vibratory sensation in both feet. The cause of the visual disturbance was at first thought to be an ischaemic optic neuropathy. Investigations: Biochemical test s showed an HbA(1) of 12.8%, blood sugar levels were between 230 and 3 59 mg/dl, and there was increased intravascular platelet activation. O phthalmological examination confirmed bitemporal hemianopsia and early retinopathy. Magnetic resonance imaging of the skull revealed an intr a- and suprasellar cystic space-occupying lesion extending to the righ t optic chiasma. These findings, taken together, indicated an arachnoi dal cyst. Treatment and course: After the diabetic metabolic state had been normalized with insulin treatment (average of 30IU of an interme diary insulin) and dietary measures, the cyst was evacuated stereotact ically. The hemianopsia quickly improved markedly and the patient was discharged 4 days after the operation with her vision nearly fully res tored.