Serial MR imaging and 1H-MR spectroscopy in monozygotic twins with Tay-Sachs disease.

Four-year-old monozygotic female twins with early onset Tay-Sachs disease are described. The sisters showed similar slowly progressive clinical symptoms and deterioration, however the younger sister also demonstrated intractable myoclonus in the right leg. The serial MR images and (1)H-MR spectroscopy of the brain were obtained in both twins. MR images showed high intensity on T (2)-weighted image in the bilateral white matter, however there were no signal changes in the basal ganglia and thalamus during any of the phases. The ratio of N-acetylaspartate (NAA)/creatine (Cr) was decreased in the both white matter lesions and the corpus striatum, and that of myoinositol (mI)/Cr was increased in the damaged white matter on MR spectroscopy. The elevation of the lactate peak was clearly demonstrated in the left basal ganglia of the younger sister; however it was not shown in cerebral lesions of the elder sister. Changes in metabolites on MR spectroscopy were closely linked to the respective clinical features of each twin. Follow-up examination by (1)H-MR spectroscopy is useful for the evaluation of neuronal changes in children with Tay-Sachs disease.