Electrophysiological evaluation of the visual system in Tay Sachs disease

Three patients with Tay Sachs disease diagnosed on clinical and enzymatic findings were followed during a trial treatment by enzyme replacement with purified hexosaminidase A enzyme extracted from human placentae. The electrophysiological investigation of the visual system was done utilizing standard techniques. The Visual Evoked Potentials (VEP) were extinguished in all the cases. The Electroretinograms (ERG) had normal configurations but abnormally large amplitudes, which increased with the progression of the disease. The possible neuronal mechanism responsible for this hypernormal ERG amplitude is discussed. No effects of the treatment on these electrophysiological visual parameters were observed.