A comparative study of median nerve somatosensory evoked potential in the totally blind and normal subjects.

The totally blind individuals are often considered to be compensated for their visual loss by augmentation in the auditory and tactile perceptions as against the normal sighted individuals. The objective of the present work was to study the somatosensory evoked potentials (SEPs) after median nerve stimulation in the wrist of totally blind and normal sighted individuals. SEPs were recorded after median nerve stimulation in the wrist of 15 Braille reading totally blind females and compared with 15 age matched normal sighted females. Latency and amplitudes of SEPs (N9, N13, and N20) were measured and analyzed statistically. Amplitude of N20 SEP was significantly larger in the totally blind than in normal sighted individuals (P < 0.05). The amplitudes of N9 and N13 SEPs and the latencies of all SEPs showed no significant differences. The congenitally blind individuals have larger N20 amplitude, suggestive of greater somatosensory cortical representation than normal sighted individuals.