Toe graphaesthesia as a discriminator of brain impairment: the outstanding feet for neuropsychology.

Because of the vulnerability of the medial surfaces of the cerebral hemispheres to the consequences of shear forces, we hypothesized that quantitative sensori-motor deficits for the feet would be strong indicators of general brain dysfunction. On the basis of the Halstead-Reitan Impairment Index, 28 adults who had received closed head injuries were assigned to perfectly normal, normal, or (mildly to severely) impaired groups. Foot tap and finger tap as well as agnosia and graphaesthesia for the fingers and toes were measured. Deficits in toe graphaesthesia were the most powerful group discriminator. Potential usefulness of haptic/motor, finger/toe comparisons for recording the progress of degenerative diseases, such as AIDS, is also suggested.