EVOKED-POTENTIALS IN A SUBJECT WITH A LARGE-FIBER SENSORY NEUROPATHY BELOW THE NECK

The results from experiments in various modalities of evoked potential s are described in a subject with a complete large peripheral neuropat hy below the neck. He has no tactile or position sensitivity below tha t level, but has retained fatigue, pain, and temperature sensation. Pe rcutaneous electrical stimulation of peripheral nerves led to scalp re corded evoked potentials with thresholds and propagation velocities co mpatible with conduction along A-delta peripheral pathways. CO2 laser evoked potentials were similar to those seen in controls, further supp ort for intact A-delta peripheral fibres. Movement-related cortical po tentials (MRCPs) were recorded associated with active and passive move ment of the middle finger. The former were normal, evidence that the t ermination of the MRCP is not dependent on peripheral feedback. By com paring passive MRCPs between controls and the subject it was possible to establish which parts of the potentials are visual and which are pr oprioceptive and to gain evidence of central reorganisation in the sub ject. Magnetic brain stimulation was used to show that the subject did not perceive induced movement, had a normal centrally originating sil ent period, and could focus his attention during real and imagined mov ement of the finger more successfully than could normal controls.