Electrophysiological studies of peripheral nerves in patients with organic mercury poisoning.

Nineteen patients with organic mercury poisoning were examined clinically and electrophysiological studies were carried out on their peripheral nerves. Four severely affected patients were disorientated, restless, and unable to speak. Vision was abnormal in nearly half the patients, usually consisting of gross constriction of visual fields with preservation of central acuity. Severe cerebellar abnormalities were present in most. Paraesthesiae were common. On sensory examination, all except three patients had one or more of the following abnormalities: reduced appreciation of pin prick peripherally, defective position sensation, abnormal two-point discrimination, astereognosis. Vibration sensation was normal in all. Despite these sensory findings no electrophysiological abnormality was demonstrated in the peripheral nerves. It is suggested that the sensory disturbances are predominantly or entirely due to damage to the central nervous system.