[Polyesthesia--report of two cases].

Polyesthesia is an abnormal sensation in which a single sensory stimulation seems to be felt as several ones. We report two cases showing this rare phenomenon. The first case was a 34-year-old man having a history of SLE for 20 years. When he was 22 years old, he suffered from transverse myelopathy at the tenth thoracic level. Two years after this episode, he noticed a curious sensory experience. Namely, when he rubbed his hand or lateral trunk, similar sensation occurred on the foot of the same side simultaneously. This phenomenon has continued for ten years. The characteristics of this double sensation were as follows; effective modes of stimulation were rubbing, tapping and vibration. Pinprick or cold/warm stimuli could not elicit any sensation on the foot. The sensation observed on the foot was always ipsilateral and simultaneous in almost symmetrical distribution. Rubbing the foot could not elicit any sensation on the hand or trunk. Somatosensory evoked potentials (SEPs) following tibial and peroneal nerve stimulation could not be recorded on the scalp. Dermatomal SEPs below the tenth thoracic level were also silent over the scalp. SEPs obtained by median nerve stimulation were normal bilaterally. Various neuroradiological examinations including CT and MRI were noncontributory. This phenomenon, diagnosed as synesthesia, may be related to denervation supersensitivity after spinal cord lesion and sprouting from the fibers conveying hand and thoracic information to those denervated neurons at the posterior column nuclei. The second case was a 70-year-old woman having a history of syphilis. She noticed a characteristic sensation for ten years. Namely, when she rubbed her face, especially her forehead and cheeks, another sensation occurred 1 second after primary stimulation at the same place.(ABSTRACT TRUNCATED AT 250 WORDS)