[Somesthetic evoked potentials of the spinal cord and cervico-brachial neuralgia].

Thirty patients with active cervico-brachial neuralgia were investigated by detection of the sensory action potential of the nerve, the spinal somaesthetic evoked potential and the cerebral somaesthetic evoked potential. Stimulation is applied to the affected side and symmetrically to the healthy side, at the finger and at the wrist. The digital stimulation recruits a more specific root territory (2nd finger C6-C7, 5th finger C8-T1). These results were compared to those obtained in a population of 14 controls. In cases of active cervico-brachial neuralgia, the spinal somaesthetic evoked potential from digital stimulation (N16) was always abolished in the painful territory; it was also abolished on the pain free side in 75% of cases, while it was present in 96% of the controls. The spinal somaesthetic evoked potential from stimulation of the wrist was only abolished on the painful side in 29% of cases, but the mean amplitude of N13 was reduced. In contrast, the cerebral somaesthetic evoked potential and the sensory action potential of the nerve were only minimally altered. These changes regress after clinical cure. There is a correlation between the severity of the clinical course and the electrophysiological findings. Isolated abolition of the spinal somaesthetic evoked potential from digital stimulation is a constant feature of benign cervico-brachial neuralgia, while abolition of the spinal somaesthetic evoked potential by stimulation of the finger and of the wrist, bilaterally, corresponds to the most severe forms.