[Cryopallidotomy in Parkinson disease. Effect on somatosensory potentials].

The paper reports 4-years results of a pilot study concerning the influence of a stereotactic pallidotomy on somatosensory evoked potentials in idiopathic Parkinson's disease. Potentials were recorded through the scalp surface from sensorimotor cortex of both hemispheres. Amplitudes and latencies of early and late waves were compared before and after the surgery. The surgery was recommended after 4 years of L-dopa therapy when bradykinesia and rigidity of right leg led to gait difficulty and postural instability. The dominant features of the syndrome were accompanied by tremor, micrography, chorea and lower responsiveness to L-dopa. Following the surgery a clear improvement of motor activity was observed. Increase of 20-90 ms waves amplitudes and P45 latency prolongation of 6-11 ms appeared due to the attenuation of pallidal inhibition exerted upon the thalamo-cortical transmission and a new arrangement of a cortical motor program. These electrophysiological changes, correlated with a clinical amelioration, may indicate as a favourable prognosis for a patient. Five months after pallidotomy a slight decrease of amplitudes occurred in relation to the previous examinations. Four years after surgery increase of most amplitudes and latencies and reconfiguration of later waves were related to deterioration of clinical course and worsening of left-side signs. We believe that somatosensory evoked potentials change may be a sensible indicator of motor state in Parkinson's disease. As far as we know the present study is one of the first presentation of somatosensory evoked potentials after pallidotomy.