SUBTHALAMIC NUCLEUS OR INTERNAL PALLIDAL STIMULATION IN YOUNG ONSET PARKINSONS-DISEASE

The aim of this study was to compare, retrospectively the value of chr onic bilateral stimulation of the internal globus pallidus (GPi) and t he subthalamic nucleus (STN) in patients with young onset Parkinson's disease. We selected 13 consecutive patients with similar characterist ics at the rime of surgery: age at onset <40 years, disabling motor fl uctuations (Hoehn and Yahr stage 4 or 5 in off-drug phases) and levodo pa-induced dyskinesias (LID). Eight patients were operated on in the S TN and five in the GPi. The Unified Parkinson's Disease Rating Scale ( UPDRS), timed motor tests and a LID scale were compared in on-and off- drug conditions before surgery and 6 months after surgery on stimulati on using the chronic electrical parameters found to improve best the m otor stare of the individual patient, without adverse effects. In off- drug phases, the motor score of the UPDRS was improved by 71% with STN stimulation and by 39% with GPi stimulation on average. This differen ce was statistically significant (P < 0.05). Whereas rigidity and trem or showed good improvement in both groups, the decrease in the akinesi a score pl,ns more pronounced in the STN group. In the STN group, the improvement of all motor symptoms was very close, or equal, to the bes t levodopa response. Thus the levodopa test was predictive of outcome. The improvement in off-drug period motor handicap allowed a decrease in the levodopa-equivalent dose only in the STN group (-56%). The volt age, frequency and pulse width used for chronic stimulation were lower in the STN group. In the on-drug phases,there was a marked improvemen t in LID in the GPI group, as measured by the dyskinesias score during an acute levodopa rest, whereas there was only a small decrease in th e STN group (P < 0.05). However; in the long term, the reduction of le vodopa dosage in the STN group led to an indirect reduction of LID sim ilar to that in the GPi group during activities of everyday life. In c onclusion, the overall results favour the neurosurgical treatment of P arkinson's disease by stimulating the STN rather than the GPi.