Changes in the motor response to acute L-dopa challenge after unilateral microelectrode-guided posteroventral pallidotomy.

To determine the effect of unilateral posteroventral pallidotomy (PVP) on latency and duration of response to L-dopa ipsilateral and contralateral to the side of the lesion, six severe fluctuating Hoehn-Yahr IV patients with Parkinson's disease were evaluated 2 days before and after unilateral PVP. After an overnight drug holiday in a fasting state, patients were challenged with a single dose of 200/50 mg of L-dopa/ carbidopa. Sequential tapping tests every 5 minutes in both hands were used to measure changes in motor status. Duration of L-dopa effect was significantly longer after PVP (p < 0.03). Mean latency of the effect improved by 50% without reaching statistical significance. Despite a clear, asymmetric improvement of cardinal Parkinson's disease symptoms after unilateral PVP, changes in the dose-response L-dopa profile occurred symmetrically, suggesting that mechanisms underlying the two effects are distinct.