All patients showed progressive improvement in the days or weeks following the initiation of pallidal stimulation. The improvement in choreic movements usually occurred within several days, whereas the total improvement in axial posture dystonia took several weeks. At 6 months after surgery, the ESRS scores had decreased compared with baseline by more than 40% among the first 10 patients included. In accord with the 2-step open Fleming procedure, the trial was stopped, and we concluded that pallidal stimulation is an effective treatment for TD (α = .032 and β = .043). The mean ESRS score (P<.001) and the mean Abnormal Involuntary Movement Scale score (P<.001) decreased significantly after surgery. At 3 months after surgery, the decrease compared with baseline was 61% (range, 19%-86%) for the ESRS score (P = .002) and 56% (range, 32%-81%) for the Abnormal Involuntary Movement Scale score (P = .006). The improvement was maintained at 6 months, with decreases compared with a baseline of 61% (range, 44%-75%) for the ESRS score (P = .005) and of 56% (range, 33%-69%) for the Abnormal Involuntary Movement Scale score (P = .006) (Figure 1). All 10 patients (with caregiver assessment being provided for the patient who was partially anosognosic) considered that there was major improvement in their abnormal involuntary movements. Two patients were free of dyskinesia, and the others had mild abnormal movements that they considered not to be troublesome. Tardive dyskinesia suppressive treatment was reduced in 5 patients (Table 2). There was similar improvement in the dystonic and choreic components of TD. Compared with baseline, the ESRS dystonia score (component III) was decreased by 67% (range, 17%-93%) at month 3 (P = .002) and by 68% (range, 28%-89%) at month 6 (P = .006), and the ESRS choreic movements score (component IV) was decreased by 62% (range, 33%-91%) at month 3 (P = .006) and by 53% (range, 27%-75%) at month 6 (P = .006) (Figure 2). Six patients had mild parkinsonian symptoms and akathisia (component II of the ESRS) that had improved by 27% to 100% at 6 months after surgery. All active electrodes were located within the posterolateral part of the GPi (mean ± SEM coordinates, 20.1 ± 0.4 mm lateral to the median line, 15.3 ± 0.5 mm anterior to the posterior commissure, and 3.9 ± 0.4 mm below the bicommissural line). Continuous monopolar stimulation was applied in all of the patients (mean ± SEM voltage, 3.5 ± 0.2 V; pulse width, 150 microseconds; and frequency, 130 Hz at 6 months). At 6 months, the double-blind evaluation confirmed the efficacy of bilateral stimulation, with a mean decrease of 50% (range, 30%-66%) (P = .002) in the ESRS score when stimulation was applied compared with the off stimulation condition. Depressed mood improved in patient 1 (Montgomery-Asberg Depression Rating Scale score, 44 at baseline to 10 at 6 months after surgery) and worsened in 3 patients (from 3 to 26 in patient 2, from 14 to 23 in patient 5, and from 6 to 21 in patient 7) who did not meet DSM-IV criteria for major depressive disorder and did not require specific treatment except for the use of antidepressant therapy in 1 patient. None of the patients developed delusions or delirium during the postoperative period (mean ± SEM Positive and Negative Syndrome Scale score, 11 ± 1 before surgery and 10 ± 1 at 6 months after surgery). There were no marked changes in antipsychotic or antidepressant treatment. No changes were observed in the patients' cognitive status (mean ± SEM Mini-Mental State Examination score, 26.7 ± 0.9 before surgery vs 26.8 ± 0.4 at 6 months after surgery; Mattis Dementia Scale score, 130.5 ± 2.5 vs 134.8 ± 2.0; Frontal Assessment Battery score, 15.7 ± 0.6 vs 16.3 ± 0.3; and Frontal Behavior Scale score, 2.3 ± 0.6 vs 2.4 ± 0.7). Two serious adverse events occurred. Patient 5, with no beneficial effects of stimulation and in whom the position of the left lead was too lateral and anterior, had to have the lead reimplanted after 2 months (for this patient, the time to assessment was defined in terms of the time from lead reimplantation). In patient 1, a cable connection exerted painful traction, and the stimulator had to be fixed to the clavicle. In each case, the problem was fully resolved.