Long-term high-frequency bilateral pallidal stimulation for neuroleptic-induced tardive dystonia. Report of two cases

The authors report the results of long-term bilateral high-frequency pallidal stimulation in two patients affected by neuroleptic-induced dystonia. The first patient, a 33-year-old man, experienced a dystonic posture of the trunk, with involvement of the neck and upper and lower limbs after 11 years of treatment with neuroleptic drugs. The second patient, a 30-year-old man, presented with a torsion dystonia, spasmodic torticollis, and involuntary movements of the upper limbs, which appeared after 4 years of neuroleptic treatment. Both of these dystonias worsened even after the neuroleptic treatment had been discontinued, and neither patient responded to clozapine or benzodiazepine therapy. The time lapse between the first appearance of dystonia and surgery was, respectively, 5 and 3 years. In each case bilateral stereotactic implantation of electrodes within the globus pallidus internus (GPI) was performed while the patient was in a state of general anesthesia. The electrodes were placed at the following anterior commissure-posterior commissure line-related coordinates: 20 mm lateral to the midline, 6 mm below the intercommissural plane, and 3 mm anterior to the midcommissural point. Electrical stimulation (130 Hz, 1 V, 90 microsec) was begun on the 1st postoperative day. In both patients, a genetic analysis positively ruled out a mutation in the DYT1 gene, and magnetic resonance imaging yielded normal findings in both cases. Extrapyramidal symptoms and dystonia disappeared almost completely and dramatically in both patients just a few days after high-frequency bilateral pallidal stimulation commenced. Both patients regained autonomy and neuroleptic treatment was reinitiated. The follow-up period for both cases was 1 year. Long-term bilateral high-frequency stimulation of GPI resulted in a dramatic and long-lasting improvement of neuroleptic-induced tardive dystonia.