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The treatment of persistent vascular hemidystonia–hemiballismus with unilateral GPi deep brain stimulation

We describe a case of a severe refractory hemidystonia–hemiballismus resulting from hemorrhage of the right subthalamic nucleus, which was managed with unilateral globus pallidus internus (GPi) deep brain stimulation (DBS). A 56-year-old man with a history of hypertension presented with a sudden onset of headache, left hemiparesis, and dysarthria. A brain computed tomography (CT) scan showed a small focal hematoma in the right pons, midbrain, and subthalamic region. The hemiparesis and dysarthria improved over several days, although not to normality. Four days after presentation, he started to notice left sustained twisting of the wrist, posturing of the arm, held in extension, and sudden flinging movements of the whole arm. This progressed over weeks to reach a stable but disabling level that affected his balance whilst walking, and which prevented him from performing bimanual tasks since the left arm would suddenly deviate outwards. He underwent inpatient neurorehabilitation and was discharged home 1 month later, but continued to have severe ballistic movements despite maximum tolerated medication including tetrabenazine (37.5 mg/tds), haloperidol (3 mg/tds), orphenadrine (50 mg/tds), and botulinum toxin (500 U to left pectoralis). The arm was prone to frequent trauma due to uncontrollable movements. After 3 years of unsuccessful medical therapy, he was referred for functional neurosurgery and underwent multidisciplinary evaluation for DBS. Physical examination revealed no contractures but on attempting to use his arms even minimally, he would develop a 908 flexed posture of the left wrist, and an externally rotated extended left arm (reminiscent of a waiter’s tip), which would suddenly deviate backwards and laterally. There were some milder dystonic and choreic movements of the left leg. He walked with his arm firmly adducted to the body with the elbow in full extension. There was no spasticity in the limbs, and the remainder of the neurological examination was normal (Supporting Information Video). Brain MRI showed a focus of low signal on T2 and FLAIR within the right side of the midbrain with extension into the substantia nigra and subthalamic nucleus (STN) consistent with hemosiderin deposition following previous hemorrhage (Fig. 1A). Magnetic resonance angiography, neuropsychological, and neuropsychiatric testing revealed no abnormalities precluding DBS. Three years after the onset of his symptoms, a quadripolar DBS electrode (Medtronic 3389) was placed in the right GPi using direct MRI guided targeting under general anaesthesia (Fig. 1B). The battery was implanted in the same session. There were no complications. The DBS was switched on 2 days postoperatively. The initial parameters were case positive, contact one negative, amplitude 1.5 V, pulse width 60 ls, frequency 130 Hz. An improvement was noted in the involuntary movements within days, with the patient being able to perform the ‘‘finger-nose’’ test with the left hand. Regular physiotherapy was provided, and the amplitude was gradually increased to 4.5 V over the next 6 months, at which time the ballistic movements had been eliminated, although the dystonic posturing of the left wrist persisted (Supporting Information Video). Some functionality was restored, and the patient could hold pans, open doors, and walk with more ease without injuring the left arm. Standardized measures of symptom severity were not used in this case because of the lack of such scales for ballism, which was the predominant problem. However, the benefit of surgery is apparent in the videos that demonstrate the transition from the preoperative state, in which the left arm is unusable and susceptible to frequent trauma, to the postoperative state in which the patient can use the left arm purposefully. His clinical condition has remained stable at 15 months follow-up. The patient clinically had hemidystonia and hemiballismus. Phasic dystonia has been shown to respond to GPi DBS, hence our view to offer this treatment. Ventrolateral thalamotomy and posteroventral pallidotomy have been shown to improve hemiballismus arising from STN lesions, but we are not aware of any GPi DBS reports for persistent hemidystonia–hemiballismus, possibly due to the rarity of this condition. The incidence of refractory hemiballismus after stroke was 0.04% in a large series. This case demonstrates the efficacy of GPi DBS for hemiballismus associated with phasic dystonia. The persistence of dystonic posturing in this case suggests that the response of dystonia may not be immediate but could improve with time, presumably due to plastic changes within the basal ganglia and thalamo-cortical loops.