Deep Brain Stimulation

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Shouyan Wang, Xuguang Liu, John Yianni, Alex L. Green, Carole Joint, John F. Stein, Peter G. Bain, Ralph Gregory and Tipu Z. Aziz

Object

The object of this study was to identify a preoperative physiological index by using surface electromyography (EMG) signals that would correlate with clinical outcome in dystonic patients following bilateral pallidal stimulation.

Methods

In 14 patients with spasmodic torticollis, generalized dystonia, and myoclonic dystonia, surface EMG signals were recorded from the most affected muscle groups. Although the dystonia affected different body segments, the EMG signals in all patients could be decomposed into bursting and sustained components. Subsequently, a ratio of the EMG amplitude was calculated between the two components and then correlated with clinical outcome.

Patients who experienced rapid improvement following bilateral pallidal stimulation had a significantly higher EMG ratio compared with those who did not. Furthermore, a significant correlation was found between the EMG ratio and clinical improvement during the 12-month period following pallidal stimulation.

Conclusions

The authors concluded that surface EMG studies could be used to predict the clinical outcome of and to select patients for pallidal stimulation for dystonia.

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Dipankar Nandi, Simon Parkin, Richard Scott, Jonathan L. Winter, Carole Joint, Ralph Gregory, John Stein and Tipu Z. Aziz

✓ The authors report the neurological, neurophysiological, and neuropsychological effects of using long-term bilateral pallidal high-frequency deep brain stimulation (DBS) in a case of disabling camptocormia. Deep brain stimulation electrodes were implanted stereotactically to target the globus pallidus internus (GPi) bilaterally. Local field potentials (FPs) were recorded using the DBS electrodes and concurrent abdominal flexor electromyography (EMG) potentials during camptocormic episodes. Videotaped assessments of the movement disorder and neuropsychological evaluations of the patient before implantation and 6 months after initiation of pallidal stimulation were recorded.

There was significant functional improvement following long-term pallidal stimulation, and some improvement was noted in neuropsychological scores. A temporal correlation between the GPi FPs and EMG-recorded rectus abdominis potentials was evident. There were no treatment-related adverse effects. The authors have found that long-term pallidal stimulation was safe and offered functional benefit to a patient with this severely disabling condition. The physiological studies may help further the understanding of the pathophysiology of this rare entity.