Pallidal Deep Brain Stimulation for a Case of Hemidystonia Secondary to a Striatal Stroke

<b><i>Background:</i></b> The efficacy of bilateral globus pallidus internus (GPi) deep brain stimulation (DBS) for medically refractory idiopathic generalized dystonia has been demonstrated repeatedly. More variable outcomes have been reported in the treatment of secondary dystonia with GPi DBS. <b><i>Objectives:</i></b> The present study seeks to examine the pallidal physiology and clinical outcome of GPi DBS in a case of secondary dystonia. <b><i>Methods: </i></b>We report on a 43-year-old man who at the age of 9 suffered a left basal ganglia stroke and at the age of 21 developed severe disabling hemidystonia. Following unsuccessful medical management for many years and an axial involvement of the dystonia, he underwent bilateral GPi DBS with dual microelectrode mapping of cell firing and evoked field potentials (fEP). <b><i>Results:</i></b> On the intact side we found regular firing of pallidal neurons and normal fEP indicative of functioning striatopallidal pathways. The affected side was found to include a higher frequency of bursting pallidal neurons. fEP could not be evoked on the affected side, suggesting their origin to be striatal GABAergic afferents. <b><i>Conclusions:</i></b> The patient had marked benefit from bilateral GPi DBS, which suggests that the therapeutic effects of DBS were mediated by the intact pathways in this case of hemidystonia.