Successful deep brain stimulation of the globus pallidus internus in a patient with adult onset primary axial dystonia

Axial dystonia is a rare manifestation of adult onset primary segmental dystonia. Typically patients present with craniocervical dystonia spreading to the trunk but not to the extremities. Affected patients are disabled predominantly by flexion spasms of the trunk which are worsened on action especially during standing and walking. Response to drug therapy is often poor and local botulinum toxin injections are of limited value in these patients. Here we report a patient with axial dystonia who was successfully treated with deep brain stimulation (DBS) of the globus pallidus internus bilaterally (GPi). This 39 year old woman presented with a three year history of truncal spasms with predominant flexion and lateral bending of the trunk. Onset was subacute during her first pregnancy. There was gradual spread of dystonia from back muscles to both shoulders and also to the neck, although axial dystonia continued to be the most relevant problem. Three years into her disease action induced dystonia was so severe that she was hardly able to walk because her trunk was flexed by almost 90° and also severely bent to the left side whenever she attempted to walk. There was no dystonia in arms or legs apart from mild bilateral dystonic posturing (Fahn-Marsden Score: 21). Extensive laboratory investigations were unrevealing. No mutation in the DYT1 gene was found. Medical treatment with zolpidem, zopiclone and bromazepam did not improve her symptoms. In view of symptom severity we opted for bilateral implantation of DBS electrodes in the GPi given previous favourable reports of GPi stimulation in patients with primary generalised and focal dystonia. Post-operatively, symptoms improved within the first few days. There was further improvement over the following 3 months. Subjectively, the patient reported an improvement of 95%. Currently, she has mild torticollis, dystonic posturing of her left arm, mild dystonia involving the right shoulder and mild axial dystonia with marginal trunk bending to the left on action (Fahn-Marsden Score: 4). Gait and posture and the remainder of the neurological examination are otherwise normal.

To the best of our knowledge this is the first report of a patient with adult onset primary axial dystonia who underwent GPi DBS. Outcome was excellent so that this treatment should be considered in these patients who are otherwise difficult to treat.