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Surgery for movement disorders: new applications?
  1. P Limousin-Dowsey,
  2. S Tisch
  1. Institute of Neurology, London, UK
  1. Correspondence to:
 P Limousin-Dowsey
 Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, Box 146, Queen Square, London WC1N 3BG, UK; p.limousinion.ucl.ac.uk

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The effect of basal ganglia surgery on Tourette syndrome, tardive dyskinesias, and myoclonus–dystonia

The last 15 years have been a period of significant advances in functional neurosurgery for movement disorders largely due to the development of the technique of deep brain stimulation (DBS) and the refinement of the targeting procedure. Deep brain stimulation is now well established for the treatment of Parkinson’s disease, tremor, and primary dystonia, and is progressively being used for new applications. In this issue, Houeto et al1 (pp 992–5) present a case report on the effect of basal ganglia surgery on Tourette syndrome, Lenders et al2 (p 1039) on tardive dyskinesias, and Magarinos-Ascone et al3 (pp 989–91) on myoclonus–dystonia.

Tourette syndrome is a disabling movement disorder—the signs include motor and vocal tics and various behavioural dysfunction. Ablative procedures have been carried out in the frontal area or the thalamus. An earlier report has shown an improvement of tics in three patients following thalamic DBS.4 In the present study Houeto et al1 compared the effect in two targets—the centromedian-parafascicular complex of the thalamus (Ce-Pf) and the antero-medial part of the internal globus pallidus (GPi)—both part of the limbic basal ganglia-thalamo-cortical loop.1 They conducted a double blind study of four periods with different conditions of stimulation: off-stimulation, GPi stimulation, Ce-Pf stimulation, and GPi and Ce-Pf stimulation. GPi stimulation or Ce-Pf stimulation improved tic severity by 70%, improved coprolalia, and eliminated self injuries. Emotions and depression were improved with Ce-Pf stimulation. Lenders et al2 report on a patient with tardive dyskinesias, predominantly dyskinetic in the right hemibody treated by left pallidotomy with 5 years follow up of good improvement.2 Few cases had been previously reported. Magariños-Ascone et al3 report the improvement of a myoclonus–dystonia syndrome by GPi stimulation, confirming earlier reports.

These studies are all case reports and although encouraging the results are limited by virtue of the sample size. In rare disorders such as these a multicentre study would allow a larger number of patients to be followed. The best target for Tourette syndrome certainly needs additional data to support this early finding. Other issues exist with Tourette syndrome and tardive dyskinesias that often include debilitating psychiatric problems. Patients with psychiatric problems may become preoccupied with the DBS implanted system and could even develop delusions that DBS is exerting “mind control”. Therefore it is particularly important in those patients to have a multidisciplinary team to discuss the specific ethical issues, establish strict criteria of selection, and evaluate the impact of surgery on all aspects of the disease. For some conditions improved rating scales may need to be developed to better quantify clinical outcome after surgery. The impact on cognitive and behaviour functions also need to be carefully documented. Unilateral pallidotomy involves a one off procedure and no implanted equipment, and might still have a place in experienced hands and selected cases like Lenders et al.2 Many questions remain on the mechanism of action of basal ganglia and thalamic surgery, and in particular how can they improve such a variety of conditions.

The effect of basal ganglia surgery on Tourette syndrome, tardive dyskinesias, and myoclonus–dystonia

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