LAUSR

Spino-cerebellar ataxia type 3 (SCA3) is a polyglutamine repeat neurodegenerative disorder sometimes associated with pyramidal signs and dystonia [3]. Deep brain stimulation (DBS) of the globus pallidus internus (GPi) has been shown to be an effective treatment for reducing symptoms of generalized, focal, or segmental dystonia [4]. We report the case of a patient suffering from a medically refractory generalized dystonia related to SCA3 and improved by GPi-DBS. A 19-year-old man with a positive family history of SCA3 presented with cervical dystonia. SCA3 was confirmed by a heterozygous amplification of CAG (79 ± 3) in ATXN3. Within a year, his clinical state had worsened considerably with generalized dystonia involving the four limbs, the trunk and the face. In addition, cerebellar ataxia and pyramidal signs had also appeared, rapidly leading to major functional limitations including recurrent falls and swallowing difficulties. Despite maximal doses of anticholinergic drugs and botulin toxin injections, medication failed to stabilize the patient who underwent bilateral GPi implantation of a quadripolar electrode (Medtronic Inc. 3389) 1 year later. The leads were implanted stereotactically within the ventro-postero-lateral part of the GPi. The patient was evaluated before and 12 months after surgery by two independent neurologists expert in movement disorders and DBS programming (DG, PB). The best results were obtained with the following settings: (1) right lead, contacts 5 and 6, pulsewidth 210 μs, frequency 130 Hz, amplitude 2 V; (2) left lead, contacts 1 and 2, pulsewidth 210 μs, frequency 130 Hz, and amplitude 2.6 V. Kinematic analysis data are shown in Fig. 1. The dystonic symptoms progressively improved from 3 to 12 month following surgery as attested by Burke–Fahn–Mardsen (BFM) scores (presurgical = 72; 12 months after surgery = 32). The patient was able to stand up without help and his swallowing improved dramatically. However, his cerebellar ataxia did not improve. Kinematic data objectively confirmed these observations. Unfortunately, during the second year after surgery, painful generalized dystonia progressively reoccurred despite changes to the stimulation settings (additional contact more ventrally and pulse duration increase). These results indicate that bilateral stimulation of the GPi is partially and transitorily effective in reducing the severity of generalized dystonia in patients affected by SCA3. GPi-DBS is a well-established treatment for various types of dystonia [4, 7], but is rarely used in dystonia related to SCA [2]. The patient’s clinical improvement was confirmed by the reduction in BFM score obtained after surgery and the decrease in kinematic parameters assessed on the upper and lower limbs in both the standing and sitting positions. Kinematic analysis provides an objective and quantitative link to clinical data (BFM scale). It is frequently used to assess the effectiveness of treatments on gait in parkinsonian patients [6], but only rarely to evaluate the effects of DBS in hyperkinetic syndromes such as dystonia [1, 5]. Some genetic forms of generalized dystonia are improved considerably by GPi stimulation for a longer period (DYT1, DYT6 or DYT11) than in our patient [2, 3], so the response of generalized dystonia to surgery in the context of SCA3 appears to be less effective and more transitory. This difference in the * Dominique Guehl [email protected]