Nucleus ventralis oralis deep brain stimulation in postanoxic dystonia.

Deep brain stimulation (DBS) of the thalamus, zona incerta, subthalamic nucleus, and pallidum has been used for the treatment of dystonia. Reports on thalamic DBS for dystonia were published as early as 1977. Thalamic stimulation may increase the dystonic symptoms, especially when the Vim nucleus is the target of the stimulation. However, targeting the thalamus was abandoned because several publications suggested that the globus pallidus internus (GPi) is a better choice for stereotaxy in patients with dystonia. An interesting issue is what happens in case of a structural lesion in the GPi? Structural lesions of the GPi are not considered an absolute contraindication for the DBS electrode placement; however, thalamic nuclei could be an alternative target. We describe the case of a female hemidystonic patient with bilateral structural abnormalities of the GPi, due to postanoxic damage, who was treated successfully with DBS of ventralis oralis anterior (Voa) nucleus. A 37-year-old woman presented with a right side hemidystonia. There was no family history of dystonic conditions. The pregnancy was normal and the delivery was spontaneous at term, but complicated by prolonged labor and insufficient blood supply from the umbilical artery. The perinatal adaptation and motor development were normal. At the age of 3, she started to develop a right lower limb dystonia that led to walking impairment. Hemidystonia developed progressively, and within years walking became impossible. The patient was wheelchair bound and required assistance in dressing and hygiene, for the last 9 years (Video 1). The neurological examination revealed a dystonic posture of the right side of her body, with the lower limb more severely affected. The right hand was kept periodically in a hyper flexed claw-like fashion, and the foot exhibited permanent dorsiflexion and extortion. She had normal power of all muscle groups on the affected right side. The tendon reflexes were symmetrical, and no pathological reflexes were present. The neurological examination of the left side of the body was normal. Her vital signs and general physical examination were unremarkable. The laboratory tests, including cooper level and ceruloplasmin, were within normal limits. Preoperative magnetic resonance imaging (MRI) showed bilateral postanoxic lesions in the globus pallidus (Fig. 1). The GPi was totally damaged bilaterally. Several medications (L-dopa, tizarnidine, baclofen, tetrabenazine) had been unsuccessful in improving the patient’s symptoms. Dystonia was videotaped and assessed using the Burke, Fahn, Marsden Dystonia rating scale (BFMDRS) preoperatively and postoperatively at monthly intervals for the first year and at 3-month intervals thereafter. The patient underwent a stereotactic implantation of an electrode (model 3387, Medtronic, Minneapolis, MN) in the left nucleus Voa. The correct position of the electrode was evaluated postoperatively by MRI scan and the Frame-Link software. The final electrode position was at the base of the Voa nucleus close to the Voa/Vop border. The active contacts of the electrode were the contacts 0 and 1 inside the Voa nucleus (Fig. 2). The initial postoperative stimulation parameters were 2.5 volts, 185 Hz, 250 lsec, with monopolar stimulation on contacts 0 and 1, respectively. Further adjustments of the stimulation parameters were performed during the follow-up period. The amplitude ranged between 2.5 and 3.6 volts, pulse width ranged between 250 and 450 lsec while the frequency was kept stable at 185 Hz. The functional status and the daily life activities were gradually improved after 6 months postoperatively, having the best results on the 12 month follow-up assessment. The good outcome lasts up today (28 months postoperatively). The BFM dystonia scale improved by 76% in total (disability scale improved from 13/30 to 6/30 and movement scale improved from 20/120 to 2/120). The patient is now able to walk again after 9 years use of a wheelchair with the stimulator always on function (Video 2). She still suffers intermittently, under stress conditions, from minor jerky movements of the right hand, but the movements of the right upper limb are less prominent compared with the preoperative condition.