Globus Pallidus Deep Brain Stimulation for Dystonia
Abstract & commentary
Source: Kumar R, et al. Globus pallidus deep brain stimulation for generalized dystonia: Clinical and PET investigation. Neurology 1999;53:871-874.
The current treatment of dystonia includes pharmacotherapy (principally treatment with anticholinergics, baclofen, and clonazepam) and botulinum toxin injections. While they are often effective, many patients with dystonia obtain little to no relief from these approaches. Kumar and colleagues report their encouraging experience with bilateral pallidal deep brain stimulation in a patient with idiopathic generalized dystonia.
At the age of 32, their patient developed symptoms of dystonia, which gradually worsened despite treatment with conventional medical therapy and botulinum toxin injections. Genetic testing was not performed and there was no family history of dystonia or neuroleptic exposure. At the age of 49, she was completely disabled and unable to work. Her dystonia was generalized, involving the face, neck, arms, feet, and trunk.
She underwent bilateral same-sitting implantation of internal globus pallidus stimulators under microelectrode guidance. After determination of the optimum settings of the implanted pulse generators, double-blind patient examinations revealed marked immediate bilateral improvement in her dystonia. Dystonic symptoms improved by 65%, as measured by the standard clinical rating scale for dystonia, the Burke-Fahn-Marsden scale. Unilateral stimulation of the right GPi improved contralateral limb posturing and left truncal tilt. Unilateral stimulation of the left GPi improved facial dystonia and blepharospasm. The effects of bilateral stimulation were additive.
One year after electrode implantation, the patient underwent (15O)H20 PET scanning. This technique measures changes in cerebral blood flow, and, by inference, cerebral cortical activation. Prior studies have shown that primary and association motor cortices are excessively activated by such maneuvers in patients with dystonia. Scans taken in this patient during performance with the joystick showed suppression of abnormal activation of motor and supplemental motor areas, i.e., restoration of the normal pattern of cortical activation during movement.
The beneficial effects of stimulation were maintained for more than one year. However, hardware malfunction on one side and contralateral erosion of the scalp over the other electrode required removal of both stimulators and loss of therapeutic benefit.
Commentary
Several features of this paper merit comment. Four decades ago, Irving Cooper opened the field of stereotaxic surgery for dystonia by performing cryothalamotomies on patients with generalized dystonia. While his patients often experienced dramatic intraoperative benefit, these results were often short-lived. Bilateral thalamotomies produced severe speech disturbances in more than 25% of patients, and this approach soon fell out of favor. With the resurgence of interest in pallidal surgery for Parkinson’s disease, there has been growing interest in pallidal surgery for patients with intractable dystonia.
Experience with pallidotomy and pallidal stimulation for dystonia is limited, with fewer than 100 patients reported in the literature. Several critical questions remain to be answered. The most important issue is the selection of appropriate candidates for the procedure. Given the inherent risks of deep brain surgery, only patients with intractable generalized dystonia should be considered for this procedure. Patients with DYT-1 dystonia (Oppenheim’s dystonia) probably do better with these procedures than patients with secondary dystonia. Results of pallidotomy in patients with secondary dystonia have been disappointing. While immediate improvement was seen with stimulation in this report, several patients with DYT-1 dystonia have enjoyed delayed improvement after bilateral single-sitting pallidotomy. These patients continued to improve for weeks to months after the procedure, suggesting more permanent changes in cortical connectivity.
Finally, the question remains whether pallidotomy or pallidal stimulation is preferable for these patients. Pallidal stimulation offers several advantages; bilateral procedures can be performed without undue risk of neurobehavioral catastrophes, and stimulation parameters can be optimized to produce the maximum clinical benefit. The drawbacks of stimulation were evidenced in this patient-hardware failure and erosion of the scalp lead, requiring removal of the devices. —sf (Dr. Steven Frucht is Assistant Professor of Neurology, Movement Disorders Division, Columbia-Presbyterian Medical Center.)
Which one of the following statements regarding deep brain stimulation for dystonia is true?
a. Deep brain stimulation of the globus pallidus improves blepharospasm and torticollis but does not improve truncal dystonia.
b. The effect of the deep brain stimulator is maximal immediately after implantation.
c. Deep brain stimulation of the globus pallidus increases activation of the motor and supplementary motor cortex when the patient performs a motor task.
d. The surgical risk of hemmorhage, stroke, or blindness from implantation of a stimulator is 1-2%.
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content