Functional surgery for movement disorders can significantly alleviate the motor symptoms associated with these disorders and improve the quality of life for patients with disabling diseases such as Parkinson's disease (PD), essential tremor (ET), and dystonia in appropriately selected patients. The surgical approach to movement disorders has evolved dramatically from the pre-L-dopa era to the development of modern magnetic resonance imaging (MRI)-based stereotaxic and neurophysiologic guided targeting. Current stereotactic approaches have benefited from the concurrent growth in our understanding of the functional organization of target structures and the pathophysiological basis underlying the development of these disorders. The resurgence of ablative therapy in the 1990s has given way to the development of chronic electrical stimulation of deep brain structures, that is, deep brain stimulation (DBS). DBS has given us the ability to explore surgical therapies for neurological disorders not previously approachable through ablative therapy, given the reversibility of side effects and the ability to modify stimulation parameters to optimize results.
Although an effective treatment for the motor symptoms associated with PD, over time medical treatment with L-dopa leads to motor fluctuations and drug-induced dyskinesias, side effects that compromise efficacy and diminish quality of life. Even with advances in molecular- and genetic-based therapies on the horizon, it seems likely that there will be, for the foreseeable future, a large population of patients significantly burdened by these neurodegenerative diseases who are candidates for DBS.
While many patients with ET have mild symptoms that may be controlled with medication, others are refractory to or develop a tolerance to medication, have significant disability as the tremor becomes more severe, and are often unable to perform simple activities of daily living or maintain employment.
Dystonia is a particularly disabling condition that is difficult to treat with medical therapy requiring large doses of anticholinergic medications alone or in combination with other medications such as baclofen, clonazepam, or the dopamine-depleting drug tetrabenazine. While some patients may get adequate benefit from this combination of medications alone or in conjunction with botulinum toxin injections, many require such large doses that side effects compromise the patient's quality of life. Although many patients with focal dystonias may respond to botulinum toxin alone, some of these patients will develop antibodies to the toxin and lose benefit, while others with more diffuse involvement or involvement of larger muscle groups are not candidates for botulinum therapy.
Thus there is a need for a therapy that can provide relief from the symptoms of these disorders when medical therapy is no longer effective. With the advent of DBS, a therapy is now available for these patients. As data from larger controlled clinical trials become available, neurologists and neurosurgeons will be better able to tailor therapy for individual patients through the appropriate choice of target site and mode of treatment (ablative or stimulation) that best fits the patient's disease characteristics.
The history of stereotaxic surgery for the ...