Deep Brain Stimulation (DBS)
DBS of the internal segment of the globus pallidus is increasingly used in the treatment of medically refractory dystonias, including primary generalized dystonias, and focal or segmental dystonias that do not respond to less invasive methods.[12-14] The use of DBS is supported by two placebo-controlled clinical trials,[15, 16] and multiple open, non-blinded series from different centers. Improvements vary widely from nil to nearly complete. Two independent and double-blinded trials encompassing a total of 62 patients with primary generalized or segmental dystonia showed average improvements on both the dystonia and disability subscales of the Fahn-Marsden rating scale to be approximately 50% at 3 months. The most significant complications include approximately 1% chance of stroke, immediate or delayed infection of hardware requiring its removal, mood or cognitive change, weakness, and dysphagia. These benefits can be life altering, but candidates must be advised regarding risks and potential for varying outcomes.
Based on early experience, some providers have concluded that primary generalized dystonias respond better than secondary dystonias to DBS. However, more recent studies have revealed this conclusion to be an overgeneralization. Excellent responses are regularly seen in some secondary dystonias, such as tardive dystonia, while consistently poor responses are seen in some others. Consultation with providers with broad experience is needed before recommending DBS for secondary dystonias.
Pallidotomy and thalamotomy have been used for decades in the treatment of different forms of dystonia, including focal task-specific, segmental, and generalized dystonias. Ablative procedures have been supplanted by DBS, since the latter is reversible and adjustable. Nevertheless, the ablative procedures may still be considered when implantation or maintenance of DBS hardware is not feasible or desired. The most significant complications of ablative procedures include stroke, infection, weakness, and dysphagia.
Various procedures have been used for denervating overactive muscles in cervical dystonia. Patient selection is critical, since certain subpopulations have a better outcome than others. Experienced centers have reported good outcomes for 68-89% of patients. These procedures were used more commonly before the availability of BTX therapy, so they now are reserved primarily for patients who do not respond to chemodenervation. The most significant complications include permanent muscle weakness, cosmetic effects of muscle atrophy, dysesthesia, and dysphagia.
The surgical removal of muscle tissue once was commonly offered to patients with dystonia prior to the introduction of BTX therapy. Myectomy is rarely performed nowadays, although it is sometimes still used for blepharospasm and other medically refractory dystonias as a palliative measure.
Some patients experience significant improvements after chronic intrathecal delivery of baclofen.[18, 19] Patients with leg dystonia seem to have the best responses, particularly if there is concomitant spasticity. Implanted pumps must be refilled regularly and sometimes replaced. Complications may include equipment infection or malfunction, CSF leaks, overdose, and severe withdrawal reactions. This procedure has not gained widespread popularity because of inconsistent responses among different patients, maintenance requirements, risk of severe side effects from sudden medication discontinuation from pump failure, and increasing application of DBS.
H. A. Jinnah, MD PhD
Emory University School of Medicine
Atlanta, GA 30307