Deep Brain Stimulation for Professionals
For the most severe cases of TS, Deep Brain Stimulation (DBS) may be considered after all other appropriate treatments have been considered and failed. DBS remains an experimental surgical procedure and continues to be studied as an effective treatment.
How DBS Works
The two essential components to the hardware involved in DBS are the implantable electrodes and the programmable pulse generator. The DBS electrode is implanted into a specific target within the brain, and the pulse generator, or neurostimulator, is implanted under the skin just below the collar bone (or in the abdomen for women); an extension cable passes under the skin and connects the electrode to the neurostimulator.
The DBS electrode has four contact points, the sites through which electricity is delivered. Active contacts can be selected by computer and multiple settings can be adjusted for individual patient needs. The settings can be adjusted to vary which contact points are used (how long each pulse of stimulation lasts), frequencies (how many pulses are delivered each second), and amplitudes of stimulation (how much voltage is delivered).
DBS has the potential to “neuromodulate” abnormal communication that occurs deep within the brains of people with TS. So far, researchers have probed into several areas in the brain of people with TS (the centromedian thalamus, the internal globus pallidus, the external globus pallidus, and the anterior limb of the internal capsule) and they have had mixed success. While the best target for “neuromodulation” has yet to be determined, it does appear that DBS had positive results in some patients.
DBS Requires a Multidisciplinary Approach
Successful DBS surgery usually requires a multi/interdisciplinary approach. For TS, a neurologist and psychiatrist/neuropsychiatrist experienced in TS, a neurosurgeon experienced in DBS, and a general practitioner can serve important roles. In some cases social work, physical, occupational and speech therapy may be useful. Additionally, adequate imaging must be performed both before and after DBS (usually an MRI and/or CT), and the results of each part of the screening should be discussed in a DBS team meeting/board.
Commitment is Required
DBS is a major surgery and can therefore be associated with complications. DBS requires a significant time commitment, and patients and families must be motivated and committed to undergo not only the procedure but also the challenges associated with the pre-operative workup and the significant follow-up after the procedure. The family must return for multiple evaluations and realize that the average patient may be programmed 4 to 8 times in the first six months following surgery and may need numerous medication changes.
Complications of DBS
DBS can generate short and long-term “potential” complications. The DBS device is a “foreign body” in the brain and under the skin, so infection is a primary worry, and can occur in five percent or more of implanted patients. Also, during placement of the DBS electrodes, there could be bleeding, or alternatively, a stroke that may lead to weakness, numbness, changes in vision, and/or changes in speech.
The DBS device can fracture/break, migrate out of position, or malfunction requiring another surgical procedure to replace or reposition the electrode. DBS frequently affects speech, and particularly verbal fluency. There can be worsening of cognition or mood, and in rare cases associated suicidal thoughts, which is why patients must be carefully screened and followed.
A significant risk of a DBS procedure is failure to achieve the patient’s pre-operative expectations, and this is why it is absolutely critical that both patients and physicians have focused pre-operative discussions.
Selection Criteria for Deep Brain Stimulation
Deep Brain Stimulation is FDA approved for Parkinson’s disease, essential tremor, dystonia and OCD, and currently utilized for patients who have not responded to standard medical or behavioral therapy. Patients with no cognitive difficulties or “minimal” cognitive dysfunction may be appropriate candidates.
DBS is an Experimental Therapeutic Approach
Some individuals with severe TS have already received DBS therapy and have experienced significant benefit, but many others have shown little or no improvement in symptoms. Thus, DBS remains an experimental therapeutic approach and is not currently approved by the FDA for treating TS. Probably the most crucial step for successful DBS is careful patient selection. Despite the use of DBS, there are no standardized criteria for candidate selection.
General Considerations for DBS Treatment
- The diagnosis must be made by an expert psychiatrist and/or neurologist.
- The Yale Global Tic Severity Scale should be performed and must reveal incapacitation with severe distress, self-injurious behavior, and/or quality of life disruption. OCD, depression, and ADHD are not exclusionary, provided tics are the major difficulty requiring surgical intervention.
- Must be over 25 by FDA and Tourette Association guidelines. There may be exceptional cases where younger patients are acceptable candidates for DBS surgery.
- The patient’s TS symptoms must have failed to respond to conventional therapy for tics. Specifically, subjects must have been treated by a psychiatrist or neurologist experienced in Tourette Syndrome (usually treated with at least three different pharmacological classes: an alpha-adrenergic agonist, dopamine antagonists (typical and atypical), and a benzodiazepine).
- Patients must have received stable and optimized treatment of co-occurring or other medical, neurological, and psychiatric disorders for the previous six months.
- If the patient has a tic that is focal or addressable, botulinum toxin treatment should be considered.
- If present, psychiatric disorders, such as anxiety, depression, or bipolar disorder, must be treated and stable.
- Patients must be screened for dementia or cognitive dysfunction that will place the patient at risk for worsening cognition, and/or may impact the ability to cooperate with tasks involved in the study.
- Patients should have been evaluated for the suitability, and implementation, if suitable, of behavioral interventions to reduce tic severity.