Ideal candidates for deep brain stimulation surgery to treat Parkinson's disease will generally meet the following criteria:
- Patients whose diagnosis of idiopathic Parkinson's disease is certain. Some Parkinson's disease variants, such as progressive supranuclear palsy (PSP); multiple system atrophy (MSA); Shy-Drager syndrome; striatonigral degeneration (SND); dementia with Lewy bodies; or parkinsonism due to toxins, infections, or strokes, are not responsive to deep brain stimulation.
- Patients with a robust response to carbidopa/levodopa (Sinemet) that is a 25-30% improvement in mobility with carbidopa/levodopa (Sinemet) when comparing "on" and "off" responses. The best candidates are patients who fluctuate between "on" and "off" periods throughout the day. Typically, the surgery improves the amount of "on" time rather than improving "on" time functionality.
- Patients whose symptoms are not controlled adequately by drug therapy, such as individuals on maximally tolerated doses of dopamine agonists (Mirapex, Permax, Requip), carbidopa/levodopa (Sinemet) at appropriate intervals, trials of COMT inhibitor (Comtan), and potentially use of amantadine for dyskinesias.
- Patients who are cognitively normal. Patients with dementia or significant memory disturbance that is not a medication side effect are not good candidates. In fact, surgery can permanently worsen cognition in these patients. Neuropsychological testing may be needed to determine whether patients are good candidates.
- Patients who are otherwise healthy, that is, who do not have serious cardiac, pulmonary, or other chronic illness.
- Patients who are less than 75 years old. However, patients over 80 years old who are very healthy and who exhibit good function in the "on" state may still be considered.
- Patients with satisfactory brain imaging. Severe atrophy or vascular disease on the brain MRI suggests poor tolerance of the surgery.
- Patients who can remain calm during surgery. Deep brain stimulation is done while the patient is awake and under mild sedation. Some cooperation with the surgery is required.
- Patients with realistic expectations. The surgery requires frequent monitoring and doctor visits (at least initially). Typically, Parkinson's disease medications are still required although perhaps at lower doses. In addition, the stimulator is bulky and can be felt and seen under the skin. Patients should not expect a miracle "cure."
Patients should discuss these factors with their primary neurologist. They should discuss which symptoms will respond to deep brain stimulation and stabilize, which symptoms will not respond to deep brain stimulation and will worsen with time, and which symptoms may worsen as a result of deep brain stimulation. Furthermore, it is very important for patients to meet with the team of physicians that will program the stimulator before surgery.