In determining whether a patient is a good candidate for surgery, most surgical centers look for the following, apart from a diagnosis of Parkinson’s disease:
- Intact intellectual function and memory. Dementia (significantly impaired memory or thinking) is a major contraindication to surgery, since such patients have great difficulty tolerating the surgery, may have further loss of intellectual function due to the surgery, deal poorly with the complexity of DBS therapy, and realize little overall functional benefit.
- History of significant benefit from taking levodopa (Sinemet). Good mobility, with the ability to walk, in the best "on-medication" state is important for a good outcome. In general, surgery makes the "off" medication state more like the "on" state but rarely does better than the best "on" state, so a patient with poor function in best "on" (for example, unable to walk at any time) is a poor surgical candidate.
- Certainty of diagnosis. A number of neurological illnesses can mimic the symptoms of Parkinson's disease but do not respond significantly to levodopa. Such illnesses are often called "atypical parkinsonism" or "Parkinson's plus syndromes." These illnesses are different from classic Parkinson's disease, and they do not respond to DBS surgery. If there is a strong possibility that the patient has atypical parkinsonism rather than classic Parkinson's disease, surgery should not be performed.
- Lack of other untreated or inadequately treated illnesses. Serious cardiac disease, uncontrolled hypertension, or any major other chronic systemic illness increases the risk and decreases the benefit of surgery.
- Realistic expectations. People who expect a sudden miracle are disappointed with the results, and they may have difficulty with the complexity of the therapy.
- Patient age. The benefits of DBS for PD decline with advancing age, and the risks go up. We rarely offer surgery to a person over 80 and would only consider it if they are in otherwise excellent health, are cognitively intact, and have good function in the “on” state. For patients over 75, the benefits are likely to be modest.
- MRI of the brain should be free of severe vascular disease, extensive atrophy, or signs of atypical parkinsonism.
- Degree of disability. DBS is a poor procedure to rescue someone with end stage Parkinson's disease who is wheelchair bound or in a nursing home, although these are the most desperate patients. It is an excellent procedure for Parkinson's patients who are still employed but may be just at the point where disability would stop them from working.
- Ability to remain calm and cooperative during an awake neurosurgical procedure lasting 2-3 hours per brain side.