Subthalamic nucleus deep brain stimulation for Parkinson’s disease

Scenario

A 65-year-old woman is referred to discuss deep brain stimulation surgery for Parkinson's disease (PD). She was diagnosed with PD at age 55, after presenting with dragging of the right side of her body. In retrospect, she reported some “slowness” of gait 2 years prior and had seen a number of physicians prior to the diagnosis being made. She does not report a history of tremor. After the diagnosis of PD was made, she was started on carbidopa-levodopa by her treating neurologist with excellent results for a number of years, but upon presentation, now her disease had progressed to the point where she was requiring dosing every 3 hours to maintain her best functional state. While at her best “on” condition, she reported that she felt “almost normal”—however, she reported inconsistency in medication effect, along with occasional dose failures and dyskinesias both at peak dose and end dose which could be quite violent.

• Variation : What if the patient was tremor-predominant instead of an akinetic-rigid fluctuator? -- The patient described here represents a common phenotype of patients referred for surgery, i.e., a patient who continues to obtain good benefit from medication but now experiences motor fluctuations and side effects such as dyskinesias, limiting the amount of good “on” time. In these patients, the effect of deep brain stimulation (DBS) is usually as good, but not better than their best “on” condition, but will result in fewer fluctuations, fewer dyskinesias, and possibly a need for less medication intake. Another subset of patients is those who are tremor-predominant. In those patients, the effects of DBS on tremor can be better than the best medication outcome, and surgery is usually recommended earlier in the course of the disease.

• Variation : What if the patient had rapid-onset symmetric symptomatology? -- Idiopathic PD is usually asymmetric, with an initial indolent course and a so-called “honeymoon period” over the first few years after diagnosis and pharmacologic therapy. A rapidly progressive, symmetric presentation raises concern for other conditions including but not limited to multiple systems atrophy and progressive supranuclear palsy, conditions for which DBS is not recommended as there is no evidence of long-term benefit.

• Variation : What if the patient is inadequately medicated or refusing to take appropriate dosing? -- All DBS candidates for PD should be evaluated by a neurologist specializing in movement disorders to confirm the diagnosis and whether adequate medication trials have been performed before considering surgery. If a patient has not had an adequate course of medical therapy, DBS is not usually recommended as they may respond quite well to pharmacologic therapy for many years. An exception to this may be the aforementioned tremor-predominant patient, where medication may not be as effective for tremors as DBS will be.