Careful Site Selection Required for Deep-Brain Stimulation Treatment in Patients With Parkinson's Disease

Careful Site Selection Required for Deep-Brain Stimulation Treatment in Patients With Parkinson's Disease: Presented at AD/PD

By Chris Berrie

PRAGUE, Czech Republic -- March 14, 2009 -- Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is as effective as DBS of the globus pallidus (GPi) for improvements of fine motor function in patients with idiopathic Parkinson's disease (PD) when they were on medication, researchers noted here at the 9th International Conference on Alzheimer's and Parkinson's Diseases (AD/PD). When off medication, however, these patients can experience greater long-term adverse events with STN stimulation, despite the fact that it reduces the levodopa dosing needed for symptom management.

DBS is an alternative therapy for patients with PD, and involves surgical implantation of an electronic device into the STN or the GPi, with stimulation at both sites being effective in reducing motor symptoms.

"Deep brain stimulation is typically done when pharmacologic remedies fail, and it is currently done at more of an advanced stage of disease," noted principal investigator Tracie Caller, MD, Dartmouth Hitchcock Medical Centre, Lebanon, New Hampshire, presenting a systematic review here on March 14.

With little known about which stimulation site produces better outcomes, Dr. Caller's analysis was designed to compare the efficacy and safety of DBS of the STN and the GPi for reducing fine-motor symptoms in patients with PD.

Dr. Caller and colleagues searched the MEDLINE database, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, ClinicalTrials.gov Web site, and bibliographies and meeting abstracts for relevant studies for direct comparisons of STN and GPi stimulation. They needed to report Unified PD Rating Scale (UPDRS) scores at preoperative baseline levels and at a minimum follow-up of 6 weeks. An assessment of the data quality was carried out by 2 blinded, independent reviewers.

Thirteen reviewed studies were found to be eligible according to inclusion criteria. The combined patient numbers saw DBS in the STN for 282 patients and in the GPi for 140 patients. Mean baseline characteristics were as follows: age 50 to 64 years; disease duration 8 to 17 years; and UPDRS motor scores off medication of 40 to 64.

Mean reductions in off-medicine UPDRS motor scores for the STN and GPi subjects at trial follow-up were 47% and 36%, respectively. On medication, these benefits were lower, at 14% and 20%, with 36% and 5% of subjects, respectively, showing reductions in levodopa treatments during follow-up.

The mean difference in the UPDRS motor scores across these trials thus demonstrated a significant benefit when off medication in favour of DBS in the STN over the GPi (-8.75; 95% confidence interval [CI], -13.46 to -4.04; P < .0001), although this benefit was lost when patients were on medication (1.73; -2.71 to 6.17; P = .09).

The adverse effects related to these stimulation sites were significantly higher for stimulation in the STN (risk ratio, 4.27; 95% CI, 1.17-15.52; P = .03). As the severities of these adverse effects were reported differently across the studies, however, this significant difference might not provide an accurate reflection overall of which adverse events were truly clinically significant, the researchers concluded.

"We tend to prefer subthalamic nuclear stimulation right now, clinically, but I think that with the rate of adverse effects of stimulation we need to be a little more careful in selecting who we are applying this technique to," Dr. Caller indicated.

[Presentation title: Deep Brain Stimulation of the Subthalamic Nucleus Versus Globus Pallidus for Parkinson's Disease: A Systematic Review. Abstract P2-135]