NEW YORK (Reuters Health) – Deep brain stimulation works well not only for Parkinson’s disease (PD) but also for benign tremulous parkinsonism (BTP) and the effects are long-lasting, according to papers published this week in Archives of Neurology.

In one paper, Dr. Elena Moro, from the Movement Disorders Centre, Toronto Western Hospital, Ontario, Canada and colleagues report evidence that the easing of PD motor symptoms achieved with deep brain stimulation of the subthalamic nucleus (STN-DBS) are apt to last for at least 10 years. Their analysis involved 18 patients who received bilateral STN-DBS implants between 1996 and 2000.

“To date, studies with postoperative follow-up for longer than 8 years are lacking,” the researchers note.

Another unique aspect to the study is that it’s “the first time that the clinical benefit was assessed by an independent rater blinded to patients’ clinical condition, when they were examined with or without stimulation at 10-year follow-up,” Dr. Moro noted in an email to Reuters Health.

The main outcome was the change in Unified Parkinson’s Disease Rating Scale (UPDRS) scores and subscores between the no medication/stimulation condition versus the no medication/no stimulation condition at 10 years.

“Remarkably,” said Dr. Moro, “when assessing other clinical parameters such as activities of daily living, motor fluctuations, and levodopa-induced dyskinesia, STN-DBS alone significantly improved the scores at 10 years compared to the preoperative scores without medication.”

Part of the initial benefit did wear off over time, the researchers report, mainly because of the progressive nature of PD.

STN-DBS is a symptomatic treatment for PD, “not a cure,” Dr. Moro commented. “PD progresses over time, as shown by the worsening of the axial signs (gait, balance and speech). Neither stimulator nor medication could significantly compensate for the deterioration of the axial signs at 10 years after surgery,” she said.

The researchers hope their 10-year outcome data will aid clinicians in counseling patients considering STN-DBS therapy. “It is very important to know that this surgery works also in the long-term (at least up to 10 years after surgery). However, the surgery does not stop the slow progression of the disease over time,” Dr. Moro said.

DBS for BTP

The companion paper provides some of the first evidence that deep brain stimulation is effective in patients with BTP refractive to medical therapy.

“Benign tremulous parkinsonism is a condition in the phenotypic spectrum of parkinsonism but with an uncertain pathophysiologic relationship to PD,” the authors note. Tremor, which is often disabling, is the chief symptom of BTP and typically does not respond well to dopaminergic therapy.

Dr. Bryan T. Klassen and colleagues from the Mayo Clinic in Rochester, Minnesota, report a retrospective assessment of the clinical outcomes and surgical complications in 12 men and 3 women with BTP who underwent DBS.

In their cohort of 15 patients, Dr. Klassen and colleagues saw a “consistently beneficial response” to DBS targeting either the thalamic nucleus ventralis intermedius (VIM) or STN.

At last follow-up a median of 4 years after implant, 7 patients (47%) were tremor free, 6 patients (40%) had only slight tremor and 2 were considered “definitely improved but with residual tremor.”

There were no perioperative complications in any patient and no reports of cognitive impairment, mood disorder, speech disturbances or disabling postural instability after surgery.

Until now, no published series has specifically focused on the effect of DBS on BTP, Dr. Klassen and colleagues note.

They say “prospective studies with larger sample sizes and using randomized target selection are necessary to determine the relative efficacy, durability, and adverse events occurring with VIM vs STN DBS in this patient population.”

Arch Neurol 2011.