The new findings should “make patients and physicians consider the option of DBS surgery earlier in the course of Parkinson’s disease, before patients become disabled and before their work and social lives suffer too much,” noted Andres Lozano of Toronto Western Hospital, Canada, a DBS expert who was not involved in the study. However, because the analysis did not address long-term DBS risks, some clinicians said they would be reluctant to recommend the technology to early-stage PD patients.

Nobody quite understands how DBS helps the 2 to 5 percent of PD patients who opt for the procedure. Scientists think it may work by activating GABAergic inhibitory neurons, thereby normalizing a basal ganglia circuit that becomes hyperactive as dopamine neurons die off in PD, Deuschl said. Typically, patients who receive DBS have battled the disease for more than a decade and reached a point where dopamine-boosting medicines no longer relieve the worst motor symptoms. DBS candidates also tend to be younger, with no or little cognitive impairment.

In two previous six-month randomized trials, neurostimulation relieved symptoms more effectively than medical management alone in people with advanced PD and severe motor complications (Deuschl et al., 2006; ARF related news story on Weaver et al., 2009). The implants also improved symptoms and quality of life in early-stage PD, though that trial had just 20 participants (Schüpbach et al., 2007).

For the current study, first author W. Michael Schüpbach and colleagues enrolled 251 patients at 17 sites in Germany and France. The participants were on the young side (mean age 52-53 years), had had Parkinson’s for an average of 7.5 years with early signs of motor complications, and no dementia or major depression. They were randomized to receive neurostimulation of the subthalamic nucleus or medical therapy alone, with assessments at five, 12, and 24 months.

Quality of life—the trial’s main endpoint—improved by 26 percent in DBS-treated patients, but hardly changed in the control group. The researchers saw clear improvement with DBS at the five-month timepoint, and the benefit persisted. “There was no worsening of life quality across two years,” Deuschl said. Neurostimulation also improved daily function and mobility, and relieved complications from dopaminergic drugs.

“This study is especially important because it demonstrates that DBS can be used earlier in the course of Parkinson’s disease, rather than saving it as a last resort,” wrote Kenneth Follett, University of Nebraska Medical Center, Omaha, in an e-mail to Alzforum. Jerrold Vitek of University of Minnesota School of Medicine, Minneapolis, agreed, calling this “an impact paper that makes people think about [using DBS] earlier.” For patients who start developing complications with medications, DBS would improve quality of life, he said.

Frances Weaver of Hines Veterans Affairs Hospital, Illinois, found the data compelling, but wondered if they apply to the bulk of PD patients, who tend to be older. Based on their disease duration and average age at baseline, most trial participants would have been in their forties at the time of diagnosis, she noted. “I’m not sure how applicable the findings would be for PD patients diagnosed when older, which is more common,” Weaver said. Only 11 percent of PD cases are diagnosed before age 60. Moreover, 30 percent of PD patients, particularly older ones, have dementia, which would have excluded them from the current study, noted Caroline Tanner of Stanford University School of Medicine, Palo Alto California, in an accompanying editorial. The current study cannot tell if DBS would work for older PD patients, she wrote.

The study also does not address long-term DBS complications, which some see as an important consideration. The risks “associated with implantation and non-physiological electrical stimulation on diverse neural brain circuitries are not known,” noted Ole Isacson of Harvard Medical School’s McLean Hospital, Belmont, Massachusetts, in an e-mail to Alzforum (see full comment below). Furthermore, he thinks the trial is “too short to address the most important caveat—loss of DBS efficacy over time.” In prior studies looking at DBS patients five to 10 years post-surgery, patients showed sustained improvement in muscle rigidity, tremor, and dyskinesias, whereas gait and speech seemed to worsen with time (Fasano et al., 2010; Moro et al., 2010; Castrioto et al., 2011).

As with any treatment, the benefits of DBS must be weighed against cost and risk. The new data “aren’t compelling enough for me to recommend surgery to an early PD patient,” said Warren Olanow of Mount Sinai Hospital in New York. “The procedure carries risk of infarction, infection, and side effects, not to mention cost.” A DBS device costs $20,000-$30,000. The therapy can also affect a person’s mood and emotions (see Part 2 of a four-part DBS series). Nevertheless, DBS is gaining international credibility as a suitable treatment for some high-functioning PD patients (ARF related news story). The therapy is also starting to show its mettle in other disorders. The procedure looked safe in a small Phase 1 trial in people with Alzheimer’s disease (ARF related news story on Laxton et al., 2010), is currently being tested in a Phase 2 AD trial (see ARF related news story), and appears to improve functional connectivity in AD patients (ARF related news story on Smith et al., 2012). In a prospective study published this month in the journal Neurosurgery, researchers report that DBS improves quality of life in people with neuropathic pain (Boccard et al., 2013).—Esther Landhuis.

References:
Schüpbach WM, Rau J, Knudsen K, Volkmann J, Krack P, Timmermann L, Hälbig T, Hesekamp H, Navarro S, Meier N, Falk D, Mehdorn M, Paschen S, Maarouf M, Barbe MT, Fink GR, Kupsch A, Gruber D, Schneider GH, Seigneuret E, Kistner A, Chaynes P, Ory-Magne F, Courbon CB, Vesper J, Schnitzler A, Wojtecki L, Houeto JL, Bataille B, Maltete D, Damier P, Raoul S, Sixel-Doering F, Hellwig D, Gharabaghi A, Krüger R, Pinsker MO, Amtage F, Regis JM, Witjas T, Thobois S, Mertens P, Kloss M, Hartmann A, Oertel WH, Post B, Speelman H, Agid Y, Schade-Brittinger C, Deuschl G for the EARLYSTIM Study Group. Neurostimulation for Parkinson's Disease with Early Motor Complications. N Engl J Med. 14 Feb 2013. Abstract

Tanner CM. A Second Honeymoon for Parkinson’s Disease? N Engl J Med. 14 Feb 2013. Abstract