Wired Science

Deep Brain Stimulation might soon Treat a Number of Brain Disorders

When something goes even slightly wrong in the brain, a lot of bad things can happen—take depression, obsessive-compulsive disorder, chronic pain, Parkinson's disease and epilepsy, to name but a few. If only doctors had safe, reversible treatments to target the abnormal brain regions and return activity to normal. As we report in our WIRED SCIENCE segment, we already have such a solution for Parkinson's and essential tremor—it's called deep brain stimulation (DBS). What if DBS could treat these other disorders too?

In the past decade, brain imaging techniques like functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) have given scientists the ability to peek inside patients' brains and observe what goes wrong and precisely where. This represents a huge technological leap for neuroscience and psychiatry; doctors can use this information to develop next-generation treatments that specifically target affected brain regions, a big step up from drugs that bathe the entire brain and come with nasty side effects. DBS, a procedure in which doctors surgically implant a small electrode into a specific part of the brain to regulate abnormal activity, is one such next-generation solution. And doctors are currently testing it as a potential treatment for a number of diverse disorders.

Take, for instance, epilepsy. "Almost one percent of the population has epilepsy and 30 percent of those are not adequately treated with medication," explains Martha Morrell, a neurologist at Stanford University. Epileptic seizures are caused by a sudden increase in electrical activity in one part of brain that then spreads to other areas, leading to convulsions and loss of consciousness. Drugs for epilepsy aren't ideal—many patients are on a cocktail of two to three different medications, and not only are these sometimes ineffective, but they also quiet activity across the entire brain rather than just within affected regions. Patients "have a hard time concentrating, they have a hard time remembering things, they have a hard time staying focused, because of these drugs," says Michael Kaplitt, a neurosurgeon at Weill Cornell Medical Center in New York City.

As a result of these limitations, doctors are looking to DBS as a potential epilepsy treatment. A large multicenter U.S. trial testing a DBS device developed by medical technology company Medronic has recently been completed. Although epileptic seizures originate in different parts of the brain, they typically end up passing through one particular circuit as they spread. By targeting this circuit with DBS, doctors can disrupt ongoing seizures and prevent them from going further. "Patients might feel the beginning of a seizure, they might sense something's about to happen, but then it doesn't develop into a full-blown seizure," Kaplitt says.

Results from Medtronic's trial should be announced within the next few months. "If the data is encouraging, the hope is that this will be satisfactory to convince the FDA for approval," Kaplitt says. In addition, NeuroPace, a company based in California, is testing its stimulation device—which differs from Medtronic's in that it only sends impulses during seizures rather than all the time—in 28 centers around the country, according to Morrell.

Patients with treatment-resistant depression may also benefit from DBS within the next several years. "Pilot studies have reported quite dramatic things," says Kaplitt. DBS surgeries for depression require the patient to be awake so that doctors can ensure they are putting the electrode in the correct place. During some procedures, "when they got the electrode in the right spot, even on the operating table," says Kaplitt, patients "suddenly started laughing, and reported feeling like a shade was lifted off of them." That said, DBS won't be a panacea for depression, he says. "There's going to be a lot of work involved in getting the settings right and choosing the patients properly."

What about chronic pain? When we hurt ourselves by, say, bumping into a table, we often instinctively rub the affected area, and there's a reason for that, Kaplitt says: It activates sensory fibers that replace the feeling of pain with a rubbing sensation. In a similar way, DBS can be used to replace chronic pain with another feeling, like tingling. Although DBS has been used experimentally to treat chronic pain for 40 years, it's unlikely to get officially approved by the FDA because there aren't a lot of treatment candidates—it's often easier to stimulate the spinal cord directly rather than the brain, Kaplitt says.

Finally, some doctors are looking into treating Tourette's syndrome and obsessive-compulsive disorder with DBS. These diseases, however, come with a handful of challenges. It's difficult, for example, to diagnose Tourette's accurately; it's also hard to treat obsessive-compulsive patients with something like DBS, because if it doesn't work, patients begin obsessing about the implant, Kaplitt says. If doctors can overcome these challenges, however, DBS might one day be approved as a second- or third-line treatment for these disorders.

What's perhaps most fascinating about DBS is that, despite being such a success story, doctors still don't know exactly how it works. The treatment is thought to regulate brain activity by calming overactive neurons, but it could instead be that DBS changes how neurons fire, Kaplitt notes. Despite its continued mystery, the fact remains that DBS is effective, reversible (in that it doesn't permanently alter brain function) and free of serious side effects, so doctors are hopeful it could revolutionize brain medicine. After all, as Kaplitt points out, "We're not exactly sure how aspirin does everything it does to treat pain, but we still use it."