Conversation with … Dr. Mahlon R. DeLong

Emory neurologist discusses ‘breakthroughs’ in Parkinson’s research

Emory neurologist Mahlon R. DeLong has a lot to show for his three decades studying Parkinson’s, a progressive disease of the nervous system. His discoveries, coupled with those of French neurologist Alim Louis Benabid, have led to the current standard therapy for treating advanced stages of Parkinson’s. The treatment is called high frequency deep brain stimulation, or DBS. In September, DeLong and Benabid were honored with the prestigious Lasker-DeBakey Clinical Medical Research Award for enhancing “the lives of more than 100,000 patients worldwide.” DeLong talked about the breakthrough treatment and how it is being adapted to help people with other medical problems.

Q: What exactly is Parkinson’s?

A: Most people think of Parkinson’s in terms of tremor and slowness of movement. The hallmark of the disease is the loss of dopamine, a key neurotransmitter in the brain. Dopamine replacement, when introduced, was found to dramatically reverse the features of Parkinson’s, but as years passed, its use was complicated by troublesome side effects, including involuntary movements.

Q: Who gets Parkinson’s and why?

A: Most people develop the disease in their 60s and 70s, but it can occur earlier, particularly in hereditary forms. For 80 to 90 percent of people, it occurs without any explanation. We know there are environmental factors such as agricultural pesticides that seem to play a role. Although we don’t know the cause in most cases, both genetic and environmental factors are believed to play a role.

Q: After actor Robin Williams killed himself, it was revealed that he had Parkinson’s. Does the disease cause depression?

A: Depression and anxiety are common and can occur at any time — before, at the time of or after onset. The good thing is that these problems are treatable.

Q: How did you become so interested in Parkinson’s?

A: My research has been focused on the basil ganglia, which are brain structures involved with movement and movement disorders. Using an animal model of Parkinson’s, we were able to show that when we inactivated a specific portion of the basal ganglia, it abolished tremor and slowness of movement. Dr. Benadid then showed that it was possible to achieve the same benefit by applying high-frequency deep electrical stimulation of the same structure.

Q: How does the stimulation work?

A: It works, in part, very much like a cardiac pacemaker. People with Parkinson’s have a device implanted just below the clavicle with leads connected to electrodes implanted into specific targets in the brain. We adjust the frequency, amplitude and pulse width externally to reduce the symptoms and restore function. We do not know exactly how it works but know that it eliminates abnormal activity in specific brain networks.

Q: Can this treatment be applied to other disorders?

A: Although deep brain stimulation was first introduced for treating tremor, targeting a different part of the brain has been found useful for a variety of other neurologic disorders such as dystonia, which involves involuntary contractions of the muscles. The treatment is being explored for Tourette syndrome, epilepsy and Alzheimer’s. Psychiatric disorders such as obsessive-compulsive disorder and severe depression also are being studied.

Q: Why do you think you and your colleagues have been so successful with your research?

A: I always think so-called “breakthroughs” most often come not out of the blue, but rather, after a lot of basic research, which creates opportunity. But it is always unpredictable when something is going to turn out to have clinical relevance or value. I think we were very fortunate.