If the human brain is a subway, then the issues caused by Parkinson's and Alzheimer's are damaged tracks and broken down trains preventing neurological "commuters" from carrying their messages throughout the body.
As with any type of travel congestion, such interruptions have a snowball effect, according to Paul Larson, M.D., associate clinical professor and vice chair of neurological surgery at the University of California, San Francisco. "These disorders damage brain circuits and disrupt neural processes similar to how an out-of-commission track slows down trains and throws off the schedule of the entire subway," he says.
Depending on the disease, pharmaceuticals and physical therapy for Parkinson's disease have varying rates of success in mitigating symptoms, mainly because scientists don't fully understand the nuances of all of the neural routes that are disrupted. But some individuals may also qualify for a promising surgical option that can help smooth out the neurological bottlenecks caused by Parkinson's and other similar diseases. The procedure, called deep brain stimulation (DBS), is rapidly gaining in both popularity and proven benefit.
Deep brain stimulation explained
DBS treatment involves implanting electrodes in specific areas of a person's brain. Doctors take MRI scans of the brain prior to the procedure to determine where to place the electrodes. An impulse generator, which turns the electrodes on and off, is placed underneath the skin just below the collarbone.
Much like a pacemaker helps keep heart rhythms in check, the DBS system delivers carefully-timed electrical pulses to certain parts of the brain in order to stop the erratic neural signals that cause the physical and mental symptoms of certain diseases.
"Diseases like Parkinson's and depression are essentially circuit disorders," says Larson, who has performed multiple DBS surgeries. "With Parkinson's in particular, we've been able to study the pathology enough to know where the dysfunctional circuits are and how the flow of information is being interrupted."
A particular benefit of DBS is that, unlike some electrical treatments for neurological disorders, it does not destroy brain cells. The stimulation simply blocks the electrical signals that cause undesirable symptoms, making it both an adjustable and reversible treatment.
How effective is it?
The FDA has given the green light for DBS to be used to treat people with Parkinson's, essential tremor, dystonia and certain forms of severe obsessive-compulsive disorder.
The accidental revelation that DBS might also have potential as an Alzheimer's therapy occurred when Canadian researchers discovered that implanting electrodes near the fornix—an area of the brain associated with memory formation—appeared to increase brain activity and stave off mental decline in some people with the disease.
Additional research is currently underway to determine how helpful the surgery could be for those with the most common form of dementia. A preliminary investigation, conducted by Johns Hopkins University (JHU) researchers and involving six individuals with mild Alzheimer's, found that the treatment may improve glucose metabolism in the brain—a key indicator of mental functioning.
Though she admits her team's findings need to be duplicated on a larger scale, study author Gwenn Smith, Ph.D., a professor in the Department of Psychiatry and Behavioral Science at the JHU School of Medicine says, "We don't have another treatment for Alzheimer's dementia at present that shows such promising effects on brain function."
Important things to know about DBS for Parkinson's
DBS is a treatment, not a cure. But, particularly when it comes to Parkinson's, there are proven benefits. Research has shown that people with advanced Parkinson's who underwent DBS can have up to five more symptom-free hours per day than those on medications alone.
However, there are a few important caveats to keep in mind when considering DBS as a treatment option for Parkinson's:
- DBS is only effective in people who've responded positively to levodopa medications (Stalevo, Parcopa, Sinemet). It cannot help symptoms that aren't affected by levodopa.
- DBS alone won't alleviate all symptoms, but it can significantly decrease the amount of medication an individual must take to find relief.
- For reasons that remain unclear, DBS surgery does not work as well if a person with Parkinson's is over 80 years old.
As with any surgery, DBS carries the risk of certain complications—infection, adverse reactions to anesthesia, etc. These risks are often heightened among the elderly, so an individual's age overall health and wellbeing must also be taken into account.
Traditionally, undergoing DBS surgery meant being temporarily weaned off Parkinson's medication and remaining awake during the entire procedure--two requirements that presented uncomfortable barriers to otherwise good surgical candidates. Now however, a new real-time MRI system, called ClearPoint, enables individuals to continue taking their medications and be sedated during DBS surgery. Larson, who's been using this technique for years, says it's a much more accurate way of conducting the procedure and is more comfortable for the patient.
When a loved one has Parkinson's disease, there are key questions to ask their doctor, and Larson says it's important for anyone considering DBS to not only consult with their primary care doctor, but a neurologist as well.