Deep Brain Stimulation for Parkinson’s & Pain

THIS IS GOING TO SOUND LIKE SOMETHING OUT OF A SCI-FI MOVIE.

Deep brain stimulation (DBS)—used most commonly to treat advanced Parkinson’s disease and essential tremor but also for obsessive-compulsive disorder (OCD), dystonia, pain and, recently, depression—is brain surgery performed while the patient is awake. And it begins with a hole drilled into the patient’s skull.

But it’s a lot less terrifying than it sounds.

The scalp is numbed, so the patient feels no pain. Also, the hole that’s drilled is the size of a piece of spaghetti, says Nicholas Boulis, MD, a Harvard-trained neurosurgeon at Emory Healthcare in Atlanta. Besides, he explains, “You’re awake, but your brain is put to sleep.” The neurosurgeon needs to communicate with the patient during the meticulous, one-to-three-hour brain “mapping” procedure—the first in a two-step process.

Dr. Boulis’ description makes the procedure sound like cartography: “We use imaging with atlases of the brain structure.” He talks about “known landmarks” of the brain: “We map the area. And then we listen for activity. We stimulate parts of the brain [with tiny electrodes] and look for a response.

“Basically, we’re taking a system that’s out of balance and rebalancing it,” Dr. Boulis explains.

WHO’S A CANDIDATE?

Not everyone with Parkinson’s or tremor is a good candidate for DBS, which has been FDA approved for Parkinson’s since 1997. “Patient selection is very important,” Dr. Boulis says. “We look for patients with symptoms that will respond.”

There’s an open debate among doctors now about when the best time is to perform DBS in a Parkinson’s patient—early in the disease’s progression toward off some of its effects? Or later, after the symptoms are noticeable and more troublesome?

“I’d rather do the surgery when the patient is healthy,” says Dr. Boulis. But the counterargument is that if there are complications, the patient has to live with them longer.

Some people who develop tremors and rely on their hands for work—pilots, photographers and other craftspeople—may request DBS surgery early to prolong their careers.

“The general rule of thumb is that if you can avoid brain surgery, you should,” Dr. Boulis says. He makes sure his patients understand the benefits and risks before they make a decision. “There is a 1 percent chance of having something resembling a stroke during this procedure,” he says. Potential patients have to take that into consideration.

Ali R. Rezai, MD, is director of the Neurological Institute, associate dean of neuroscience and Stanley and Jodi Ross Chair in Neuromodulation at The Ohio State University. He points to the “30-year track record of safety” DBS has in the United States, even as he acknowledges that brain surgery is never anyone’s first option. He, too notes the unlikely but serious risks involved—a 1 percent chance of bleeding in the brain, a 2 percent chance of infection and a 2 percent chance of device malfunction.

Dr. Rezai says his typical DBS patient is someone with Parkinson’s who’s been on medication for about five years and for whom medication has stopped being effective. The tremors aren’t responding to meds, and the patient is having more and more difficulty getting around. If there are no major heart or lung problems, this typical patient may be a good candidate for DBS.

MAPPING THE BRAIN

Many steps lead to mapping the brain. Dr. Boulis describes the major ones:

• Prepare and numb part of the scalp and drape it off.
• Place fiducials on the patient. (Dr. Boulis says this contraption looks something like a birdcage mounted on the patient’s head. It’s there as a marker or point of reference.)
• Identify the right brain target (or targets) and the right trajectory.
• Ensure the hole in the skull allows for the safest trajectory. (Boulis says the hole alone can often cause relief.)
• After all of the above takes place, the surgeon turns the power over to the neurologist in the OR who tries to hit the target(s) in the brain causing the tremors. This may take repeated attempts.

During the mapping phase, the patient remains awake. But for the second part of the procedure—when electrodes are implanted in the brain—the patient is under general anesthesia.

DBS uses electrical impulses to stimulate a target area in the brain. The stimulation affects movement by altering the activity in that area, and the stimulation can be changed or stopped at any time. The DBS system, once fully implanted, has three parts:

1. the implanted pulse generator (IPG), a battery-powered gizmo that sends electrical pulses to the brain to trick it into not producing tremors 2. the lead, a coiled wire with electrodes that’s placed in one or two different nuclei of the brain
2. the extension, which connects the IPG to the lead (It’s an insulated wire that runs below the skin, from the head to behind the ear to the IPG.)

“We bury the tail of the electrode under the scalp,” Dr. Boulis says. “And then we ‘un-bury’ it a week or so later.” During the second procedure, a small battery-powered device—the IPG, which is similar to a pacemaker—is implanted in the chest and connected, by a wire, to the electrodes in the brain.

The device can be programmed to deliver the right level of stimulation for the greatest relief of symptoms. Doctors don’t program the implantable device until weeks after it’s been implanted. The brain has to recover from surgery before that can happen. After that, a patient may come back to the doctor every couple of months for programming.

FEELING RESULTS

DBS involves a big, complex series of operations. But the results can be equally big. In a patient with advanced Parkinson’s, symptoms will likely improve almost immediately after the surgery, Dr. Rezai says. In fact, there’s a greater than 75 percent chance the tremors will resolve. Other Parkinson’s symptoms will improve, too.

Rigidity—or the resistance to passive motion common in Parkinson’s patients—will also likely improve, Dr. Boulis says. Patients will need to take fewer meds. “DBS increases the part of your day when you’re at your best,” he says.

Still, Dr. Rezai notes: “This is a life-enhancing surgery; it’s not a life-saving surgery.”

Dr. Boulis agrees: “DBS doesn’t stop the nerve damage that Parkinson’s can create. Parkinson’s can still progress, and the patient can develop other symptoms.” Still, the patient’s quality of life has been improved because the tremors have been halted or diminished.

And the Michael J. Fox Foundation for Parkinson’s Research—one of the leading sources for research and information on the disease—offers a practical assessment of the benefits (and limitations) of DBS. The site also offers hope that more and more people may be able to benefit from DBS: “Advances in the understanding of DBS mechanisms and improvements in the devices and surgical approaches may eventually make the therapy effective for more symptoms and, as a result, for a wider variety of people at different stages of Parkinson’s.”

DBS is not FDA approved to treat chronic pain, so insurance won’t cover it for that condition. Dr. Rezai says the procedure has been performed “off-label” or for research purposes in chronic pain patients, but it doesn’t have the same success rates it does for Parkinson’s. About 40 percent of chronic pain patients see improvements in their condition after DBS.

But for patients with tremor, DBS may be just what the doctor ordered. As Dr. Rezai says, “It’s an option for people who feel they’ve run out of options.”

PARKINSON’S & PAIN
IS PARKINSON’S DISEASE PAINFUL?

Special thanks to the contributions of Blair Ford, MD, Center for Parkinson’s Disease & Other Movement Disorders, Columbia University Medical Center.

Descriptions of Parkinson’s do not generally include the mention of pain. And yet, when carefully questioned, more than half of all people with Parkinson’s disease say they have experienced painful symptoms and various forms of physical discomfort. Most people experience aching, stiffness, numbness and tingling at some point in the course of the illness. For a few of them, pain and discomfort are so severe that they overshadow the other problems caused by the disease. Pain syndromes and discomfort in Parkinson’s usually arise from one of five causes: (1) a musculoskeletal problem related to poor posture, awkward mechanical function or physical wear and tear; (2) nerve or root pain, often related to neck or back arthritis; (3) pain from dystonia, the sustained twisting or posturing of a muscle group or body part; (4) discomfort due to extreme restlessness; and (5) a rare pain syndrome known as “primary” or “central” pain, arising from the brain.

It takes diagnostic skill and clinical experience to determine the cause of pain in someone with PD. The most important diagnostic tool is the patient’s history. Where is the pain? What does it feel like? Does it radiate? When does it occur during the day? Does it occur in relation to any particular activity or medication? Perhaps the most important task for people with Parkinson’s who experience pain is to describe as accurately as they can whether their medications induce, aggravate or relieve their pain.

Musculoskeletal Pain

Aching muscles and joints are especially common in PD. Rigidity, lack of spontaneous movement, abnormalities of posture and awkward mechanical stresses all contribute to musculoskeletal pain in PD. One of the most common musculoskeletal complaints is shoulder stiffness, sometimes called a frozen shoulder (this may, in fact, be the first sign of PD). Hip pain, back pain and neck pain are all common complaints in PD. With prolonged immobility of a limb, band-like tendons, termed contractures, may occasionally develop, usually in the hands or feet; one example is the clenched fist contracture that may occur with prolonged flexion of a hand.

An accurate diagnosis of musculoskeletal pain is based on a careful history and a physical examination that takes into account posture, limb and trunk rigidity and gait. It can occasionally be challenging to distinguish between back pain due to PD and that caused by arthritis or scoliosis. Occasionally, further testing—including X-rays, bone scans, ultrasound and rheumatologic or orthopedic consultation—will be needed. The proper treatment of musculoskeletal pain in PD depends upon the cause of the pain. If the pain is the result of excessive immobility or rigidity, a physician may prescribe dopaminergic therapy, physical therapy and an exercise program. If the treatment is successful, patients should continue with an exercise program that strongly emphasizes range of motion, to prevent the development of further musculoskeletal problems.

Radicular and Neuritic Pain

Pain that occurs close to a nerve or nerve root is described as neuritic or radicular pain. The classic root-pain syndrome is sciatica, caused by compression or inflammation of the L5 lumbar root. Patients usually describe root pain as a sharp, lightning-like sensation that radiates towards the end of a limb. Of course, any nerve or root may be subject to injury or compression, and a careful neurological assessment is needed for the diagnosis. Electrodiagnostic studies and neuroimaging are occasionally required to confirm the location of the involved nerve or root, and to determine the cause of the problem. Radicular pain can usually be successfully treated with a mobility program and pain medication and rarely requires surgery.

Pain Associated with Dystonia

Dystonic spasms are among the most painful symptoms that a person with PD may experience. The pain arises from the severe, forceful, sustained twisting movements and postures that are called dystonia. This type of muscle spasm is quite different from the flowing, writhing movements described as dyskinesias, which are not painful. Dystonia in PD may affect the limbs, trunk, neck, face, tongue, jaw, swallowing muscles and vocal cords. A common form of dystonia in PD involves the feet and toes, which may curl painfully. Dystonia may also cause an arm to pull behind the back, or force the head forward towards the chest.

The most important step in evaluating painful dystonia is to establish its relationship to dopaminergic medication. Does the dystonia occur when the medication is at peak effect? Or does it occur as a “wearing-off” phenomenon, when the benefits of medication are waning? The answers to these questions will usually clarify the nature and timing of the dystonia, and determine its treatment. Most painful dystonia represents an “off” Parkinsonian phenomenon, and occurs early in the morning or during wearing-off spells. In uncertain cases, the neurologist should observe the patient in the office over a period of several hours in order to appreciate the relationship of the dystonia to the medication-dose cycle.

In terms of treatment, early-morning dystonia is typically relieved by physical activity, or by the first dose of dopaminergic medication, whether it be levodopa (Sinemet^®) or a dopamine agonist. When dystonia occurs as the medications wear off, the problem can be corrected by shortening the “off” period. In some patients, the dystonia is so severe that subcutaneous injections of apomorphine, with its onset of action in minutes, may be necessary. Individuals with intractable dystonia may benefit from deep brain stimulation, a neurosurgical procedure that involves implanting and activating electrodes in the brain.