KEY POINTS
■ Deep brain stimulation (DBS) is an FDA-approved surgical option available at most major metropolitan area hospitals for the treatment of patients with tremor, Parkinson disease, dystonia, and obsessive-compulsive disorder. Additional conditions are currently being studied for treatment with this method.
■ The procedure is performed by neurosurgeons and involves the implantation of a neurostimulation system composed of two wires (lead and extension); tiny electrodes at the tip of the lead wire deliver continuous electrical impulses to the patient.
■ The only current FDA-approved DBS device is manufactured by Medtronic (Minneapolis, MN). Four models are available that vary in both size and function.
■ Clinicians who provide long-term care for the patient, including PAs, must be aware of the potential complications associated with implanted neurostimulator systems when troubleshooting problems or assessing hardware issues.
■ As with any implanted device, the risk of skin erosion, hardware breakdown, wire migration, hardware infection, and sudden neurostimulator battery failure continue for the lifetime of the patient. Patients should be encouraged to routinely follow up with their DBS provider.
Deep brain stimulation (DBS) is an FDA-approved surgical treatment option for select patients with tremor, Parkinson disease, dystonia, and obsessive-compulsive disorder, all of which are commonly treated by primary care practitioners, emergency clinicians, and private practice neurologists.
1-3 Since the 1970s, DBS has been used to treat chronic central and peripheral pain.
4 In the past, patients traveled to academic centers for evaluation, implantation, and follow-up care. Today, most major metropolitan area hospitals offer DBS and more conditions are being studied for treatment with deep brain stimulation, including treatment-resistant depression, Tourette syndrome, treatment-refractory obesity, epilepsy, minimally conscious state, cluster headache, and addiction.
2,5-8 Now that deep brain stimulation has moved from the experimental realm to being an FDA-approved therapy, medical communities will encounter more and more patients with implanted DBS devices.
Patients who travel to have DBS surgery commonly return to their local communities for medical care.9 Given this trend, PAs should understand the unique issues that affect the general medical and surgical care of these patients. Focusing on DBS as treatment for movement disorders, this article describes how specialists evaluate patients for DBS, provides a general review of surgical procedures, and reviews the most common device-related problems or signs of disease progression after DBS implantation that may be encountered in the primary care office, emergency department, or general neurology office.
ABOUT THE PROCEDURE
Deep brain stimulation is an elective neurosurgical procedure performed by neurosurgeons trained in functional stereotactic techniques. Neurostimulation of selected brain regions is now known to override abnormal output of several brain nuclei that control movement. The mechanism of neurostimulation—whether stimulation drives neurons into a normal firing pattern or interrupts abnormal output to downstream nuclei—is under debate.10 The procedure involves the implantation of a neurostimulation system composed of two wires (lead and extension) and a neurostimulator that is similar in technology to a cardiac pacemaker. The neurostimulator delivers continuous electrical impulses to the tiny electrodes at the tip of the lead wire. Wires are implanted bilaterally if the patient experiences bilateral symptoms. With the exception of the intracranial portion of the lead wire, all other hardware components are implanted subcutaneously, as noted in the radiographs of the skull (Figure 1).
Patient selection Guidelines for patient selection are well-established.11,12 Many surgical teams have a neurologist, neuropsychologist, and neurosurgeon working together to select appropriate patients for DBS. For patients with tremor, dystonia, and Parkinson disease, the first step in the evaluation should be an assessment of symptoms by a neurologist, who establishes the diagnosis and reviews past and current treatments to ensure the patient has tried adequate medical therapies before undergoing brain surgery. A review of the patient and family's expectations for DBS is a crucial step in determining whether the surgery can meet these expectations.13 Patients with unrealistic expectations are generally not considered candidates for DBS. Many times, patients and families anticipate a return to a predisease state that is not possible with our current technology and is not likely with a progressive neurologic disorder. Treatments for patients with movement disorders may improve tremor, rigidity, bradykinesia, and dyskinesia; however, gait, balance, speech, and cognition are generally not responsive to stimulation. Realistic expectations are important since symptoms that are typically not responsive to dopamine often prompt patients to seek additional treatment. Generally, these symptoms are not responsive to DBS either.
Preliminary testing A patient with Parkinson disease also undergoes medication testing to evaluate his or her motor response to levodopa; the results predict the benefit that a patient should experience from optimal stimulation.14 The testing involves suspension of dopaminergic therapy overnight. An office visit is scheduled for the next morning for an examination of the patient in an off-medication state followed by administration of the patient's medication. Once the medication has taken effect and is improving symptoms, the patient is reexamined. A patient with Parkinson disease commonly wants surgery to improve gait shuffling, festination, and gait freezing; however, if his or her gait does not improve after the patient has taken a dose of levodopa, surgery is not likely to improve gait either. Medication testing is so important because the clinician is able to note—and the patient can experience—which symptoms improve with levodopa. These same levodopa-responsive symptoms should improve with appropriate surgical placement and adequate stimulation. During long-term care, knowing which symptoms should improve with stimulation helps immensely when troubleshooting problems or assessing hardware problems.
In addition, a recent international consensus statement finds leading deep brain stimulation experts to agree that neuropsychological testing should be performed to evaluate cognitive behavioral function, as patients with dementia or substantial behavioral symptoms are not generally considered for elective neurosurgery because of the importance of adhering to precautions and communicating reliably during long-term care.12,15,16 The neuropsychological testing includes an in-depth evaluation of the patient's cognitive function and mood as well as discussions about patient and family expectations for surgery and psychosocial issues that can impact the long-term management of the patient's condition. For instance, some patients with Parkinson disease have impulsivity or compulsivity control problems. If the patient chronically picks at his or her skin preoperatively, the risk of postoperative infection will likely be higher and additional counseling will be needed to monitor for picking at the incision sites. In addition, patients with compulsivity problems have been known to chronically manipulate the wires or manually flip the implanted neurostimulator over and over, which will lead to eventual wire damage and device failure.17