Deep brain stimulation: What can patients expect from it?
ABSTRACTDeep brain stimulation has largely replaced ablative procedures for the treatment of advanced Parkinson disease, essential tremor, and dystonia. It is also approved for obsessive-compulsive disorder. Although not curative, it improves symptoms and quality of life.
KEY POINTS
- Compared with ablative procedures, deep brain stimulation has the advantage of being reversible and adjustable. It is considered safer than ablative surgery, in particular for bilateral procedures, which are often needed for patients with advanced Parkinson disease and other movement disorders.
- For Parkinson disease, deep brain stimulation improves the cardinal motor symptoms, extends medication “on” time, and reduces motor fluctuations during the day.
- In general, patients with Parkinson disease are likely to benefit from this therapy if they show a clear response to levodopa. Patients are therefore asked to stop their Parkinson medications overnight to permit a formal evaluation of their motor response before and after a dose of levodopa.
- Candidates require a thorough evaluation to assess whether they are likely to benefit from deep brain stimulation and if they can comply with the maintenance often required for a successful outcome.
Deep brain stimulation is an important therapy for Parkinson disease and other movement disorders. It involves implantation of a pulse generator that can be adjusted by telemetry and can be activated and deactivated by clinicians and patients. It is therefore also a good investigational tool, allowing for double-blind, sham-controlled clinical trials by testing the effects of the stimulation with optimal settings compared with no stimulation.
This article will discuss the approved indications for deep brain stimulation (particularly for managing movement disorders), the benefits that can be expected, the risks, the complications, the maintenance required, how candidates for this treatment are evaluated, and the surgical procedure for implantation of the devices.
DEVICE SIMILAR TO HEART PACEMAKERS
The deep brain stimulation system must be programmed by a physician or midlevel practitioner by observing a symptom and then changing the applied settings to the pulse generator until the symptom improves. This can be a very time-consuming process.
In contrast to heart pacemakers, which run at low frequencies, the brain devices for movement disorders are almost always set to a high frequency, greater than 100 Hz. For this reason, they consume more energy and need larger batteries than those in modern heart pacemakers.
The batteries in these generators typically last 3 to 5 years and are replaced in an outpatient procedure. Newer, smaller, rechargeable devices are expected to last longer but require more maintenance and care by patients, who have to recharge them at home periodically.
INDICATIONS FOR DEEP BRAIN STIMULATION
Deep brain stimulation is approved by the US Food and Drug Administration (FDA) for specific indications:
- Parkinson disease
- Essential tremor
- Primary dystonia (under a humanitarian device exemption)
- Intractable obsessive-compulsive disorder (also under a humanitarian device exemption). We will not discuss this indication further in this paper.
For each of these conditions, deep brain stimulation is considered when nonsurgical management has failed, as is the case for most functional neurosurgical treatments.
Investigations under way in other disorders
Several studies of deep brain stimulation are currently in progress under FDA-approved investigational device exemptions. Some, with funding from industry, are exploring its use in neuropsychiatric conditions other than parkinsonism. Two large clinical trials are evaluating its use for treatment-refractory depression, a common problem and a leading cause of disability in the industrialized world. Multiple investigators are also exploring novel uses of this technology in disorders ranging from obsessive-compulsive disorder to epilepsy.
Investigation is also under way at Cleveland Clinic in a federally funded, prospective, randomized clinical trial of deep brain stimulation for patients with thalamic pain syndrome. The primary hypothesis is that stimulation of the ventral striatal and ventral capsular area will modulate the affective component of this otherwise intractable pain syndrome, reducing pain-related disability and improving quality of life.
DEEP BRAIN STIMULATION VS ABLATION
Before deep brain stimulation became available, the only surgical options for patients with advanced Parkinson disease, tremor, or dystonia were ablative procedures such as pallidotomy (ablation of part of the globus pallidus) and thalamotomy (ablation of part of the thalamus). These procedures had been well known for several decades but fell out of favor when levodopa became available in the 1960s and revolutionized the medical treatment of Parkinson disease.
Surgery for movement disorders, in particular Parkinson disease, had a rebirth in the late 1980s when the limitations and complications associated with the pharmacologic management of Parkinson disease became increasingly evident. Ablative procedures are still used to treat advanced Parkinson disease, but much less commonly in industrialized countries.
Although pallidotomy and thalamotomy can have excellent results, they are not as safe as deep brain stimulation, which has the advantage of being reversible, modulating the function of an area rather than destroying it. Any unwanted effect can be immediately altered or reversed, unlike ablative procedures, in which any change is permanent. In addition, deep brain stimulation is adjustable, and the settings can be optimized as the disease progresses over the years.
Ablative procedures can be risky when performed bilaterally, while deep brain stimulation is routinely done on both hemispheres for patients with bilateral symptoms.
Although deep brain stimulation is today’s surgical treatment of choice, it is not perfect. It has the disadvantage of requiring lifelong maintenance of the hardware, for which the patient remains dependent on a medical center. Patients are usually seen more often at the specialized center in the first few months after surgery for optimization of programming and titration of drugs. (During this time, most patients see a gradual, substantial reduction in medication intake.) They are then followed by their physician and visit the center less often for monitoring of disease status and for further adjustments to the stimulator.
Most patients, to date, receive nonrechargeable pulse generators. As mentioned above, the batteries in these devices typically last 3 to 5 years. Preferably, batteries are replaced before they are completely depleted, to avoid interruption of therapy. Periodic visits to the center allow clinicians to estimate battery expiration ahead of time and plan replacements accordingly.
Rechargeable pulse generators have been recently introduced and are expected to last up to 9 years. They are an option for patients who can comply with the requirements for periodic home recharging of the hardware.
Patients are given a remote control so that they can turn the device on or off and check its status. Most patients keep it turned on all the time, although some turn it off at night to save battery life.
