Globus Pallidus Interna Deep Brain Stimulation (GPI DBS) is a neurosurgical therapy that manages movement disorders by delivering controlled electrical impulses to the Globus Pallidus Interna. This is achieved through an implanted medical device, which includes a wire with electrodes in the brain and a power source in the chest, similar to a pacemaker. The goal of the therapy is to modulate abnormal brain signals that cause disruptive motor symptoms. This approach does not damage brain tissue and the system can be adjusted or turned off if needed.
Conditions Treated by GPI DBS
This therapy is a well-established treatment for several movement disorders, most notably Parkinson’s disease and dystonia, particularly when medications are no longer sufficient. For individuals with Parkinson’s, GPI DBS can improve motor symptoms like tremor and rigidity. It is also effective in reducing dyskinesia, the involuntary movements that can be a side effect of long-term levodopa medication. The treatment can lead to a 27–54% improvement in motor scores for Parkinson’s patients.
For dystonia, a condition of involuntary muscle contractions that cause twisting movements or abnormal postures, GPI DBS helps lessen these symptoms. It is a primary option for generalized or segmental dystonia that has not responded to other treatments. Younger patients and those with certain genetic forms of dystonia, such as DYT-1, often see the most significant benefit. The therapy has also been applied to other conditions, like Tourette’s syndrome, but its principal use remains for Parkinson’s and severe dystonia.
The Surgical Procedure
The implantation of a DBS system is performed in two parts. The first stage is brain surgery, where a neurosurgeon places thin wires, known as leads, into the Globus Pallidus Interna. To ensure exact placement, surgeons use advanced imaging techniques like MRI or CT scans to create a detailed map of the brain. A stereotactic head frame is attached to the patient’s skull to keep the head still, allowing the surgeon to guide the electrodes to their target.
During this part of the surgery, the patient may be awake to provide feedback. The surgical team might ask the patient to move their limbs or speak as they deliver test stimulation. This feedback helps confirm the electrodes are in the best location to control symptoms and avoid side effects. Once placement is confirmed, the permanent electrodes are secured.
The second stage, which can occur on the same day or a week later, involves implanting the neurostimulator device under the skin in the chest. An extension wire is then passed under the skin of the neck and shoulder to connect the brain electrodes to this power source.
Activation and Programming
Following the surgical implantation, the DBS system is not immediately activated. The initial programming session is scheduled several weeks after the surgery, allowing time for the brain to heal. During this appointment, a neurologist or trained clinician uses a wireless programmer to turn the device on and adjust the electrical settings. This process is tailored to the individual’s needs.
The initial programming involves a “monopolar review,” where each contact point on the electrode is tested. The clinician adjusts parameters like amplitude, pulse width, and frequency, starting with a low setting and increasing it gradually. The goal is to find the therapeutic window—the set of parameters that provides the greatest symptom relief with the fewest side effects. Achieving the best settings requires a series of appointments over several weeks or months to fine-tune the stimulation.
Outcomes and Long-Term Management
The results of GPI DBS can be significant, offering substantial improvement in motor control. For Parkinson’s patients, benefits include reduced tremor and rigidity, as well as a decrease in medication-induced dyskinesias. Patients with dystonia often experience a reduction in involuntary muscle contractions and improved posture.
However, DBS is a treatment, not a cure, as it does not stop the underlying disease progression. While motor symptoms may improve, other aspects of the condition, such as balance and gait issues, can worsen over time.
Living with a DBS system requires ongoing management. Stimulation can sometimes cause side effects, such as changes in speech, mood, or balance. These issues can often be resolved by making adjustments to the stimulation settings during follow-up programming appointments.
The battery in the neurostimulator also requires maintenance. Non-rechargeable batteries last, on average, three to five years and must be replaced through a minor outpatient surgical procedure. Rechargeable models require the patient to charge the device regularly.