Epilepsy: Neuromodulation

OVERVIEW

Over the last decade, multiple surgical options have become available for patients with epilepsy that does not respond to medication. These include vagal nerve stimulation (VNS), responsive neurostimulation (RNS) and deep brain stimulation (DBS). These devices may be used for different types of epilepsy when patients have tried and failed two or more anti-epileptic drugs (AEDs). Which device is best for the patient is decided by the treating neurologist. The patient is likely to continue on AEDs even after the device is implanted, but the goal is to reduce the number of and the severity of seizures. Neurostimulation devices may be used to alter abnormal brain activity.

RNS involves placing two electrodes on the surface of the brain or into the brain, in or around the area which is most likely the onset region for the seizure. The device records brain waves (EEG). EEGs that show seizure onset are recognized and then an impulse is delivered to stop a seizure. The patient can upload the data collected by the neurostimulator to a secure web-based application so the neurologist can access it. In DBS, electrodes are placed in the brain, but instead of being placed in an area with seizure, they are placed in an area that serves as a relay station for brain signals.

Determining a Course of Treatment

RNS is used as a treatment for adults with partial-onset seizures with one or two seizure onset zones and whose seizures have not been controlled with two or more antiepileptic drugs. DBS is used as a treatment for adults with focal seizures who have not been responsive to two or more antiepileptic drugs and could not be treated with other types of epilepsy surgery.

RNS and DBS are used when a patient’s epilepsy does not respond to anti-seizure medications and they are not suitable candidates for other epilepsy surgeries.

Individuals with any of the following criteria may be unsuitable candidates for neuromodulation:

• Symptoms are not substantially reducing a patient’s quality of life
• Symptoms can be controlled with medications with minimal side effects
• Diagnosis other than focal epilepsy
• Suitable candidate for resective or other epilepsy surgeries

Symptoms

Patients with epilepsy commonly experience the following symptoms:

• Temporary confusion
• A staring spell
• Loss of consciousness
• Uncontrollable jerking movements of arms or legs
• Emotional responses such as fear, anxiety or déjà vu

Testing & Diagnosis

Before surgery, the patient is evaluated by a neurologist to determine if the type of epilepsy is best treated by neuromodulation. The implanting neurosurgeon will take a full history and physical examination to ensure that the patient is a good surgical candidate.

Surgery

This procedure, performed by a neurosurgeon, usually takes about two to three hours. The patient usually stays overnight. There is a small risk of infection. Other surgical risks include inflammation or pain at the incision site. The device may malfunction, similar to any other electrical device.

The procedure may be done at one or two settings. During the first phase of the surgery, electrodes are inserted through a hole in the skull and placed inside the brain at the appropriate spot using pre-operative information. The battery may be placed at the same time in the skull for RNS or in the chest for DBS. Often the DBS surgery battery placement is performed at a second stage.

The battery looks like a heart pacemaker. Newer devices may be smaller. Some batteries must be charged daily while others do not require charging. All batteries need to be replaced at some point with a less invasive procedure that requires only opening the incision, but no additional work in the brain.

Follow-up

The stimulator is most commonly activated two to four weeks after implantation. The treating neurologist programs the stimulator in his or her office with a small hand-held computer. The amount of stimulation varies by case, but is usually initiated at a low level and slowly increased to a suitable level for the individual.

Possible Side Effects

It may take several months before patients notice improvement in seizures. Side effects are most commonly related to stimulation and usually improve over time.

• Feelings of muscle tightness
• Changes in voice/speech
• Loss of balance
• Impaired vision
• Numbness or tingling sensations
• Lightheadedness
• Unwanted mood changes

These symptoms are only temporary while patients adjust to their new devices. Altering the stimulation may relieve symptoms. Patients should let the doctor know if these symptoms occur. In addition, patients should call their physician before undergoing any medical tests that might affect, or be affected by, neuromodulation or before you have any other surgery.

Latest Research

Currently Recruiting

• Deep Brain Stimulation Post Failed Vagal Nerve Stimulation (DBS post VNS)
• Hippocampal and Thalamic DBS for Bilateral Temporal Lobe Epilepsy
• Medtronic Deep Brain Stimulation (DBS) Therapy for Epilepsy Post-Approval Study (EPAS) (EPAS)

Recently Published

• Herrman H, Egge A, Konglund AE, Ramm-Pettersen J, Dietrichs E, Taubøll E. Anterior thalamic deep brain stimulation in refractory epilepsy: A randomized, double-blinded study. Acta Neurol Scand. 2019 Mar;139(3):294-304: This study investigated the benefit of DBS in patients with refractory epilepsy. The study concluded that benefit of VNS may be compounded by continuation of anti-epileptic drugs. The study concluded that DBS is a safe and effective treatment option for patients with refractory epilepsy.
• Geller EB, Skarpaas TL, Gross RE, Goodman RR, Barkley GL, Bazil CW, Berg MJ, Bergey GK, Cash SS, Cole AJ, Duckrow RB, Edwards JC, Eisenschenk S, Fessler J, Fountain NB, Goldman AM, Gwinn RP, Heck C, Herekar A, Hirsch LJ, Jobst BC, King-Stephens D, Labar DR, Leiphart JW, Marsh WR, Meador KJ, Mizrahi EM, Murro AM, Nair DR, Noe KH, Park YD, Rutecki PA, Salanova V, Sheth RD, Shields DC, Skidmore C, Smith MC, Spencer DC, Srinivasan S, Tatum W, Van Ness PC, Vossler DG, Wharen RE Jr, Worrell GA, Yoshor D, Zimmerman RS, Cicora K, Sun FT, Morrell MJ. Brain-responsive neurostimulation in patients with medically intractable mesial temporal lobe epilepsy. Epilepsia. 2017 Jun;58(6):994-1004: This study investigated the reduction in seizures and the safety of RNS in patients with partial-onset seizures. The study concluded that benefit of RNS is a safe and effective treatment option for seizure reduction in patients with partial-onset seizures.

Resources for More Information

• Sara’s Story of how DBS helped her epilepsy
• Drew’s Story of how RNS helped his epilepsy