Deep Brain Stimulation

What is Deep Brain Stimulation (DBS)?

Deep brain stimulation (DBS) is a stimulation technique which requires surgical implantation of a neurostimulator. It is often described as a pacemaker for the brain. DBS is commonly used to initiate controlled movements. A pulse generator is used to generate electrical impulses. These impulses are then transmitted to the brain which changes or interrupts the abnormal activity of the brain, leading to controlled motor activity. After the approval of the Food and Drug Administration (FDA), DBS was used in 1997 for tremor and 2003 for Parkinson disease (PD). At present more than 40,000 people with PD and essential tremor have been treated worldwide. DBS can be used for the treatment of various other neurological disorders like dystonia, tremors, obsessive-compulsive disorder (OCD), epilepsy, essential tremor, Tourette’s syndrome etc. Other than motor-related disorders, it can also serve as the potential treatment for depression, dementia, stroke recovery, chronic pain, addiction etc.

Components of Deep Brain Stimulation

Electrodes: Electrodes are thin insulated wires and might be of different types such as ring contact, segmented ring contact, 4 contacts, 8 contacts etc.
Pulse generator: A pulse generator is a neurostimulator. It functions in the same way for the brain as a heart pacemaker does for the heart sending constant electrical pulses. It comprises a battery and an electronic circuit embedded in it.
Extension: An extension does the job of establishing the connection between the electrode and the pulse generator.
Remote Controller: The pacemaker can be turned off or on using a hand handled device called controller, depending upon the health condition of the patient as per the doctor’s suggestion. The battery level can also be checked using it.

Technical factors of Deep Brain Stimulation system

To maximize the desired therapeutic effect, the well-shaped stimulation field is required. Some of the technical features of DBS systems are discussed below.

The electrical source for DBS might be current or voltage source. The classical one is voltage source but at present many systems have come up with the current source.
Depending upon the number of connectors on the header of the pulse generator, unilateral or bilateral stimulation can be performed.
The more precise and targeted is the electrical stimulation field, the more localized the neuronal response. The field depends on three factors namely distribution of current, rate of stimulation, and pulse width.
The electrode design, the polarity, the proportion of current coming from each contact, and the amplitude controls the current distribution.
Batteries used in the pulse generator can be rechargeable or non-rechargeable.
Desirable properties of the stimulation can be set by programmers using radio frequency coupling.
The interconnectivity among the components of DBS is independent of the manufacturer and can be achieved by using adaptors.

Advantages of DBS

Over the past 20 years to till date, DBS has been used to treat around 1,60,000 people with different neurological symptoms. It gives a new ray of hope to people with neurological disorders having been failed by medicines and other therapeutic measures. However, it is to be noted, it cannot cure the disorder completely. It helps in reducing the symptoms and leading a better life. It is a replacement of the ablative procedures. The advantages of it are enlisted below:

Safer, minimally invasive and effective compared to other surgical procedures which include tissue removal.
Damage involved is less so chances of long-term complications are low. The traditional procedures mostly involve damaging some organs.
Customization and flexibility of adjustment of simulators according to the need of the patients
Bilateral implantation of DBS is possible if required.
Alterations can be made in the future if required.
Improves the quality of life by helping patients regain significant and controlled mobility.
Continuous monitoring of symptoms is possible with DBS
Less relying on medicines which help in reducing the side effects of medications.

Steps of DBS

A small hole is drilled on the skull and the electrode is inserted in the area of interest in the brain after computed tomography (CT) or magnetic resonance imaging (MRI) scan. Electrode implantation can be done either in the awake state or by using general anaesthesia depending upon the disorder. The optimal area of electrode placement is a very crucial step and is based on feedback from the patients when alert. Whereas in general anaesthesia, they have to depend completely on CT or MRI scans to target the area of interest.
After a week or so, the battery-powered pulse generator is implanted usually under the skin in the upper chest
To connect the electrode already implanted in the brain with the pacemaker an extension is used.
After the surgery, the pulse generator can be remotely programmed by the doctor. The stimulation rate needs to be optimized.

Risks with Deep Brain Stimulation

Every surgical procedure has risk involved in it, no matter how meticulously it has been carried out. It is suggested by doctors only when there are no hopes of recovery from medicines or physical therapy. The patients need to undergo a lot of evaluation steps before they are recommended to go for DBS. The tests include blood and urine tests (to identify the toxicity level in the body), MRI or CT scanning (helps in targeting the correct area for relieving the patients’ disorder) and overall body check-up (if there are any other complications or disease). After getting medical clearance, the patient is under the surveillance of a team of experts from different fields which includes a neurologist, neurosurgeon, neuropsychologist and psychiatrist.

Future Scope

Smartphone-based controllers for stimulators.
Techniques for optimization of the electrode implant position.
Widening the spectra of application of DBS, for instance, addressing freezing and balancing issues.
To make DBS more advanced by miniaturizing scopes, incorporating more features in hardware.
Further research is in need to understand the proper efficacy of DBS and its side-effects.
There is a need for non-invasive DBS that will relieve the patients from a painful surgical procedure. This may enhance the acceptance of DBS.
There is a need for user friendly design of the complete DBS system.