What is the purpose of deep brain stimulation?

Deep brain stimulation (DBS) is a surgical technique, introduced since the late 1980s, that can mitigate the symptoms of Parkinson's disease and the complications induced by drug therapy. The effectiveness of deep brain stimulation has recently been confirmed by randomized controlled trials performed according to the principles of evidence-based medicine. "The patients who undergo deep brain stimulation are subjects who have an inconsistent response to therapy, have abnormal involuntary movements, the dyskinesias, side effects of drug therapy, and long-term complications of levodopa.

What is Deep Brain Stimulation?

DBS (Deep Brain Stimulation-Deep Brain Stimulation) is an intervention technique indicated for patients suffering from serious neurological diseases. Deep brain stimulation (DBS) is able to provide important clinical benefits in patients with Parkinson's disease, essential tremor, dystonia, chronic pain (some forms), obsessive-compulsive disorders, and major depression. DBS, being an invasive treatment, is never indicated as a first cure; the indication for intervention is given when drug therapy, usually after many years, becomes ineffective or burdened with many side effects.

The deep brain stimulation (deep brain stimulation, DBS) involves the insertion of an electrode in a precise point of the brain connected to a pulse generator (a pacemaker) in the subcutaneous region of the thorax. The small electrical impulses that reach the brain help to achieve a temporary but significant reduction in the most obvious symptoms of Parkinson's disease, such as tremors in movement.

A limited number of patients, at an advanced stage of the disease and not very sensitive to drugs, end up receiving treatment. But in the face of satisfactory results, the reason for the operation of DBS has long remained unclear. The new study appears to indicate that deep brain stimulation increases and fortifies the "cells" of the brain cells, the mitochondria. This benefit would reactivate damaged neurons resulting in motor improvement.

Therapy is indicated in severe forms of:

- Parkinson's disease

- Dystonia

- Tremor

- Tourette syndrome

- Obsessive-compulsive disorder 

- Epilepsy and major depression (in-depth scientific studies are still ongoing)

The intervention is indicated only in 10% of patients with Parkinson's disease when motor fluctuations and dyskinesias are no longer kept under control by drugs; patients must not be older than 70 and must not present other major health problems. In any case, patients who undergo surgery must respond positively to the pharmacological treatment of Parkinson's disease (levodopa). Before carrying out the treatment, the patient will undergo joint assessments by the neurosurgeon and neurologist such as mental state, daily activities, motor functions, possible complications that may arise with therapy, stage and progression of the disease. Tremor, stiffness, akinesia, and disorders of the DBS consists of inserting an electrode in a specific area of ​​the brain, connected to a neurostimulator (a sort of pacemaker) located in the upper chest area or in the abdomen. The pacemaker will send electrical impulses to the brain, aimed at reducing the symptoms of the specific pathology.

Depending on exactly the type of pathology, the neurosurgeon will decide in which area of ​​the brain to place the electrode. The lead is implanted in the subthalamic nucleus in the case of Parkinson's disease, in the intermediate ventral nucleus if it is used to relieve essential tremor and in the nucleus of the pale globe for dystonia, by stimulating the various nuclei the signals that cause motor symptoms are blocked disabling diseases.

The DBS system is composed of:

- A lead, a thin cable that is composed of electrodes at the end and is implanted in the affected area of ​​the brain via a small hole in the skull.

- An extension: a wire that runs from the skull to the upper chest area and connects the lead to the neurostimulator.

- A neurostimulator (pacemaker): a device with electronic components, due to which it can work, and the battery that gives energy. This appliance is placed under the skin of the chest or abdomen and produces electrical impulses for stimulation.

Treatment can be divided into two phases:

1. Initially, the patient undergoes local anesthesia in the area of ​​the scalp, where the leads are then positioned to accurately determine the specific area for surgery; the neurosurgeon uses the images and the stereotaxic helmet that is fixed to the skull with screws.

2. Subsequently, the operation is carried out with the patient under general anesthesia, the neurostimulator is implanted in the abdomen or thorax area, and the leads are connected to a thin extension cable positioned under the skin. 

Once the surgery is over, the patient will have to stay 3-4 days in the hospital for observation; after a few weeks, the DBS will be programmed according to the patient's clinical needs.

Once activated, the neurostimulator always remains on. When the battery runs out (usually after 4-5 years, but the time depends on the intensity of the stimulation), a small battery replacement surgery is performed. In some patients, it is possible to use a rechargeable stimulator whose duration is much longer.

The risks associated with DBS are low and, in particular, they can be:

- intracranial hemorrhage (1% of cases)

- device infection

- convulsions

The side effects that the patient may experience the following stimulation are:

- apathy

- hallucinations

- compulsive gambling

- hypersexuality

- cognitive dysfunction and depression

- dysarthria 

- paresthesia

The treatment can be reversible; in fact, the DBS can be turned off at any time.

Most patients do not perceive the stimulation, in rare cases, however, a sense of tingling; paresthesias can be experienced when the device is turned on; Furthermore, it is right to make the patient understand that this intervention technique does not involve healing from neurological disease, but allows reducing the symptoms.

Parkinson's disease

Parkinson's disease, which according to some estimates would affect at millions of people, involves the progressive loss of cells in an area of ​​the brain called the substantia nigra (SN) or black substance, which produces the dopamine neurotransmitter, essential for distributing the "commands" for controlling body movements. Those affected by the disease experience tremors, slowness, and uncertainty in starting to move, dysphagia (difficulty swallowing) symptoms that make managing everyday activities increasingly complex.

Author: Vicki Lezama