Project Summary-Deep Brain Simulation

Deep Brain Stimulation

-Aript Agarwal & J Ajay Reddy

Deep brain stimulation (DBS) is a neurosurgical procedure involving the implantation of a medical device called a brain pacemaker, which sends electrical impulses, through implanted electrodes, to specific parts of the brain.DBS in select brain regions has provided therapeutic benefits for otherwise-treatment-resistant movement and affective disorders .

How it came into existence?

In the early 1950s, doctors found lesioning surgery.

When areas of the brain involved in certain movement disorders were lesioned (destroyed), the symptoms often improved but this is not always effective. Also it sometimes resulted in damaging side effects. Their effects cannot be undone; a lesioned brain structure is permanently destroyed. As a result, unwanted side effects are usually irreversible.

In the 1970s a new drug therapy using levodopa replaced lesioning surgeries. it does not involve any risky brain surgeries and dosages could be adjusted to suit individual needs but on prolonged usage brain eventually compensates for the effects of the drugs.

Patients were developing new movement control problems that were considered worse than the original symptoms.

Then, in the late 1980s, a new discovery was made. Experts found that the same effects caused by lesioning brain tissue could be achieved by stimulating the tissue with harmless pulses of electricity. This is DBS.

The effects of electrical stimulation are completely reversible. In fact, when the stimulation is turned off, the brain resumes its normal behavior.

Similar to drug treatments, doctors could tailor the electrical stimulation to fit the exact needs of each patient. Unlike drug treatments, the electrical stimulation could be localized so that only intended parts of the brain were affected.

An implantable deep brain stimulation (DBS) device is made up of three main parts:

  1. Electrode

The electrode is a small tip-shaped device (like plug of headphones) ,implanted deep into the region of the brain involved with the disease symptoms. Its surface has four metal pads used to transmit pulses of electricity. These pulses of electricity are small and only stimulate the brain tissue within close range of the electrode. This ensures to specifically target only the brain region closest to where the electrode is implanted.

Pulse Generator

The pulse generator (stimulator) is a small, box-shaped device that generates the electrical signals that are sent to the electrode. It is usually implanted under the skin in a space near the patient’s chest. It has a battery (lifespan :2-7 yrs).

The electrical patterns are generated in quick on-off pulses delivered at very high frequencies — usually over 100 times per second. Only at these high frequencies does the stimulation help reduce the unwanted symptoms.

Extension

  • Extension is simply an insulated cable that carries the electrical signals from the pulse generator to the electrode implanted in the brain.
  • Having any part of the DBS device go through the skin would create a risk of infection, so the surgeon typically tunnels a small path under the skin from the pulse generator to the electrode.

Working principle

Few possible explanations:

The quickly repeating electrical signals emitted by the DBS electrode may act to block irregular brain activity. In this scenario, the effects of the electrical stimulation can be thought of as a gate blocking certain pathways of corrupted information.

Another possibility is that the regular pattern of electrical pulses from the implanted DBS electrode would act to override irregular flows of information. In other words, the electrical stimulation of the DBS device acts to drown out the abnormal patterns of brain activity.

Following diseases could be cured by DBS-

  1. Parkinson’s disease
  2. Dystonia
  3. Chronic pain
  4. Major depression
  5. Tourette syndrome
  6. Adverse effects
  7. While DBS is helpful for some patients, there is also the potential for neuropsychiatric side-effects, including apathy, hallucinations, compulsive gambling, hypersexuality, cognitive dysfunction, and depression.
  8. It is possible that the electrodes are displaced or dislodged causing more profound complications such as personality changes. But electrode misplacement is relatively easy to identify using CT.
  9. There may also be complications of surgery, such as bleeding within the brain. After surgery, swelling of the brain tissue, mild disorientation, and sleepiness are normal.
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