Brain Stimulation to Treat Depression

As I have said in several columns to date, depression is one of the leading causes of disability worldwide. It is a serious, chronic condition that should not be ignored. Several effective treatments are available, but they don't work for everyone all of the time and the medications can cause troubling side effects in some people. There are still many people who remain chronically depressed in spite of best efforts with currently available treatments.

This is why researchers are always searching for new effective ways to treat depression that avoid as many side effects as possible.

Today there are a couple of new treatments in the research pipeline that have shown promising results to date and are taking us farther in our understanding of this disease. These methods involve stimulation of parts of the brain that are known to be involved in depression. All of these are still considered experimental (with the possible exception of transcranial magnetic stimulation). They are being used in cases of severe, intractable, treatment-resistant depression.

Essentially, research has shown that certain parts of the brain have abnormal activity -either they are abnormally inactive or overactive - in chronically depressed individuals. Scientists are trying to ascertain whether stimulating these areas of the brain in various ways can relieve symptoms in treatment resistant patients.Transcranial magnetic stimulation (TMS) is one method of depression treatment by brain stimulation. This is a non-invasive technique that activates the centres of emotion in the brain.

In TMS, the doctor holds a paddle-shaped device over the patient's forehead and the instrument emits a powerful magnetic field, which causes neurons in the prefrontal cortex of the brain to fire. Research shows that this region of the brain is under-active in depressed individuals.

TMS seems to produce similar results as Electro Convulsive Therapy (ECT) - during which an electric current is passed through the brain while the patient is sedated - however, in TMS no sedation is required and the results occur without the sometimes distressing side effect of memory loss that can occur in ECT.

So far, the evidence is strong that this technique has antidepressant effects when compared to sham treatment but there is need for more and larger studies. This treatment is available in Vancouver now but is quite expensive.Another new treatment that uses the same principles as ECT is magnetic seizure therapy (MST). This therapy uses magnetic fields rather than an electric current to induce a seizure. Using this technique, it is possible to more closely focus and better control what part of the brain is being stimulated. Although still under investigation for its effectiveness as an antidepressant, it appears that this added control helps to minimize memory loss side effects.

Another form of brain stimulation that is proving effective at treating depression is a surgically implanted device that stimulates the vagus nerve at the base of the neck. This was developed to treat epilepsy and patients began reporting improved mood as well.

The neurostimulator is approximately the same size as a cardiac pacemaker. It is implanted in the chest and there are wires connecting it to the vagus nerve. Although it seems to be effective, this technique is quite expensive - it is roughly $25,000 for the initial implant and has a recurring cost every five to 10 years when batteries need to be changed.

In a study of the vagus nerve stimulation technique, 40 per cent of treated patients experienced at least a 50 per cent or greater improvement in their condition and many were able to resume normal life activities. This is particularly impressive considering how treatment resistant these patients were.

Finally, there is deep brain stimulation, using electrodes in the brain, which may turn out to be the most exciting. This treatment is already approved for movement disorders, such as Parkinson's disease, and has produced dramatic results for some patients with those disorders.

Using this technique in depression, doctors target another area of the brain called the ventral anterior internal capsule and the ventral striatum. What researchers are finding is that deep brain stimulation is associated with significant and long term remission of depression in many cases. In some studies, patients report sudden calmness, heightened awareness and increased interest after a brain stimulation treatment. Studies are still in the preliminary stages, but this is showing some promise in treating depression and obsessive compulsive disorder.

Although still under investigation, these new brain stimulation techniques appear to be effective in treating depression. They are now also being studied for their effects in relieving other psychiatric disorders such as the mania associated with bipolar disorder, schizophrenia and obsessive compulsive disorder.

For those who still doubt the biological basis of depression, these treatments provide pretty compelling evidence.

As we understand more about the actual ways in which the brain is affected in many psychiatric conditions, it will be possible to continue developing more targeted and effective treatments.

 

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