Brain stimulation

Brain stimulation (neuromodulation) refers to a class of medical procedures used to stimulate or change the function of the nervous system in order to relieve the symptoms of depression, bipolar disorder, and related illnesses.

The major brain stimulation procedures include:

Electroconvulsive therapy (ECT)

Repetitive transcranial magnetic stimulation (rTMS)

Vagus nerve stimulation (VNS)



Electroconvulsive therapy (ECT)

ECT is a procedure, done under general anesthesia (patient is completely unconscious and unable to feel pain during the procedure), in which controlled electric currents are passed through the brain via electrodes attached to the scalp. The pulses excite brain cells, triggering brief seizures.ECT causes changes in brain chemistry that can quickly reverse symptoms of certain mental illnesses. This approach has been proven safe and effective for treating a variety of psychiatric illnesses that do not respond well to medication or therapy, especially severe depression.

In early ECT treatments, patients were administered high doses of electricity without anesthesia, which could lead to permanent memory loss and other serious side effects. ECT is much safer today thanks to significant improvements in the way the treatment is administered.

When is ECT recommended?

ECT is only recommended to treat severe cases of mental illness. ECT is generally used when severe depression is unresponsive to other forms of therapy or when someone is unable to tolerate the side effects associated with medications. ECT may also be the preferred treatment method when the situation is thought to be life threatening and a patient needs a more rapid response than medications or psychotherapy can provide.

The use of ECT is not limited to the treatment of depression. It may also be used to stabilize bipolar illness during extreme episodes of mania or depression. Additionally, ECT can be used to halt psychotic episodes associated with schizophrenia. Once these individuals are stabilized, medications are started or resumed.

There are multiple theories to explain why ECT is effective. The seizure activity itself may cause an alteration in neurotransmitters – the brain’s chemical messengers. ECT treatments also may adjust the brain’s regulation of stress hormones, affecting energy, sleep, appetite and mood. These and other mechanisms may interact to contribute to the effectiveness of ECT.

How are ECT treatments administered?

ECT is typically performed by a specially-trained healthcare team, including a psychiatrist, an anesthesiologist, and nursing staff. Before the procedure, the person is given a general anaesthetic and something to relax their muscles. Monitoring devices are placed on the patient’s head and upper body to monitor brain waves, heart rate, blood pressure and body movement during the procedure. When the patient is completely asleep, small electrodes are placed on one (unilateral) or both (bilateral) sides of the scalp and a small electric current is delivered. The person does not feel anything due to the anaesthetic, and does not convulse due to the muscle relaxant. The pulse causes one or more seizures that generally last 25 to 45 seconds. The entire treatment lasts approximately 10 to 20 minutes. By placing the electrodes in different locations to stimulate different areas of the brain, the timing of responses can be varied, which can increase effectiveness and decrease potential side effects.

Following treatment, the patient is fully monitored until they wake up. Most often the patient can return home with a caregiver the same day.

Patients are normally scheduled for three treatments per week, for a total of six to twelve treatments, although sometimes upto 18 treatments are used. The exact number is determined by the severity of symptoms and how rapidly the patient responds. Generally, symptoms start to improve after three sessions.

Side effects of ECT

  • Immediate side effects include:

  • Headaches

  • Muscle aches

  • Nausea

  • Mental confusion

  • Temporary loss of memories or difficulty in creating new memories

Generally, these side effects go away within a few hours, although a few people experience long-term or even permanent loss of some memories. Bilateral treatment may affect a patient’s memory more than unilateral treatment. In addition, the more treatments someone has, the greater the potential for memory loss.

Is ECT safe?

Any medical procedure carries some risk. The risk involved in ECT is regarded as similar to having an uncomplicated outpatient surgical procedure under anesthesia. ECT treatments themselves are very safe and severe complications are rare.

What comes after ECT?

Depression is a relapsing illness – especially when left untreated. It’s common for a patient to experience repeated episodes of depression, even after responding well to ECT. Particularly when a patient has responded poorly to medications prior to ECT, the doctor may recommend a “tapered” series of ECT treatments (like one treatment every 2 weeks) for “maintenance” over the course of several weeks or months to regulate depression.

It is also important to note that ECT is only one component of an individual’s treatment plan. After ECT, medications and/or psychotherapy may be prescribed to manage symptoms and help patients cope better with the stressors of life. In addition, an individual’s own self care habits are important to the overall success of the treatment plan.

Repetitive Transcranial Magnetic Stimulation (rTMS, or TMS)

TMS is a non-invasive procedure that has been extensively studied for the treatment of depression and other brain disorders. TMS involves placing a coil on the scalp that generates a brief magnetic field, which is repeated about 10 times/second, or, in some cases, every second (hence, ‘repetitive’ TMS, or ‘rTMS’). The magnetic field stimulates neurons in the brain, which can help to alleviate symptoms of depression. A session of treatment lasts around 30 minutes, depending upon how the therapy is prescribed. TMS sessions occur daily (five times/week), over a course of five to six weeks. Studies show that, on average, about half of patients experience a significant benefit from treatment, which usually occurs after 2-3 weeks of therapy.

When is TMS recommended?

TMS was approved by the U.S. Food and Drug Administration in 2008 for the treatment of major depressive disorder in adults who have failed to improve with antidepressant medications.

How are TMS treatments administered?

Because the coil is positioned against the side of the head, the procedure does not require intravenous needles, incisions or anesthesia. TMS can be administered in an office setting.

What are the side effects of TMS?

Stimulation can produce significant pain in the initial phase of treatment, but most patients find that the initial pain reduces significantly during the first week of treatment. Also, adjustments to stimulation can reduce the initial pain, which only occurs during stimulation. After a session, some patients report headaches, and occasionally experience sleep disturbance.

Is TMS safe?

TMS is a very safe treatment, and serious side effects are rare. However, TMS should only be prescribed and administered by a licensed physician. Patients with seizure disorders or other medical conditions such as brain tumors may not be candidates for TMS.

Vagus Nerve Stimulation (VNS)

VNS sends regular, mild pulses of electrical energy to the brain at regular intervals via the vagus nerve, through a device that is similar to a pacemaker. VNS uses electrical impulses to help reset chemical imbalances and stimulate centers in the brain that regulate mood, sleep, appetite and motivation. In 2005, VNS was approved for the treatment of both chronic or recurring depression and bipolar disorder.

How is VNS administered?

A battery-operated, computer-controlled device the size of a pocket watch (called a pulse generator), is surgically implanted in the upper chest, just below the collarbone. Wires attach it to the left vagus nerve, which runs from the brain through the neck and into several major organs. Electrical pulses travel from the generator to the vagus nerve. When stimulated, the nerve sends signals to the brain.

Is VNS effective?

VNS has been shown to be significantly helpful in about 30% of patients treated for chronic depression or Type II bipolar affective disorder, The therapeutic effects of VNS appear to accumulate over time, with some patients needing up to a year of treatment to see a full effect. Studies have also shown that the improvement can be long lasting. Patients who saw improvement within 12 months showed nearly a 70% chance of retaining a positive response after two years.

When is VNS recommended?

The U.S. Food and Drug Administration has approved VNS for patients 18 years and older who have long term, chronic depression that has lasted two or more years, recurrent or severe depression, or depression that has not improved after the use of other treatments.

It is recommend that patients have had a course of evidence-based psychotherapy for depression, such as Cognitive Behavioral Therapy (CBT) or Interpersonal Therapy (IPT). Patients are also strongly encouraged to try Electroconvulsive Therapy (ECT) before considering VNS.

What is involved in the VNS procedure?

An outpatient surgical procedure lasting one to two hours is required to implant the VNS system, and most patients go home the same day. The surgery involves making two small incisions: one in the upper chest area, where the pulse generator is placed and another on the left side of the neck, where the wires are attached to the vagus nerve. A week or two after the surgery, the doctor will turn on the stimulator during an office visit, and will gradually adjust the strength of stimulation over several weeks. However, new devices are being tested that can be simply applied directly to the neck without any surgery, and these likely will replace surgical VNS.

What are the side effects of VNS?

VNS does not cause the side effects encountered with many medications, such as memory loss, sleep difficulty, weight gain or sexual dysfunction. During the 30-second stimulations, patients may experience temporary voice changes and hoarseness, difficulty swallowing, tightness in the throat, increased muscle tension, difficulty breathing, headache, nausea, neck pain, numbness and tingling at the incision site, coughing, dizziness, and/or chest pain.

A disadvantage of VNS is that for patients who do not benefit from stimulation (the majority), the device needs to be removed. However, the wires attaching the battery pack to the vagus nerve is usually not removed.

Is VNS safe?

The treatment requires surgery, making it more invasive than other treatments for depression. Any medical procedure involving anesthesia carries some risk.

What comes after VNS?

VNS is not a quick fix, and it is not a cure for depression. VNS is considered a long-term therapy, and while many patients may require less medication as a result of VNS, they may still need some drug therapy to manage their symptoms. Some patients may have no improvement, or even worsen with VNS therapy.

After several years, the batteries in the VNS device must be replaced, which involves another short outpatient surgical procedure.

Experimental brain stimulation therapies

Brain stimulation is a very active area of research, and many devices to deliver energy to the nervous system are being studied. In some cases, the techniques are approved for other disorders, and some providers can make them available for depressed patients ‘off label,’ meaning that they use the device to treat depression when it was not approved for depression. Other devices are simple enough that they can be purchased by individuals and self-administered. However, patients should be cautioned that using devices that have not passed the rigorous testing required by the FDA to demonstrate that a device actually works puts a patient at some risk. At a minimum, they may be wasting their time and money. Patients should always consult with their physician before undertaking the use of any non-approved device.

Deep brain stimulation (DBS), which is approved for the treatment of certain neurological conditions like Parkinson’s disease, involves the implantation of electrodes directly into the brain, usually to deep brain regions involved in the regulation of mood and known to be involved in depression. The procedure is considered invasive, because surgeons have to open holes in the skull to insert the electrodes, which are attached to a battery pack stimulator, implanted under the skin of the chest wall, much like a heart pacemaker. Preliminary studies have demonstrated some promising results in the treatment of chronic, treatment-resistant depression, but larger, more controlled studies have not confirmed the early, promising effects. However, work continues to refine the technique, which may yet yield a therapy that would be approved for treatment.

A non-invasive from of brain stimulation, not currently approved, is transcranial direct current stimulation (tDCS), and variations that use alternating current rather than direct current. These devices typically use energy from a small battery to apply current directly to the scalp, and treatment is applied for 10 - 30 minute periods. Preliminary research has shown some benefits for people with depression, although the technique has not yet been well-tested on people with more chronic forms of depression. Although these devices can be purchased for self-administration, they have not been approved by the FDA for the treatment of depression.

References

Milev, R. V., Giacobbe, P., Kennedy, S. H., Blumberger, D. M., Daskalakis, Z. J., Downar, J., ... & MacQueen, G. M. (2016). Canadian Network for Mood and Anxiety Treatments (CANMAT) 2016 clinical guidelines for the management of adults with major depressive disorder: section 4. Neurostimulation treatments. The Canadian Journal of Psychiatry, 61(9), 561-575.