Among the treatments presented below, transcranial magnetic stimulation and transcranial direct current stimulation are non-invasive procedures, meaning that they require no cut or break in the skin and no penetration into body cavities beyond their natural borders.
Repetitive Transcranial Magnetic Stimulation (rTMS)
Repetitive Transcranial Magnetic Stimulation is a promising option for those whose OCD has not responded well to CBT and/or drug treatment. It is a method that has been used with some success in the treatment of several other types of mood disorders (120, 121). The procedure uses an electromagnetic coil that is placed on the scalp over those specific areas of the brain suspected to play a role in several neuropsychiatric disorders, including anxiety and obsessive-compulsive disorder. The coil emits repetitive magnetic pulses that pass into the brain directly underlying the coil. The magnetic pulses are thought to work by creating tiny electric currents that stimulate or inhibit nerve cell activity in the area under the magnetic coil (122). With the exceptions of headaches, and pain or discomfort at the site where the coil is placed, the procedure is generally well tolerated by the majority of patients. Serious side effects are rare and include episodes of fainting and, even less common, seizures. Other risks are predominantly transient, including hypomania, hearing loss, cognitive changes and short-term memory impairment (123). There are numerous drugs that should be used with caution in conjunction with rTMS, primarily because of increased seizure risks (123). Therefore, before beginning rTMS, drug regimens should be carefully reviewed by a specialist physician.
rTMS for OCD
Contributing to the interest in rTMS for OCD is the finding of specific regions of overactivity in the brain. Repetitive TMS is typically administered as add-on therapy for both CBT and drug treatment. Like most OCD treatments, the results from rTMS vary. Some studies have found no clinically important improvement from rTMS (124), while others describe rather satisfactory results. It appears that these results are dependent on the frequency of the magnetic pulse, and the precise location of the coil on the scalp (122, 125). In the case of anxiety disorders, improvement occurs when rTMS is administered over regions of the brain distinctly different from OCD. When rTMS treatment for OCD is applied over the locations used for anxiety, no effect is seen.
The frequency of the energy emitted from the coil also appears to be important. Repetitive TMS at two different pulse frequencies was administered to patients with moderate to severe OCD, and the result tested at the conclusion of treatment and after three months (125). There was a significant (44%) decline of the average Y-BOCS score in the 1Hz group but not the 10Hz or control groups. Other studies show that the degree of improvement from low frequency rTMS varies from study to study, with most in a range from 35% to 40% (126-129). Small and nil effects have also been reported in others (124, 130). The response rates (the percent of treated patients who respond) range from about 30 to 60% (124, 126, 128, 129) although this is not borne out in other reports. Some of the variability between studies may be the result of the criteria used to define response.
Overall, the potential value of TMS as add-on therapy to drug or CBT management is as yet controversial. Current clinical trials of rTMS treatment methods and efficacy will likely better clarify its value. In the meanwhile, significant side effects are very rare, and the options for patients refractory to treatment are limited. Moreover, those who do respond to rTMS appear to have more sustained remissions.
Transcranial Direct Current (or electric) Stimulation
While transcranial direct current stimulation (tDCS) and rTMS are distinctly different methods, both are able to increase (enhance) or decrease (inhibit) neuron activity in specific areas of the brain. Which functional effect occurs depends on how the treatment is set up; in the case of rTMS it is type of magnetic pulse, while tDCS actions are largely dictated by the direction of the delivered current.
Research into the effects of tDCS on brain nerve cell activity has evolved over more than 50 years. From this work, it is now known that weak electrical current can be delivered to the brain through the scalp in order to alter nerve activity. Of great importance is the discovery that placing the anode of the circuit (the positive terminal) over the target area heightens the excitability of the underlying brain, while applying the cathode (the negative terminal) at the site inhibits excitability. Therefore, nerve cell excitability or inhibition can be manipulated by the direction of the current (131). The treatment benefits of tDCS have been tested in a number of diseases among which are depression, fibromyalgia, multiple sclerosis, pain control and Alzheimer’s disease with, at best, mixed results.
tDCS in OCD
Data about effectiveness of tDCS for OCD is rather scant, particularly compared to rTMS. Furthermore, the findings in almost all of the published reports are based on several or fewer patients. However, more and better information may soon be available from several larger and better-designed research studies-in-progress.
Regardless, several anecdotal published reported have interesting findings. One of these described the results of tDCS in two multidrug and CBT-resistant patients with severe OCD (132). It appears that both patients had the mental rituals subtype of OCD in which both had obsessional thoughts with aggressive/harmful and strong sexual themes. The mental compulsions in one were comprised of silent repetitions of prayers. Successful treatment of such patients can be a greater challenge when compared to most other OCD subtypes. Both patients received a course of tDCS while continuing their drug treatment. Their baseline Y-BOCS scores were 25 and 30. Following treatment, both of their scores diminished by around 50%. Notably, one of these individuals, who had been unable to undergo ERP due to extreme anxiety, was able to re-enter CBT following tDCS.
A separate report described tDCS treatment of two patients with multi-treatment resistant OCD (one with symmetry and the other contamination subtype) (133). One of the patients experienced a 45% improved Y-BOCS score that was sustained on re-evaluation six months later. However, the other patient had no significant change. Several other studies report similar findings; there is wide variability of both response and sustainability using tDCS. Also, no patient characteristics have yet been found that help to predict the likelihood of benefit of tDCS as add-on treatment.
Despite the inconsistent findings, tDCS is usually well tolerated, with side effects that include mild headache, and tingling and redness in the area under the electrode. In addition to its good side effect profile, tDCS is also a rather straightforward and comparatively inexpensive method that may be suitable for home use.
Electroconvulsive therapy (ECT)
ECT is a procedure by which a small and precise pulse of electricity is passed into the brain from the scalp. Patients and families’ anxiety or fear when ECT therapy is raised may arise from public perception of it being an archaic procedure. The current ECT protocols are anything but horrifying, although many still remember the images of Jack Nicolson undergoing ECT treatment in the 1975 movie One Flew Over the Cuckoo’s Nest.
Unlike tDCS, ECT effects require that the electrical pulse result in a brief convulsion (seizure). Since those who undergo ECT usually receive general anesthesia and muscle relaxants, the convulsion is not seen physically, but it is monitored using an electroencephalogram (a.k.a. “EEG”) (134). ECT has undergone a substantial amount of research and has been used to treat several types of mental illnesses for decades (134, 135). The procedure results in altered balances of neurotransmitters and/or other chemical substances in the brain. However, it remains unclear how these changes modify clinical symptoms in several mental health disorders (134). Among these, ECT has consistently shown safety and effectiveness in depressive and bipolar disorders and schizophrenia (135, 136).
From a safety standpoint, ECT is considered to be generally safe, but potential adverse effects may occur. There are always risks associated with anesthesia. This risk varies with the type of anesthetics used, ongoing treatment with other drugs, and other individual health problems. This should always be discussed before any procedure that requires anesthesia.
Other possible side effects following ECT include short-term confusion, loss of memory of events occurring days or weeks before the procedure (referred to as retrograde amnesia), and nausea, headaches, or muscle pain immediately following the procedure. ECT safety in recent years was studied in a group of 107 patients who underwent more than 1,000 ECT procedures (137). There were no deaths, life-threatening events, or permanent injuries attributable to ECT. Approximately 67% of patients 60 years old or younger, and 42% of these aged more than 60 experienced no side effects. The most frequent side effect in the younger group was headache (13%), while in the older group it was memory loss (23%). ECT does not cause epilepsy.
ECT in OCD
Largely because of its effectiveness in the treatment of mood disorders, ECT has been used for OCD patients, but quite uncommonly (138). Although some specialists consider ECT to have potential benefit in patients with treatment-resistant OCD (139), there is considerable uncertainty surrounding its direct benefit. There have been no formal studies of ECT in OCD and virtually all of the data is based on case reports or small case series (140). Almost all of the patients in these reports, including those whose OCD symptoms appeared to improve following ECT, had severe and treatment unresponsive conditions. However, the vast majority of these patients also had coexistent and significant mood disorders, mostly depressive (141). Other reports describe improvement of OCD symptoms that often arise in primary bipolar disorder and schizophrenia.
At this time, most clinical scientists believe that there is little evidence that ECT is effective for treating primary OCD (142). The complex relationships between OCD and several other important mental disorders, and the lack of quality data, make conclusions about effectiveness unrealistic. Nonetheless, since experienced specialists can administer ECT with relative safety, it may be an option for those who remain ill despite numerous other therapies.
Deep Brain Stimulation
Like transcranial magnetic and direct current brain stimulation techniques, Deep Brain Stimulation (DBS) uses intermittent signaling to specific brain areas as the method of treatment. In contrast to transcranial procedures, DBS requires a minimally invasive neurosurgical procedure to insert precisely the electrodes into specific locations in the brain. Unlike other and more permanent neurosurgical options, DMS does not destroy brain tissue. This procedure is often described as akin to a heart pacemaker. The high frequency electrical pulses that are transmitted to the electrodes are able to alter specific nerve circuits in the immediately surrounding areas. The locations targeted for optimal electrode placement are selected based on extensive basic and clinical research. The guidance for electrode insertion by the neurosurgeon uses three-dimensional electronic mapping based on imaging studies of the patient’s brain.
DBS has a successful track record for treatment of neurological and neuropsychiatric disorders including Parkinson’s disease, bipolar disorder and depression (143-147). Complications of DBS were documented in a report based on results from more than 30 clinical studies. The most serious complication was bleeding into the brain cavity post-operatively. This occurred in 2.6% of the cases, and some resulted in permanent neurological injury of varying degree (148). Side effects from the DBS procedure were generally reported as minor and transient (148-150). Those often seen include worsening of anxiety, sensing the wires under the skin, flushing and hypomanic symptoms (see 5.1.1).
DBS in OCD
A growing number of DBS studies focus on treating OCD. The typical patient treated with DBS has severe, intractable OCD that has not responded to multiple drug and behavioural therapies. Some also have failed to benefit from transcranial therapies. Short of permanent neurosurgical intervention, this is considered one of the last treatment options. Keeping in mind that DMS is performed in the cases of high severity, the results are quite encouraging (151-153). One representative report summarised the reported DBS outcomes from 25 previously published investigations (149). The averaged results showed:
Patient improvement 55% (includes only those improved by at least 35%)
Y-BOCS score reduction of 43%
Length of follow up 31 months
Thus, DBS appears to be a relatively safe and robust treatment option for OCD non-responders. Several target sites in the brain have shown good results, although the optimal site is yet to be determined.
 Hypomania refers to milder degrees of manic behaviours such as talkativeness, excessively energetic activity, flight of ideas, and risky behaviors.
 In an electrical circuit, the current emerges from the anode, flows through, in this case, the brain, and then completes the circuit by re-entering at the cathode. For example, the power of an ordinary battery results from current emerging from the “+” terminal (the anode), flowing through a device such as a flashlight, and returning to the battery at the “-“ terminal (the cathode).
 Minimally invasive brain surgery in the brain is done through a small hole created in the skull (usually the size of a quarter or less). After navigating to the target site, tiny wires are then threaded under the skin where they are connected to a small pulse generator also under the skin.
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