Treatment resistant depression and the role of repetitive Transcranial Magnetic Stimulation (rTMS)
Major depression remains the most prevalent of mental disorders. The economic impact of this mental health condition on productivity has been determined to be in the scale of billions per year. At a clinical level, optimising the treatment of Depression for a particular individual remains a difficult task. Therapeutic treatments for depression can be broadly categorized as psychotherapeutic or talk therapy, pharmacological or medications and neurostimulation or direct stimulation of the brain. It is estimated that about 50% of patients receiving medication treatment for depression do not recover (Lefraucheur, 2020) and this is termed Treatment Resistant Depression.
Transcranial Magnetic Stimulation (TMS) is a procedure whereby an electromagnetic coil placed against the scalp creates a magnetic field that stimulates certain areas of the brain.
There has been considerable research into the efficacy of magnetic stimulation of human brain since Barker et al published their findings in 1985 (Barker, Jalinous, & Freeston, 1985). It has been established that excitability of human brain can be changed temporarily through single pulse magnetic stimulation and for extensive periods of time using repetitive magnetic stimulation or rTMS.
Magnetic stimulation machines can be programmed to deliver high frequency repetitive stimulation or low-frequency repetitive stimulation to a targeted area of the brain. A major advantage in using magnetic stimulation is that it can be done when the individual is fully awake and no anaesthesia is required. Stimulation of brain through rTMS does not require seizure for therapeutic effect, making it significantly safer than Electro Convulsive Therapy (ECT) where electric current is used to stimulate the brain. Evidence from functional imaging of the brain indicates that rTMS causes alteration in blood flow to the brain, changes the metabolism of targeted brain areas and produces neurochemical changes that are postulated to have antidepressant effect (Kelner, 2012).
Clinical practice indicates that rTMS is usually very well tolerated by patients and can be given concurrently with antidepressant medications in most patients. Present recommendations favour the use of this treatment modality for Major Depression when adequate response has not been achieved through judicious use of pharmacotherapy. rTMS provides a form of brain stimulation that is not associated cognitive impairment or other serious side effects or anaesthesia and it is likely to become a mainstream treatment option especially after recent endorsement by Medical Services Advisory Committee (MSAC) for Medicare subsidy which is likely to come through in near future.
References
(Barker, Jalinous, & Freeston, 1985) (Kelner, 2012) (Lefraucheur, 2020)