วันศุกร์ที่ 30 ธันวาคม พ.ศ. 2554

Transcranial Magnetic Stimulation , New Treatment Option for Depression



               Depressive disorder is a mental disorder which has deterious effects to individual life, family and to the society at large and depression would be a disease burden much more than many physical diseases. From the past to the present, the diagnosis and treatment of depression are still have some limitations. Also this is a challenging issue in psychiatric treatment.






Depressive disorder or depression is an infrequent condition which can be occurred in every population throughout the world. The community survey yield the ne-year prevalence of 3-11 % in adults, 8 % in children and 22 % in the elderly. From the Global Burden of Disease Study (GBD) reported by Murray and Lopez in The Lancet 1997, predicted that depression will be in the second rank of disease burden just lower than coronary artery disease, and even higher than the injuries from traffic accidents.



Depression is a chronic condition which can relapse and recurrent eventhough the patients are being treated. Moreover, 1 in 3 are classified as treatment-resistant depression(TRD) when there have no adequate response after 2 courses of different antidepressant medications. This is still be a major concern in treating depression. Therefore, many researchers worldwide are trying to find a more effective treatments for this group of patients.


The main clinical features of depressed patients are depressed mood, loss of interrest and pleasure to do anything, being despair , difficulty to accomplish even the household or routine works. These symptoms will be concomittant with anorexia, weight loss, insomnia or frequent awakening, fatique and loss of energy, memory loss and impaired concentration , inability to make a decision even the trivial issue, decrease libido or loss of sexual interest, feeling guilty ,thought about death and suicidal ideations. Many depressed patients commited suicide during this period. All of these symptoms are pervasive which occur throghout the days and continue everyday for at least 2 weeks. The illness cause impairment of functions in daily living and affected the whole family life too.


Depression is a disorder of co-morbidity which means that any individual who depressed has a tendency to have another psychiatric disorder such as substance use disorder, anxiety disorders which will inevitably complicated and worsening the conditions. Depression can occur in patients with physical illness. We have found 26% in longterm hospitalized patients, 50% in Parkinson's disease patients and 33% in stroke victims. Twenty-seven percent of diabetes who has to be treated by oral or injected medications and need regular blood check which cause trouble and emotional stress, got depressed.



What causes depression?

The exact etiology of depression still be unknown. Many researchers explained the illness by using the bio-psycho-social model. The interaction of brain, mind and the environment in specific cultural and religions are very complicated issues. However, the functions of brain are more extensively studied during the past. There are some relevant findings which underlie the cause of depression.


Start with the decreasing level of neurotransmitters serotonin, noradrenaline, dopamine in the brain which can be corrected by antidepressant drugs. However, this hypothesis can not explain the delay of 3-6 weeks before the effectiveness of drugs occur. In additions, we also found the abnormalities of hormonal system, sleep pattern not just the neurotransmitter system.



The next hypothesis is about the generation and development of neural tissue which composed of neuron and glial cell by "brain plasticity process". Brain-derived neurotrophic factor(BDNF) is a neuropeptide responsible to neurogenesis, decreasing in depressed patients and will be normalized after the antidepressants treatment. The new neuron and supporting cells work together to make a feeling of wellness , joyfulness , good concentration , a better thoughts and memory.


From the advancement of neuroimaging which help seeing the brain functionings in real time such as functional MRI, Single photon emission tomography (SPECT), Positron emission tomography(PET) scan. We discovered that during depression, the left anterior frontal lobe so called dorso-lateral prefrontal cortex (DLPFC) decrease its activity while the ventro-medial prefrontal cortex(vmPFC) and right prefrontal cortex have increased activity and send the inhibitory impulses to the left which markedly reduce functions of the left-sided brain,


The prefrontal lobe is the most developed brain in human. Dysfunctioning of this part will impede various brain activity. In this viewpoint, depression can be viewed as a brain disorder. The DLPFC responsible for attention, concentration, planning and decision making, while excess function of VMPFC reponsible for negative emotions, depression and anxiety with the interference from the right brain too.



Treatment with Transcranial Magnetic Stimulation

Basic of TMS is to send electromagnetic pulses into the specified brain area to induce the secondary current in the underneath neural tissue. When repeatedly stimulate , the brain will be modulated both in terms of stimulation or inhibition depends on the frequency of TMS pulses. When apply with the low frequency (<=1 Hz.) the neural network will be inhibited, but when apply the rapid or high frequency(>= 5Hz.) the neural network activities are enhanced. Therefore, we can choose to stimulate the low activity left side while inhibit the excess function right side in treating depression. There are many studies confirming the use of TMS for neurologic and psychiatric disorders. The most prominent one is TMS for treatment of depression. When summarized the results from well designed studies, TMS is effective in acute depression comparable to drugs but less side-effect. TMS can be used as stand alone or to augment the effect of drugs in treatment resistant cases. The US Food and Drug Association and many countries such as Canada, Isarael, Brazil, EU countries have already approved the use of TMS in treating depression.


TMS also gains its increasing role in maintenance treatment of depression to prevent relapse, recurrent and waiting to further confirmatory studies. Some hospital applied TMS one or twice a week for 2-3 years and found a very promising result to prevent another episodes of illness.



The benefit of Transcranial Magnetic Stimulation

TMS is safe because it is a non-invasive brain stimulation. The brain do not exposed to electric current directly as in Electroconvulsive Therapy. No need of anesthesia , no seizure induction. TMS do not interfere memory and learning, on the contrary, many patients gain their cognitive abilities including memory after treatment with TMS. Patients don't need to be hospitalized and they drive back home by themselves.


The process of TMS

Start with determining the sites and optimum stimulation parameter for each individual which is varied. The special designed figure-of-eight coil will be placed at the site. The patiens will be asked to sit comfortably still on recliner for 20-30minutes. The treatment can be applied once or twice a day depends on tolerability of patients. Before treatment , no specific preparation are required (foods , beverages , medications can be used as usual) . Our trained staff will attend the patients throughout the process. Patients can talk with staffs, relatives, friens freely during treatment. Any questions are welcome.


Contraindication and precautions
TMS can not be used in patients with intracranial metallic implants including cochlear implant.


Special precautions will be applied for the epileptics because TMS can induce seizure in this patient group 1.4 %. The risk of induced seizure in non-epileptic is very low.


TMS can induce mania or hypomania in bipolar individuals like most of antidepressant treatment. The doctors have to evaluate and monitor both before and after treatment.


Side effects and safety
Transcranial magnetic stimulation was considered safe and had no serious side-effects. The minor side effects might occur such as headache and pain at stimulation site which are just temporary.


No adverse effects on memory and concentration. As mentioned before. Many patients experienced improvement of memory and concentration after TMS course. This might be from the alleviation of depressive symptoms or TMS directly stimulate the function of prefrontal cortex which responsible for learning, planning, memory and decision making.


The cost effectiveness of TMS In the USA, there are economic studies which compare the expense of treatment and cost of depressive illness. The illness cost including disabilities in works, family, social, self care which are the indices of quality of life. TMS is a cost effective treatment especially in medication resistant cases which need to try many expensive antidepressants and prolong course of illness.

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