A study of efficacy and outcome of rTMS in Somatic symptom disorder with predominant pain- single blind randomized controlled trial

According to the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders Somatic symptom disorder (SSD) is defined as distressing somatic symptoms combined with excessive or maladaptive thoughts, attitudes, and behaviors. Patients with somatic symptom disorder repeatedly presents with physical symptoms and persistently request medical examinations, despite being assured that the symptoms are not physical in nature and getting no findings in investigations. SSD with a global prevalence of 5–7%, causes significant distress and disrupts social functioning of the patient.

In SSD with predominant pain there is hyperactivity of the dorsal anterior cingulate cortex and in the anterior part of the insula that are controlled by the Dorsolateral prefrontal cortex (DLPFC) by pain control network. Neurophysiologic activity of the focal targeted area that are involved in the pathophysiology of SSD can be modulated by Repetitive Transcranial Magnetic Stimulation(rTMS) which is a safe and non-invasive technique.Studies were done on fibromyalgia which is characterised by widespread persistent musculoskeletal pain and applying high or low frequency rTMS on these patients over DLPFC significantly improves the patient symptom. Somatic symptom disease with predominant pain is similar in the clinical presentations and distribution to the fibromyalgia.

RATIONALE OF THE STUDY

Even though there have been studies exploring the effects of rTMS in resistant depression, acute management of major depression and in obsessive compulsive disorders but there are only few studies exploring outcome and efficacy of rTMS in somatic symptom disorder with predominant pain. These studies have showed positive results. There have been very few studies from India and major short comings were smaller sample size. Also, these studies lacked in active comparator. In our study, we plan to assess outcome and efficacy of rTMS in somatic symptom disorder with predominant pain and also comparing it to sham rTMS in control group. rTMS being a new advanced treatment modality which is non- invasive and helps in management of cases of resistant depression and OCD, can become a useful technique in otherwise difficult to treat and management of somatic symptom disorder (SSD) with predominant pain.

rTMS PROTOCOL

In this intervention real and the sham rTMS will be applied by stimulating the target area dorsolateral pre frontal cortex by figure of eight coil at frequency of 10 Hz by the Magstim rapid2 machine at 100 percent of the calculated resting motor threshold. Resting motor threshold will be calculated by giving the lowest stimulating intensity to the abductor pollicis brevis muscle by taking 8 trials out of it in 4 trial the motor evoked potential should be greater than 50 Mv. After that figure of eight coil will be placed 5 cm anterior to the optimal motor point area that is primary motor cortex and after locating the Dorso-lateral prefrontal cortex pulses of 30 trains of 40 stimuli each and an intertrain interval of 26 seconds will be delivered.

METHODOLOGY

Study participants will be chosen from patients visiting Psychiatry OPD AIIMS Raebareli on Monday to Saturday. Diagnosis will be made by consultant in charge based on structured clinical interview and according to the Diagnostic statistical manual of mental disorders 5th edition [DSM-5]. Patient not improving on conventional treatment that includes pharmacological or psychotherapy interventions shall be included in the study after written informed consent regarding the details of study. After diagnosis and selection criteria is met, participants will be divided into two groups by computer generated random number table - intervention and Sham control group. Detailed sociodemographic, clinical and anthropometry of each subject will be recorded as per case record format. Patient pharmacotherapy and medicines will be continued as advised.

Subjects condition will be then assessed using the 15-questionnaire related to patient health (PHQ 15), an instrument that can be self-administered by patient to screen for SSD (Somatic symptom disorder) and scale for pain. Hamilton rating scale for depression and Hamilton rating scale for anxiety will be applied.

Both the group will be then introduced about rTMS repetitive Trans cranial magnetic stimulation, daily regimen of high frequency rTMS will be administered to the intervention group, targeting the dorsolateral prefrontal cortex by calculating the resting motor threshold. Total 15 sessions will be conducted and subject will again be assessed for improvement after 6th, 10th and 15th session and for the sham group we will use the sham coil.

The changes in PHQ 15, NRS and subjective improvement in symptoms will be defined as primary outcome and changes in HAM-D and HAM-A scores following intervention will be taken as secondary outcomes. An independent t test will be applied to analyse for any significant changes in treatment arms between the intervention and the control group. patient shall be thanked for participation and provided with the report, if desired. Data analysis will be carried out using appropriate data tools and statistical tests.