S195. ROLE OF BOOSTER SESSION TRANSCRANIAL DIRECT CURRENT STIMULATION (TDCS) FOR PERSISTENT AUDITORY HALLUCINATIONS IN SCHIZOPHRENIA

BACKGROUND: Auditory verbal hallucinations (AH), one of the hallmark symptoms, are present in 60–80% of schizophrenia (SZ) patients. 25% of patients suffering from AH in schizophrenia fail to respond to any psychotropic medication. Non-invasive brain stimulation techniques like transcranial direct current stimulation (tDCS), with cathodal electrode placement on the left temporoparietal junction (TPJ) is known to alleviate such symptoms in SZ. In this study, we describe the effects of booster tDCS after relapse of AH in patients. The pattern and effectiveness of booster treatment cycles for alleviation of AH in a naturalistic clinical setting are explored in this study. METHODS: Patients with persistent AH (n=15) received an initial course (cycle) of add-on tDCS with cathode at left TPJ and anode over left dorsolateral prefrontal cortex (L-DLPFC) with 2mA current, twice-daily 20-minute sessions for 5 days with intersession interval of 3-hours. Clinical global impression- improvement scale (CGI-I) was rated at the end of the course for every patient. All the patients who were found to show response (“much improved” and “very much improved”) received repeat cycles of add-on booster tDCS after a varying duration ranging from 1–32 months from initial treatment course, due to relapse/persistence of AH. Thirteen out of fifteen patients received one booster cycle while one patient received 3 booster cycles and another received 12 booster cycles. We conducted a spearman’s rank correlation test to determine the correlation between CGI-I score rating at the end of add-on tDCS, and the duration of maintenance of improvement before relapse/ worsening of AH. RESULTS: Six of the fifteen patients (40%) had responded “very much improved” and nine (60%) patients had responded “much improved” to tDCS in the initial cycle. It was found that 50% of the initial “very much improved” responders (n=3) had a comparable response to tDCS after booster sessions for relapse of symptoms while 50% of patients showed “much improved” (n=2) and “minimally improved” (n=1) response in the booster sessions. Among the nine patients who showed “much improved” response from the initial cycle, one patient showed better response than initial cycle (“very much improved”) to booster session. Five patients showed “minimally changed” response in the second cycle in the booster sessions while three patients had comparable responses. The average duration of symptom free interval/ maintenance of improvement with initial cycle of tDCS was found to be 10.46± 9.23 months. The CGI improvement from the initial add-on tDCS course and the duration of the maintenance of improvement/symptom-free interval before the booster session was not found to be significantly correlated (r=0.332, p=0.226) DISCUSSION: A reduction in hallucinations was noted with booster tDCS in patients who had responded to the initial course of add-on tDCS. Booster tDCS is a feasible option and given its cost-effectiveness and ease of administration, booster sessions of tDCS can be considered for resurgence of symptoms. Future studies are recommended in systematically exploring maintenance tDCS as an add-on treatment for persistent/recurring AVH in schizophrenia.