Auditory hallucinations, as a primary symptom of schizophrenia, can be a main target of antipsychotic treatment. However, up to 40% of patients have only a partial response to medications. As such, there has been extensive exploration of the neurocognitive basis of auditory hallucinations. Neuroanatomical and imaging studies in these 'treatment-resistant' patients have demonstrated hyperactivity in the left temporo-parietal cortex.[13,14] By exploiting its inhibitory role, when applied at low frequencies, an rTMS protocol delivered at 1 Hz to the posterior superior temporal gyrus (STG). Hoffman et al. were able to demonstrate a reduction in auditory hallucinations after application to this speech processing cortex. Moreover, a subsequent study by the same group demonstrated sustained improvement 15 weeks after treatment in many of the subjects.
Other groups targeted different anatomical areas likely to be involved in the genesis of auditory hallucinations. Unfortunately, results of treatment studies have not been robust. It should be noted that the majority of rTMS treatment studies have centered on subjects with medication-resistant auditory hallucinations. Very little is known about the treatment effect rTMS would have for antipsychotic-responsive subjects.
Lastly, a recent meta-analysis by Slotema et al. examined 7 rTMS randomized controlled trials (RCTs) with a total of 189 schizophrenia subjects who were experiencing pervasive auditory hallucinations. One hundred and five subjects received active rTMS treatment and there was a moderate effect size of 0.54, with only an 8.6% occurrence of side effects. While this was a somewhat smaller effect size than a previous meta-analysis, the clear recommendation remains for rTMS as treatment of auditory hallucinations in schizophrenia: specifically in treatment-resistant patients.
Expert Rev Neurother. 2013;13(10):1079-1082. © 2013 Expert Reviews Ltd.