Should repetitive Transcranial Magnetic Stimulation (rTMS) be considered an effective adjunctive treatment for auditory hallucinations in patients with schizophrenia?

Abstract

The experience of auditory hallucinations, especially verbal hallucinations, is a common psychotic symptom in persons with schizophrenia, but in about 30% of these individuals traditional treatment with antipsychotic medication is not effective in reducing the hallucinations. For this subgroup of patients, alternative forms of treatment need to be assessed. The occurrence of auditory hallucinations has been linked to abnormal activation or inhibition of the neural circuits related to language processing, especially those in the left temporoparietal lobe. [1] Repetitive Transcranial Magnetic Stimulation (rTMS) is a noninvasive method that adjusts the excitability of the cortex, so rTMS is one type of adjunctive treatment for medication-resistant auditory hallucinations in schizophrenia that researchers have been interested in. Hoffman and colleagues [2] first reported the possibility of using rTMS to treat auditory hallucinations in 1999. There have been at least 18 sham-controlled studies that reported the effectiveness and safety of rTMS in the treatment of auditory hallucination; the majority were randomized sham-controlled trials and a minority used a cross-over design. Most participants in these studies had intractable auditory hallucinations. Low stimulation frequencies (e.g., 1Hz) were used with a strength ranging from 80 to 115% of the participant’s motor threshold. The most common site of stimulation was the left temporoparietal junction (T3P3); other sites include the right temporoparietal junction (T4P4), the left or right Wernicke areas, and individualized sites determined by fMRI. The total number of pulses ranged from 240 to 4200 for a single treatment session. The duration of rTMS treatment was usually between one and four weeks. [3] All of these studies were small-scale; only three had 20 or more participants (in each arm of the study) and none of them had more than 30 participants. Three studies published in Biological Psychiatry in 2005, 2011, and 2013, reflect the evolution of scientific thinking about rTMS as an adjunctive treatment for auditory hallucinations in schizophrenia. Hoffman and