Introduction: schizophrenia (SCH) is a heterogeneous syndrome characterized by positive and negative symptoms. Despite appropriate medication, about 1/4 of patients suffer for refractory positive and/or negative symptoms, which are associated with functional handicap, increase of duration and of the number of hospitalizations. Numerous studies have suggested that the pathophysiology of auditory hallucinations (AH) is related to a hyper activity of the left temporoparietal cortex (TPC). On the other hand, negative symptoms are associated with a prefrontal hypoactivity and the efficiency of pharmacological treatments is frequently partial. Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation tool with excellent tolerability and safety. Given its hypothesized mechanisms of action and the clinical beneficial effects obtained in several types of pathology (Aleman et al. 2007), the efficacy of rTMS has been investigated for drug-resistant SCH symptoms.
Objective: our objective is to expose the knowledge concerning the rTMS use in the treatment of these symptoms and to purpose a critical analysis of these data.
Method: a systematic review of the literature has been conducted using NIH Pubmed. The following search terms were used: TMS - rTMS - Schizophrenia - negative symptoms - hallucinations.
Results: concerning the treatment of AH, 16 publications and 4 meta analyses were selected. For the negative symptoms, we retained 16 studies and 3 meta analyses. The most extensively investigated application for rTMS in SCH is the use of low-frequency stimulation to the left TPC with the aim to improve AH symptomatology. When compared to sham, this type of acute course of rTMS has been proven to induce a substantial and significant reduction in AH. But this effect does not seem long-lasting and maintenance protocols must be developed. Concerning negative symptoms, the results are less solid but we find some works which demonstrate an improvement of these symptoms while various stimulation parameters were used. Recently, new parameters of stimulation in particular the theta burst stimulation have permitted us to obtain larger effects with longer duration. The interest of these new parameters will be discussed here.
Conclusion: overall, rTMS studies have demonstrated some promise in the treatment of SCH. However, more research is required to enhance rTMS efficacy and increase its beneficial effect duration and to test new therapeutic strategies in this topic.