To the Editor: In February 2011, a 44-year-old man with schizophrenia was referred to our hospital for the treatment of auditory verbal hallucinations. He had undergone outpatient treatment with adequate dosages of antipsychotic medications for several months, but he still heard a real-sounding voice that ordered him to commit suicide. We introduced transcranial direct current stimulation (tDCS) as a novel therapeutic approach. Cathodal stimulation diminishes cortical excitability at a circumscribed region (1), and Wernicke's area has been described as an appropriate target region for cathodal stimulation in previous transcranial magnetic stimulation (TMS) studies (2—4). The anodal electrode was placed over the right supraorbital area.

Transcranial direct current stimulation was applied for 15 minutes on 10 consecutive days by using a 1 mA current and 7 cm × 5 cm electrodes, resulting in a current density of 0.029 mA/cm². The medication doses (5 mg of haloperidol and 20 mg of olanzapine) remained the same 4 weeks before and during the patient's intervention. Before and after tDCS, we measured arterial spin labeling, a noninvasive MR technique that provides a direct quantitative measure of cerebral blood flow (CBF). Arterial spin labeling has been successfully used to measure the difference and changes in regional CBF between healthy individuals and schizophrenia patients experiencing formal thought disorders (5). Clinical assessments showed improvements in our patient's scores on the Hallucination Change Scale (pre-tDCS score=10; post-tDCS score=4), the Positive and Negative Syndrome Scale (pre-tDCS score=61; post-tDCS score=50), and the Psychotic Symptom Rating Scale (pre-tDCS score=51; post-tDCS score=43). The decrease in regional CBF indicated that the intervention had a specific neurobiological effect (Figure 1). At follow-up investigation 6 weeks after the tDCS intervention, our patient's clinical improvement was maintained.

To our knowledge, this is the first case report suggesting the clinical and neurobiological efficacy of cathodal tDCS in the treatment of auditory verbal hallucinations in a patient with schizophrenia. Compared to TMS, a rather expensive and laborious technique, tDCS is convenient and inexpensive, and the equipment is highly portable. It could be an attractive treatment option for alleviating long-term hallucinations in the clinical setting. Although the findings are promising, further study of tDCS for this clinical indication is required.