Transcranial Magnetic Stimulation (TMS) in Schizophrenia

Until recently stimulation of nervous tissue deeper than approximately 2 cm from the scalp (will hence be called non-deep TMS) was not possible (3).A new coil ("H"-coil invented in Weizmann Institute of Science, Neurobiology Department, Rehovot, Israel ) capable of stimulating more than twice this depth (Up to 5 cm)was recently developed.Deep TMS is using this h-coil.

Auditory hallucinations are reported by 50% to 70% of patients with schizophrenia and generally consist of spoken speech or "voices." . Patients usually describe the hallucinatory experience as distressing, consistent with evidence that the most common hallucinated utterances are abusive terms,contributing in up to 25% of the cases to a serious suicide attempt.The neuroanatomical basis of auditory hallucinations is thought to involve increasing blood flow of the speech perception areas of the brain, such as the superior temporal cortex of the dominant hemisphere as well as right and left superior temporal cortex.Brain imaging studies of patients with auditory hallucinations have revealed an active area in the right and left superior temporal cortex, Broca's area, and the left temporoparietal cortex. Shergill et al. reported the presence of active areas in the anterior cingulate cortex, right thalamus, left hippocampus, and parahippocampal cortex when subjects were experiencing auditory hallucinations.

Magnetic Stimulation of Left Temporoparietal Cortex suggest that the mechanism of auditory hallucinations involves activation of the left temporoparietal cortex.Reasons to believe that right frontotemporal TMS stimulation cortex can ameliorate auditory hallucinations include evidence that right temporoparietal stimulation achieved significant changes in the frequency of auditory hallucinations,in the patients with auditory hallucinations an increase in blood flow is noted in the right superior temporal gyrus,right temporal lobe activation during auditory hallucination,effect of rTMS can spread to the opposite hemisphere through interhemispheric connections,some evidence that brain circuits involved in the production of auditory hallucinations and symptoms of schizophrenia are widespread and not confined in the left temporoparietal cortex.Deep TMS can reach brain structures as deep as 5 cm whereas non-deep TMS can reach structures less than half that distance. As deep brain structures such as thalamic, limbic and paralimbic regions have been shown to be activated during auditory hallucinations and suspected to play a role in the pathogenesis of auditory hallucinations, their stimulation may attenuate auditory hallucinations. Non-deep TMS can stimulate the cortex but not the neuronal pathways connecting it to deeper brain structures and which stimulation may be additive.