Reduced thalamic volume in patients with chronic schizophrenia after switching from typical antipsychotic medications to olanzapine.

OBJECTIVE The authors performed a longitudinal study of the effects on thalamic volume of switching from typical to atypical antipsychotic medications. METHOD Magnetic resonance imaging scans were acquired from 10 subjects with chronic schizophrenia taking typical antipsychotics and 20 healthy volunteers. Subjects with schizophrenia were switched to olanzapine; both groups were rescanned. RESULTS At baseline, thalamic volumes in subjects with chronic schizophrenia were 5.8% greater than those of healthy volunteers. At follow-up, there was no significant difference between groups. Additional analysis revealed a significant positive correlation between baseline thalamic volume and dosage of typical antipsychotic medication. Higher dosages at baseline were correlated with larger reductions in volume after the switch to olanzapine. CONCLUSIONS Antipsychotic medication effects may be a factor in the wide range of thalamic volume differences reported between subjects with schizophrenia and healthy volunteers.