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.