PET and MRI of the thalamus in never-medicated patients with schizophrenia.

OBJECTIVE

This study reports the first paired measurements of glucose metabolism and size of thalamic regions in never-medicated schizophrenic patients using coregistered magnetic resonance imaging (MRI) templates.

METHOD

Positron emission tomography with [18F]fluorodeoxyglucose and matching MRI scans were obtained in 20 never-medicated patients with schizophrenia and 15 normal volunteers. Methods for thalamic edge finding, statistical testing of shape differences with chi-square maps, and MRI localization of major thalamic subregions were developed.

RESULTS

Patients with schizophrenia showed a diminished metabolic rate in the right thalamus, with a loss of the normal pattern of right greater than left asymmetry. Division into anterior/posterior segments revealed that the left anterior and right posterior showed the decrease. Differences were greater for metabolism in the weighted thalamic area (ratexarea) than for rate per unit area, a finding consistent with reported greater decreases in total neuron number than of neuron density in the thalami of schizophrenic patients. The area of the thalamus was smaller in the patients than in the volunteers, and this difference was greatest in the left anterior region.

CONCLUSIONS

The reduced thalamic activity observed in this study lends further support to the concept of deficits in sensory filtering in schizophrenia.