The importance of neuronal interactions in development, the cortical dependence of many thalamic nuclei, and the phenomenon of transsynaptic degeneration suggest possible abnormalities in thalamic nuclei with connections to other brain regions implicated in schizophrenia. Because frontal and temporal lobe volumes are diminished in schizophrenia, volume loss could characterize their primary thalamic relay nuclei (mediodorsal nucleus [MDN] and pulvinar).
Tracers delineated the thalamus, MDN, and pulvinar on contiguous 1.2-mm magnetic resonance images in 12 schizophrenic patients, 12 with schizotypal personality disorder (SPD), and 12 normal control subjects. The MDN and pulvinar were rendered visible by means of a Sobel intensity-gradient filter.
Pixel overlap for delineation of all structures by independent tracers was at least 80%; intraclass correlations were r = 0.78 for MDN and r = 0.83 for pulvinar. Pulvinar volume was smaller in schizophrenic (1.22 ± 0.24 cm3) and SPD (1.20 ± 0.23 cm3) patients than controls (1.37 ± 0.25 cm3). Differences for MDN were not statistically significant; however, when expressed as percentage of total brain volume, pulvinar and MDN together were reduced in SPD (0.14%) and schizophrenic (0.15%) patients vs controls (0.16%). Reductions were more prominent in the left hemisphere, with MDN reduced only in the schizophrenic group, and pulvinar in both patient groups. Total thalamic volume did not differ among the 3 groups.
Measurement of MDN and pulvinar in magnetic resonance images is feasible and reproducible. Schizophrenic and SPD patients have volume reduction in the pulvinar, but only schizophrenic patients show reduction relative to brain volume in MDN.