Microstructural thalamic changes in schizophrenia: a combined anatomic and diffusion weighted magnetic resonance imaging study

Objective: Several magnetic resonance imaging (MRI) and postmortem studies have supported the role of the thalamus in the pathophysiology of schizophrenia. Interestingly, a recent small diffusion weighted imaging (DWI) study showed abnormal thalamic microstructure in patients with schizophrenia. The objective of our study was to use structural MRI and DWI to explore for the first time both thalamic volumes and integrity in schizophrenia. Methods: We measured thalamic volumes and apparent diffusion coefficient (ADC) measures bilaterally in 71 patients with schizophrenia, representative of those living in the geographically defined catchment area of South Verona (i.e., 100 000 inhabitants), and 75 individuals without schizophrenia. The presence of the adhesio interthalamica was also detected. Results: We found no significant differences in thalamus size between patients with schizophrenia and participants in the control group, with only a trend for decreased left volumes. No abnormal frequency of the adhesio interthalamica was found. In contrast, significantly increased thalamic ADC values were shown in schizophrenia patients. Age significantly inversely correlated with thalamic volumes in both groups and correlated positively with posterior ADCs in patients with schizophrenia. No significant associations between clinical variables and either volumes or ADC values were reported. Conclusion: Widespread altered microstructure integrity and partially preserved thalamus size were found in schizophrenia patients. Therefore, subtle thalamic structural abnormalities are present in schizophrenia, even with maintained volumes. This may result from disruption at the cytoarchitecture level, ultimately supporting corticothalamic misconnection. Future imaging studies should further explore thalamic tissue coherence and its role for cognitive disturbances in patients at high risk for schizophrenia and in first-degree relatives.