Relatives of schizophrenia patients show cortical thinning

By Mark Cowen, Senior medwireNews Reporter

Patients with schizophrenia and their unaffected relatives show significant cortical thinning compared with mentally healthy individuals without such a family history, researchers report.

Furthermore, in both schizophrenia patients and their relatives, the team found an association between cognitive dysfunction and reduced thickness of the frontal cortex, and between predisposition to hallucinations and reduced thickness of the superior temporal gyrus.

"Our findings are relevant for neurodevelopmental models of schizophrenia and indicate new quantitative trait loci for association studies that explore the genes that confer vulnerability to abnormal brain development in schizophrenia," write Viola Oertel-Knöchel (Johann Wolfgang Goethe-University, Frankfurt, Germany) and team in Cerebral Cortex.

The researchers used magnetic resonance imaging to assess cortical thickness in 25 patients with schizophrenia, 29 of their first-degree relatives, and 37 age-, gender-, and parental education-matched mentally healthy controls without a family history of schizophrenia.

Compared with both relatives and controls, schizophrenia patients showed significant cortical thinning in the inferior frontal gyrus bilaterally, the left superior temporal gyrus (Brodmann's area 41), and the right lingual gyrus. Cortical thickness values in these areas did not differ between relatives and controls.

Compared with controls, both patients and relatives showed significantly reduced cortical thickness in the middle frontal gyrus bilaterally, the left precentral gyrus, the right superior temporal gyrus, the left inferior parietal lobule, the right insula, the left anterior cingulate, the hippocampus, and the parahippocampal gyrus. Thickness values in these areas did not differ between patients and relatives.

The team also found significant differences in cortical thickness among all three groups in the right inferior frontal gyrus, the right precentral gyrus, the middle temporal gyrus bilaterally, and the superior parietal lobule bilaterally, with cortical thickness values in relatives being mostly intermediate between those of patients and controls.

In both patients and controls, lower subjective cognitive function, as assessed using the Eppendorf Schizophrenia Inventory, was associated with reduced thickness of the frontal cortex.

Furthermore, predisposition to hallucinations, as assessed using the Revised Hallucination Scale, was associated with reduced thickness of the superior temporal gyrus in both patients and relatives.

Oertel-Knöchel et al conclude: "The main finding of the present study was widespread cortical thinning in unaffected relatives of patients with schizophrenia compared with healthy matched controls.

"These were largely intermediate to the differences found between patients and controls, suggesting the possibility that they constitute an endophenotype of the disorder."

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