Myelin staining of deep white matter in the dorsolateral prefrontal cortex in schizophrenia, bipolar disorder, and unipolar major depression

Neuroimaging and postmortem studies suggest the involvement of white matter disease in schizophrenia, bipolar disorder, and unipolar major depression. To date there is no published, collective study of myelin staining in these three psychiatric disorders. Deep white matter lesions, potentially affecting corticolimbic circuits, have been particularly implicated in late life depression and poor outcome bipolar disorder. We hypothesized that individuals with these disorders would manifest reduced deep white matter myelin staining compared to normal controls. Sixty transverse sections of fixed dorsolateral prefrontal cortex - 15 from individuals with each psychiatric disorder and 15 from normal controls - were stained according to the method of Kluver and Barrera. Myelin staining intensity was quantified by digital image analysis and expressed as a percent of grey matter staining for a given section. Mean deep (but not gyral) white matter myelin staining was less intense in all three psychiatric groups compared to control. This difference was statistically significant for the bipolar and unipolar groups, with a strong trend toward attenuated staining in the schizophrenic group. Our findings are consistent with postmortem and neuroimaging studies of affective disorders that indicate an increased prevalence of deep white matter lesions in unipolar and bipolar affective disorders.