The choroid plexus (ChP) is attracting attention as a potential aid to the diagnosis, prognosis, and treatment of psychosis. Two recent MRI studies, one published in The American Journal of Psychiatry and the other in Schizophrenia Bulletin, reported greater ChP volume in individuals with psychosis than in controls, and both concluded greater ChP volume may be a marker of inflammatory brain response related to psychosis.

The ChP is the most vital part of the blood–cerebrospinal fluid (CSF) barrier. Together with the glymphatic system, it controls brain homeostasis in general, removes toxic waste, and provides the brain’s clean environment to function optimally.

Because of the size, shape, and location of the ChP, it’s difficult to use automated MRI to determine its volume. In collaboration with 11 institutions worldwide, Researchers at Brigham and Women’s Hospital developed the first MRI manual segmentation method for investigating ChP, and they observed significant ChP enlargement in early-course but not chronic psychosis.

Marek Kubicki, MD, PhD, associate director of the Psychiatry Neuroimaging Laboratory in the Department of Psychiatry at the Brigham, Johanna Seitz-Holland, MD, PhD, of the Psychiatry Neuroimaging Laboratory, Olcay Senay, MD, of the Psychiatry Neuroimaging Laboratory, Magdalena Seethaler, MD, of the Psychiatric University Clinic of Charité at St. Hedwig Hospital, and colleagues report in Human Brain Mapping. The results are preliminary, they caution, but suggest ChP enlargement reflects a neuroinflammatory response that signals disease onset.

Methods

The research team applied their novel method to two independent cohorts:

• 41 individuals with early-course psychosis (mean duration of illness, 1.78 years) and 30 matched healthy individuals

• 30 individuals with chronic psychosis (mean duration of illness, 7.96 years) and 34 matched healthy individuals

ChP Volume

In both cohorts, left and right ChP volumes were higher in individuals with psychosis than in controls. However, the differences were statistically significant only for early-course psychosis.

ChP Volume and Clinical Variables

In individuals with chronic psychosis, there were no significant correlations between ChP volume and total symptom severity. However, left ChP volume positively correlated with total symptom severity close to the significance threshold.

In both data sets, individuals with psychosis were relatively stable clinically, and the narrow range of severity scores might have contributed to the limited findings.

ChP Volume and Lateral Ventricles

Increased lateral ventricle (LV) volumes are a hallmark of psychosis, but in this study, the only abnormality was a significant enlargement of the right LV in early psychosis. The discrepancy from conventional observations is probably related to the relatively small sample.

ChP and LV volumes were positively correlated in chronic psychosis, suggesting ChP enlargement might contribute to LV abnormalities.

Continued Scrutiny Needed

Measurement of ChP volume may one day serve as a way to monitor response to novel diagnostic and therapeutic strategies. More extensive longitudinal studies should analyze clinical factors not explored here (e.g., specific diagnosis, symptom severity, duration of illness, medication, intelligence quotient, smoking, substance use, peripheral inflammation) that could also affect the results.