Hippocampal volume is reduced in schizophrenia and schizoaffective disorder but not in psychotic bipolar i disorder demonstrated by both manual tracing and automated parcellation (FreeSurfer)

Abstract

This study examined hippocampal volume as a putative biomarker for psychotic illness in the Bipolar-Schizophrenia Network on Intermediate Phenotypes (B-SNIP) psychosis sample, contrasting manual tracing and semiautomated (FreeSurfer) region-of-interest outcomes. The study sample (n = 596) included probands with schizophrenia (SZ, n = 71), schizoaffective disorder (SAD, n = 70), and psychotic bipolar I disorder (BDP, n = 86); their first-degree relatives (SZ-Rel, n = 74; SAD-Rel, n = 62; BDP-Rel, n = 88); and healthy controls (HC, n = 145). Hippocampal volumes were derived from 3Tesla T1-weighted MPRAGE images using manual tracing/3DSlicer3.6.3 and semiautomated parcellation/FreeSurfer5.1,64bit. Volumetric outcomes from both methodologies were contrasted in HC and probands and relatives across the 3 diagnoses, using mixed-effect regression models (SAS9.3 Proc MIXED); Pearson correlations between manual tracing and FreeSurfer outcomes were computed. SZ (P =.0007-.02) and SAD (P =.003-.14) had lower hippocampal volumes compared with HC, whereas BDP showed normal volumes bilaterally (P =.18-.55). All relative groups had hippocampal volumes not different from controls (P =.12-.97) and higher than those observed in probands (P =.003-.09), except for FreeSurfer measures in bipolar probands vs relatives (P =.64-.99). Outcomes from manual tracing and FreeSurfer showed direct, moderate to strong, correlations (r =.51-.73, P