High-resolution segmentation of the cavum septum pellucidum in young adult human brains

Andew Rios¹Achok Alier¹Mihir Aneja¹Farah Nimeri¹Kayla Lavery¹Jack Fisher¹Rochana Wiyathunge¹Edward Yeterian²Marek Kubicki^3,4,5,6Sylvain Bouix⁷Nikos Makris^5,6,8,9Hector Arciniega^10,11Richard Jarrett Rushmore^1,5,6,8*

• ¹Department of Anatomy and Neurobiology, Chobanian & Avedisian School of Medicine, Boston University, Boston, Massachusetts, United States
• ²Department of Psychology, Colby College, Waterville, Maine, United States
• ³Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States
• ⁴Department of Psychiatry, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States
• ⁵Psychiatric Neuroimaging Laboratory, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, United States
• ⁶Center for Morphometric Analysis, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States
• ⁷Département de génie logiciel et des technologies de l'information,École de Technologie Supérieure, Montreal, QC, Canada
• ⁸Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States
• ⁹Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States
• ¹⁰Department of Physical Medicine & Rehabilitation, Grossman School of Medicine, New York University, Mineola, New York, United States
• ¹¹Langone Medical Center, New York University, New York City, New York, United States

The cavum septum pellucidum (CSP) is a small cerebrospinal fluid-filled space found between the lateral ventricles of the forebrain that is often used as a biomarker for neurological disease and brain injury. The incidence of the CSP varies widely in different studies, with many reports finding that the CSP is frequently absent in healthy brains. Variables such as race, age and sex are typically not well reported in CSP studies, presenting a challenge to understanding the normal distribution of the CSP in adult human brains. Moreover, the small size and frequently indistinct borders present a challenge for automated segmentation of the CSP. To address these issues, we developed a novel manual parcellation approach to volumetrically segment the CSP in high-resolution T1weighted structural MRIs from male and female participants in the young adult dataset of the Human Connectome Project (HCP). We identified the CSP in 95.6% of subjects, compared to 57.1% when the automated segmentation approach was used on the same subjects. The CSP volume was significantly larger in male than female brains, both in terms of raw volume and volumes normalized for intracranial volume. To our knowledge, this study is the first to develop and validate a segmentation protocol for CSP volume, and to evaluate both the incidence and volume of the CSP in a representative population of young adults. Overall, these results provide a more accurate representation of the CSP in control populations, laying an improved foundation for its potential use as a biomarker for various disorders.