['Age-related brain atrophy has been represented by simple 1-dimensional (1-D) measurements on computed tomography (CT) for several decades and, more recently, with 3-dimensional (3-D) analysis, using brain volume (BV) and cerebrospinal fluid volume (CSFV). We aimed to show that simple 1-D measurements would be associated with 3-D values of age-related atrophy and that they would be related to post-traumatic intracranial hemorrhage (ICH).', 'Patients ≥60 years with head trauma were classified with central atrophy (lateral ventricular body width >30 mm) and/or cortical atrophy (sulcus width ≥2.5 mm). Composite atrophy was the presence of central or cortical atrophy. BV and CSFV were computed using a Siemens Syngo workstation (VE60A).', 'Of 177 patients, traits were age 78.3\u2009±\u200910, ICH 32.2%, central atrophy 39.5%, cortical atrophy 31.1%, composite atrophy 49.2%, BV 1,156\u2009±\u2009198 mL, and CSFV 102.5\u2009±\u200963 mL. CSFV was greater with central atrophy (134.4 mL), than without (81.7 mL, p\u2009<\u20090.001). BV was lower with cortical atrophy (1,034 mL), than without (1,211 mL; p\u2009<\u20090.001). BV was lower with composite atrophy (1,103 mL), than without (1,208 mL; p\u2009<\u20090.001). CSFV was greater with composite atrophy (129.1 mL), than without (76.8 mL, p\u2009<\u20090.001). CSFV÷BV was greater with composite atrophy (12.3%), than without (6.7%, p\u2009<\u20090.001). Age was greater with composite atrophy (80.4 years), than without (76.3, p\u2009=\u20090.006). Age had an inverse correlation with BV (p\u2009<\u20090.001) and a direct correlation with CSFV (p\u2009=\u20090.0002) and CSFV÷BV (p\u2009<\u20090.001). ICH was greater with composite atrophy (49.4%), than without (15.6%; p\u2009<\u20090.001; odds ratio\u2009=\u20095.3). BV was lower with ICH (1,089 mL), than without (1,188 mL; p\u2009=\u20090.002). CSFV÷BV was greater with ICH (11.1 %), than without (8.7%, p\u2009=\u20090.02). ICH was independently associated with central atrophy (p\u2009=\u20090.001) and cortical atrophy (p\u2009=\u20090.003).'] Are practical one-dimensional measurements of age-related brain atrophy validated by 3-dimensional values and clinical outcomes : a retrospective study?