Craniometric measures of microcephaly using MRI

BackgroundMicrocephalic brains exhibit varying sizes, shapes, and dimensions when compared to normocephalic counterparts, but the extent of these differences is unresolved.AimsTo ascertain developmental changes in brain morphology using craniometric (linear brain) measures derived from MRI in microcephalic individuals and in normocephalic controls.Study designA retrospective, cross-sectional cohort study.SubjectsTwenty-one primary and secondary microcephalic individuals ages 2 postnatal weeks to 8.5 years with occipito-frontal circumference < 2nd percentile for age; 83 age-equivalent normocephalic controls.Outcome measuresAge, sex, weight, height, body mass index, occipito-frontal circumference, and diagnosis prompting the MRI scan. Sixteen craniometric measures to determine specific ratios and age-related changes in brain shape and size.ResultsMicrocephalic infants and children not only have abnormally small brains but also proportionately lower weights and heights. The brain volumes of both primary and secondary microcephalics were quite variable, ranging from 266 to 723 cm3 and 440 to 730 cm3, respectively (p = 0.34). Despite their smaller sizes, the shapes of 15/21 (71%) microcephalic brains were similar to those of age-equivalent controls. Cerebral hemispheric configurations were not consistent among the 6 misshapen brains, which included 2 primary, 3 secondary, and 1 unknown microcephalics. Older microcephalic brains could be distinguished from their normocephalic counterparts by two specific craniometric ratios (frontal cerebellar pole/sagittal cerebral length; axial temporal width/axial cerebellar width), each incorporating cerebral and cerebellar dimensions in either length or width.ConclusionsThe findings should provide useful information for distinguishing the characteristics of both modern and ancient microcephalic from normocephalic brains.