Abstract
IntroductionIt is generally assumed that intracranial volume (ICV) remains constant after peaking in early adulthood. Thus ICV is used as a ‘proxy’ for original brain size when trying to estimate brain atrophy in older people in neuroimaging studies. However, physiological changes in the skull, such as thickening of the frontal inner table, are relatively common in older age and will reduce ICV. The potential influence that inner table skull thickening may have on ICV measurement in old age has yet to be investigated. MethodsWe selected 60 (31 males, 29 females) representative older adults aged 71.1–74.3years from a community-dwelling ageing cohort, the Lothian Birth Cohort 1936. A semi-automatically derived current ICV measurement obtained from high resolution T1-weighted volume scans was compared to the estimated original ICV by excluding inner skull table thickening using expert manual image processing. ResultsInner table skull thickening reduced ICV from an estimated original 1480.0ml to a current 1409.1ml, a median decrease of 7.3% (Z=−6.334; p<0.001), and this reduction was more prominent in women than men (median decrease 114.6 vs. 101.9ml respectively). This led to potential significant underestimations of brain atrophy in this sample by 5.3% (p<0.001) and obscured potential gender differences. ConclusionsThe effects of skull thickening are important to consider when conducting research in ageing, as they can obscure gender differences and result in underestimation of brain atrophy. Research into reliable methods of determining the estimated original ICV is required for research into brain ageing.
Highlights
It is generally assumed that intracranial volume (ICV) remains constant after peaking in early adulthood
We investigated the potential influence of inner table skull thickening on measurement of ICV and estimates of brain atrophy in a cohort of community-dwelling older adults
The absolute difference between current and estimated original ICV was greater for women 114.6 ml (z = − 4.541; p b 0.001) than for men 101.9 ml (z = − 4.457; p b 0.001), confirming that women showed a greater decrease in ICV due to inner table skull thickening (8.3%) than did men (6.2%)
Summary
It is generally assumed that intracranial volume (ICV) remains constant after peaking in early adulthood. Results: Inner table skull thickening reduced ICV from an estimated original 1480.0 ml to a current 1409.1 ml, a median decrease of 7.3% (Z=−6.334; p b 0.001), and this reduction was more prominent in women than men (median decrease 114.6 vs 101.9 ml respectively) This led to potential significant underestimations of brain atrophy in this sample by 5.3% (pb 0.001) and obscured potential gender differences. Physiological changes of the skull such as hyperostosis frontalis interna (HFI), thickening of the inner table of the frontal region of the skull, have long been documented in the medical literature [4] Whereas it is commonly observed by radiologists in older adults, skull thickening is not often mentioned in ageing research, possibly due to the benign nature of the changes [5].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
