Widening of the diploic space refers to expansion of the spongy or cancellous bone between the inner and outer tables of the calvarium. The diploic space is the medullary cavity of the skull, and a location of normal physiologic hematopoiesis in adults. Thus, expansion of this structure most commonly occurs in the setting of chronically increased intramedullary hematopoiesis. The widened appearance is most commonly bilateral.
Most commonly caused by systemic pathologies such as:
- chronic hemolytic disorders: may be associated with vertical striations running in diploic space giving rise to the characteristic hair on end sign
- metabolic disorders
- 1. Lloret I et al, Calvarial Lesions: A Radiological Approach to Diagnosis, Acta Radiologica 2009, 50:5, 531-542
- 2. Hollar M, The Hair-on-End Sign, Radiology Signs in Imaging, November 2001 Volume 221, Issue 2