Focal Idiopathic Calvarial Thinning: A Condition of Uncertain Prevalence and Significance.

Focal thinning of the calvarial bones unrelated to an underlying systemic disease is uncommon. Of such cases documented in the medical literature, most are bilateral parietal bone thinning, which tends to affect elderly females and results in bilateral symmetric, regularly shaped depressions of the skull. The authors describe 2 cases of unilateral, focal, irregularly shaped calvarial thinning in adolescent males that occurred without an obvious precipitating incident and were unrelated to systemic disease, a known syndrome or previous trauma. The nature and physical parameters of the deformities are demonstrated here and specific historic features such as age of onset and mode of obstetric delivery are explored. The clinical significance and potential pathogenesis of this finding is unclear, though these cases are relevant in highlighting a novel presentation that we henceforth term focal idiopathic calvarial thinning.