Location of the chronic subdural haematoma: role of the gravity and cranial morphology.

Chronic subdural haematoma (SDH) frequently originates from subdural hygroma (SDG). The cranial morphology can determine the location of SDG. Since SDG is the precursor of chronic SDH, the shapes of the cranium wall act an important role in location of chronic SDH. The authors tried to test this hypothesis. The computed tomographic scans or magnetic resonance images of 118 consecutive patients with chronic SDH were re-evaluated, and the symmetry of the cranium and location of the lesion were checked. The cranium was symmetrical in 55 patients (47%) and asymmetrical in 63 patients (53%). Chronic SDH was bilateral in 25 patients (21%) and unilateral in 93 patients (79%). It was more commonly bilateral in symmetrical craniums than in asymmetrical craniums (29.1% vs. 14.3%) (p = 0.0496). In 63 patients with asymmetric cranium, the chronic SDH was bilateral in nine patients, located on the opposite side of the flat side in 38 patients, and located on the same side of the flat side in 17 patients. This unequal distribution was statistically significant (p = 0.03). In four patients, the haematoma originated from the acute SDH located on the same side of the flat side. No reason could be found in the remaining 13 patients. Chronic SDH originating from SDG usually locates on the opposite to the flat side of the skull. The shape and posture of the cranium can predict the location of chronic SDH, as in the SDG.