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

Chronic subdural haematoma (SDH) frequently originates from subdural hygrom a (SDG). The cranial morphology can determine the location of SDG. Since SD G is the precursor of chronic SDH, the shapes of the cranium wall act an im portant role in location of chronic SDH. The authors tried to test this hyp othesis. 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 sym metrical in 55 patients (47%) and asymmetrical in 63 patients (53%). Chroni c SDH was bilateral in 25 patients (21%) and unilateral in 93 patients (79% ). It was more commonly bilateral in symmetrical craniums than in asymmetri cal 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 op posite side of the flat side in 38 patients, and located on the same side o f the flat side in 17 patients. This unequal distribution was statistically significant ( p = 0.03). In four patients, the haematoma originated from t he 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 usuall y locates on the opposite to the flat side of the skull. The shape and post ure of the cranium can predict the location of chronic SDH, as in the SDG.