Acute subdural hematoma requiring surgery in the subacute or chronic stage.

The aim of this study was to clarify the clinical characteristics and pathophysiology of conservatively treated cases of acute subdural hematoma (ASDH) that ultimately require surgery in the subacute or chronic stage, and devise an appropriate form of management for them. A total of 50 patients with ASDH were admitted to our institution during a 5-year period. Hematoma removal in the subacute or chronic stage was performed in 8 patients. The ASDH had been caused by a fall in 5 patients. Five patients had been treated with antiplatelet agents. Fluid-attenuated inversion recovery magnetic resonance (MR) imaging demonstrated an irregularly shaped hematoma with gyrus patterns in 4 of 5 patients. Diffusion-weighted MR imaging demonstrated a two-layered hematoma structure in 3 of 4 patients. The hematoma was removed via a craniotomy, a small craniotomy, and a burr hole in 1, 1, and 6 patients, respectively. At surgery in the craniotomy case, a solid clot was located beneath the dura, and a liquid hematoma was located close to the brain. After hematoma removal, no inner membrane was observed on the brain surface. One patient had typical chronic subdural hematoma in the subacute stage, and 2 patients had so-called subacute subdural hematoma (SASDH) in the chronic stage. Although the majority of such cases can be treated by burr-hole surgery, a small craniotomy or craniotomy ought to be considered as a further surgical option if SASDH is diagnosed on the basis of clinical and radiological data, especially diffusion-weighted MR imaging.