Because acute subdural hematoma (SDH) is not only the most common type of intracranial mass lesion, occurring in about one third of those with severe head injuries (Glasgow Coma Scale [GCS] score <9), but also associated with high mortality and morbidity rates, the emergent management of acute SDH is critical. See the Glasgow Coma Scale calculator.
Traumatic acute subdural hematoma has a high mortality despite intensive treatment. In a study of patients with traumatic acute subdural hematoma, a midline shift exceeding the thickness of the hematoma by 3 mm or more at the initial CT predicted mortality in all cases. Of 59 patients, 29 died, with median survival being 2 days (0–276). Of the nonsurviving patients, 21 (70%) had an initial GCS score of 5 or less.
An acute subdural hematoma is a rapidly clotting blood collection below the inner layer of the dura but external to the brain and arachnoid membrane (see the first image below). Two further stages, subacute and chronic, may develop with untreated acute SDH. Generally, the subacute phase begins 3-7 days after acute injury (surgical literature favors 3 days; radiologic literature favors 7days) (see the second image below). The chronic phase begins about 2-3 weeks after acute injury.
Acute subdural hematoma. Note the bright (white) image properties of the blood on this noncontrast cranial computed tomography (CT) scan. Note also the midline shift. Image courtesy of J. Stephen Huff, MD.
Subacute subdural hematoma. The crescent-shaped clot is less white than on the computed tomography (CT) scan of the acute subdural hematoma in the previous image. Despite the large clot volume, this patient was awake and ambulatory. Image courtesy of J. Stephen Huff, MD.
Delayed acute subdural hematoma is defined as an acute SDH that is not apparent on the initial CT scan but appears on a follow-up CT scan. Delayed acute SDH occurs. in about 0.5% of acute SDH patients treated with surgery.
Delayed acute SDH occurs mainly in middle-aged and elderly persons who are either on anticoagulation or antiplatelet therapy. Neurologic deterioration occurs within the first 24 hours for 70% of the patients.