II. Lesions in Meninges and Ventricular System

B. Subdural Hemorrhage (cont)

Chronic subdural hemorrhage is common in infants, the elderly, alcoholics, epileptics and demented individuals. Contributing factors include frequent head trauma and an enlarged subdural space (due to cerebral atrophy), providing less support for veins traversing this space. Chronic subdural hemorrhage follows mild trauma (sometimes forgotten by the patient) and symptoms may not occur for weeks to months after the trauma due to the slow rate of blood accumulation. Symptoms include seizures, headaches, confusion, behavioral changes, and signs of increased intracranial pressure;   neurological signs may mimic those of degenerative disorders or neoplasms. Among diagnostic tests, CT scan or MRI is the most useful.  

3. Pathology. The hematoma is encapsulated by a pseudomembrane composed of granulation tissue derived from the inflammatory reaction in the dura. The membrane forms initially at the clot surface facing the dura and is called the outer membrane. It extends around the clot to the surface facing the arachnoid, to form the thinner inner membrane. Subsequent episodes of rebleeding may occur, expanding the mass, followed by reorganization with a decrease in size.  (Waxing and waning of neurological signs may correspond to the changes in hematoma size).