Subdural Hematoma

Contributed by: Yousuf Qaseem, University of New Mexico School of Medicine, 1 University of New Mexico, Albuquerque, NM 87131
Overview
  • Subdural hematomas are a subtype of intracranial hemorrhage that represent bleeding between the dura and the arachnoid membrane. Both acute and chronic forms exist, with distinct etiologies and clinical presentations. Management and prognosis depends upon the acuity and severity of the hemorrhage.
Etiology
  • Subdural hematomas occur due to rupture of the cerebral bridging veins that drain the brain parenchyma and cross the subdural space.
  • In acute ruptures, the bridging veins are usually torn by an identifiable head injury or by high shear forces, such as whiplash, yielding an acute accumulation of blood. In contrast, subacute and chronic epidural hematomas evolve over days to weeks. These are often secondary to minor head injuries, most often in the elderly, whose bridging veins are more prone to rupture with minor trauma. Chronic subdural hematomas may also be bilateral.
Imaging
  • As with other types of intracranial hemorrhage, a non-contrast CT of the head is necessary for evaluation. Because the subdural space is not restricted by the skull suture lines, subdural hematomas appear crescent-shaped on CT, with the blood collection able to cross suture lines. This is an important distinction from epidural hematomas. Depending on the severity of the hematoma, evidence of mass effect (such as midline shift) may be present.
  • Acute subdural hematomas may appear bright white on a non-contrast CT due to the presence of new blood. However, chronic subdural hematomas may appear darker than, or even isodense with, the brain parenchyma, often making them more difficult to identify.
Clinical Features and Consequences
  • Acute subdural hematomas typically present with a fairly rapid progression of symptoms. Unlike patients with epidural hematomas, patients with acute subdural hematomas are typically obtunded from the moment of injury (though a lucid interval may occur in a minority of cases). As with epidural hematomas, severe elevation of intracranial pressure (ICP) may lead to a Cushing reflex and, if uncal or tonsillar herniation develops, stupor, coma and death (see “Epidural Hematoma”, section on Clinical Features and Consequences).
  • Chronic subdural hematomas have a much more insidious onset and heterogeneous presentation. Patients may present with progressively worsening drowsiness, confusion, and headache. They may also exhibit personality changes, depression or neurocognitive dysfunction. Focal neurological deficits (such as hemiparesis) may be present, depending upon the location of the hematoma. If the hematoma is bilateral, localization of the neurological deficits may be difficult.

Further Reading
  • Naidech AM. 2011. "Intracranial Hemorrhage." American Journal of Respiratory and Critical Care Medicine 184.9 (2011): 998-1006


To cite this article
  • Qaseem, Y, “Epidural Hematoma” in Pathway Medicine: An Introduction to Clinical Medicine", PathwayMedicine.org (2017).