• Clinical science

Subdural hematoma (Subdural hemorrhage)

Abstract

Subdural hematoma (SDH) refers to bleeding between the dura mater and arachnoid membrane. It is caused by head trauma that results in a tear in the bridging vein, which connects the superficial cerebral veins to the dural venous sinuses. The onset of symptoms may be acute, subacute, or chronic. Symptoms of SDH include headaches, changes in mental status, and focal neurologic deficits. CT and MRI scans are used to diagnose SDH, which presents as a crescent-shaped collection of blood that crosses the suture lines but not the falx or tentorium. Treatment may be surgical (e.g., trephination) or supportive, depending on the size of the subdural hematoma. Supportive therapy involves close clinical monitoring, normalizing coagulation parameters of patients on anticoagulant therapy, and preventing intracranial hypertension The prognosis of patients with chronic SDH is significantly better than those with acute SDH.

Epidemiology

Sex: > (3:1)

References:[1]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

Rupture of the bridging veins caused by:

SDH may occur after trivial trauma in patients with multiple risk factors!
References:[1]

Classification

Classification is based on the onset of symptoms after the inciting event.

  • Acute SDH: immediately after trauma or rapidly within 72 hours
  • Subacute SDH; : 4–21 days after trauma
  • Chronic SDH: > 21 days after trauma

References:[1]

Pathophysiology

  • SDH is a form of intracranial hemorrhage in which blood accumulates between the dura mater and arachnoid membrane.
  • Tearing in bridging veins low-pressure venous bleeding.

References:[1]

Clinical features

Symptoms and their onset depend on the size, location, and rate of growth of the SDH.

  • Headache
  • Impaired consciousness and confusion
  • Focal neurologic signs (i.e., hemiparesis , gait, speech, or visual impairment, personality changes, or a dilated or nonreactive pupil )
  • Memory impairment

Both SDH and epidural hematoma can occur after head trauma and cannot be differentiated based on symptoms alone!
References:[1]

Diagnostics

  • SDH is diagnosed on brain imaging.
    • Non-contrast head CT scan is the modality of choice.
    • MRI is indicated when CT scan is inconclusive but suspicion for subdural hematoma is high.
  • Appearance on brain imaging
    • Crescent-shaped, concave hemorrhage that crosses suture lines but not the midline
    • Varies depending on clot age and organization:
CT MRI
Acute SDH Hyperdense with respect to the cortex Hypointense to isointense with respect to grey matter
Subacute SDH Isodense with respect to the cortex after 10–14 days Mostly hyperintense
Chronic SDH Hypodense with respect to the cortex and may appear isodense with respect to cerebrospinal fluid Mostly isointense with respect to cerebrospinal fluid

In contrast to SDH, epidural hematoma is lentiform on imaging and does not cross suture lines but can cross the falx or tentorium!

References:[2][3]

Treatment

Treatment depends on size and onset of SDH, as well as the patient's condition.

  • General measures
    • Close clinical monitoring (especially neurological status)
    • Measuring and optimizing intracranial pressure; see ICP management
    • Normalizing of clotting parameters
      • Different substances are available: e.g., fresh frozen plasma, vitamin K, recombinant factor VIIa
      • Critical trade-off: risk of thromboembolic event as a result of the underlying disease
  • Conservative treatment
    • Indicated if no clinical signs of herniation are present and the neurological status is stable, midline shift < 5 mm, and the hematoma is < 10 mm
    • Monitoring with serial CT scans
  • Surgical decompression
    • Indications (Only one of the following criteria must be met.)
      • Clinical signs of herniation
      • Unstable neurologic status
      • Midline shift > 5 mm
      • Hematoma > 10 mm
    • Procedures
      • Trephination and drainage of hematoma: A burr hole is drilled in the skull and the hematoma is drained.
      • Craniotomy and evacuation of hematoma: A bone flap is removed from the skull and the hematoma is evacuated.

References:[4]

Prognosis

  • The prognosis of chronic SDH is better than that of acute SDH.

References:[5][6]