Subdural hemorrhage (summary)

Subdural haemorrhage (SDH) is a collection of blood between the dura and the arachnoid layers of the meninges. They are common and can occur in any age range, usually related to a history of head trauma. Prognosis tends to depend on the extent of the bleed and associated mass effect.

Clinical featuresReference article

Subdural haemorrhages can occur across many agesThis is a summary article for subdural haemorrhage. However, but with different mechanisms at different ageswe do have a more in-depth reference article:subdural haemorrhage.

Summary

• epidemiology
  • children: non-accidental injury ¹
  • adults: high energy trauma, e.g. road traffic collisions
  • elderly: falls (there may not be a clear history of trauma)

  Presentation

  Acute subdurals are

• presentation
  • acute
    • usually associated with head injury, particularly in younger patients who may have evidence of head injury, e.g. extradural haemorrhage, cerebral contusions. There
      • may be associated contusions or extradural haemorrhage
    • underlying abnormalities such as arteriovenousvascular malformations in spontaneous bleeds.

      Subacute

  • subacute or chronic subdural haemorrhages can present in the elderly as
    • confusion or withand vague neurological change. SDH is
    • a classic cause of pseudo-dementia and there may only be a history of minor head injury (sometimes there is no history of head trauma) ². Special attention should be given topseudodementia
    • beware patients on oral anticoagulants such asanticoagulants, e.g. warfarin.

      See

• pathophysiology
  • tearing of bridging veins found in the article: EDH v SDH

    Treatment

    Subdural haemorrhages usually merit

    subdural space
  • veins are subject to shearing forces
    • occurs with lower forces in the elderly
• investigation
  • non-contrast CT head
• treatment
  • correction of abnormal coagulation
  • discussion with neurosurgical services. The treatment can depend on the neurological impact ⁵ of the mass effect and size of the bleed.

    Small chronic SDHs may be incidental findings and

  • small subdurals can be observed with repeated scans.

    Correction of abnormal coagulation can be performed prior to neurosurgical intervention with haematologist advice. Evacuation

    CT
  • surgical evacuation of the bleed is usually required in symptomatic cases but canclot
    • may carry high morbiditysignificant mortality and mortality ^4,5. Acute SDHs may need urgent craniotomy to control the clot. Symptomatic subacute or chronic clots can be managed with burr-hole drainage as the older clots can be more easily removed from smaller spaces.morbidity

Pathophysiology

The bleed in subdural haemorrhages usually comes from tearingRole of "bridging veins" found in the subdural space ³. These veins can be subject to shearing or tearing when the head is subject to a change in velocity (as in head injury). Tearingimaging

• initial diagnosis
• assessment of these veins may occur with less force in the elderly where theassociated mass effect of cerebral atrophy can leave these stretched veins more vulnerable to damage ².

  CSF may leak into the subdural space if the

• look for an underlying arachnoid mater is damaged. A small proportion of subdurals can rebleed as veins are stretched and subsequently damaged.cause
• suggest further imaging
• follow up

Radiographic features

Subdural haemorrhages are typically unilateral (85%) ⁴ and follow a crescent-like distribution around the periphery of the brain. They are not limited by sutures and can fill dural reflections (falx cerebri, tentorium).

CT

Non-contrast CT is usually enough to make the diagnosis but contrast can be used in challenging cases, particularly with the different appearances of these bleeds over time.

Acute

Acute subdural haemorrhages are hyperdense collections. While many are uniformly hyperdense, up to half can have mixed appearances as (hypodense) unclotted blood, serum or CSF is involved in the collection.

Acute bleeds may be isodense and therefore difficult to identify in patients with anaemia or coagulopathies (including warfarinisation) where it fails to clot. The clotting process causes increased density and failure to clot therefore results in an isodense collection.

Subacute

In the first few weeks after a bleed, the clot and proteins are broken down making the collection appear hypo or isodense. Here, indirect signs of a subdural collection are important to identify, e.g. a gap between the cerebral sulci and skull, mass effect or an apparent ill-defined, thickened cortex.

Isodense subdural collections can be difficult to see if there are identical density to adjacent brain parenchyma. Contrast enhanced CT is often useful in this instance if MRI is unavailable.

Be aware of the acute isodense SDH in anaemic patients.

Chronic

Over time, these collections can resolve and leave few products behind with a hypodense region on CT with density similar to CSF ².

MRI

MRI is used to assess the underlying parenchyma. The signal of blood in the subdural haemorrhage change with time and MRI can be used to age a collection.