Epidural and Subdural Hematomas

Extra-axial; between dura and skull (often temporal bone), or dura and vertebrae if spinal.

Most commonly traumatic; frequently involves skull fracture. Typically an arterial bleed (middle meningeal artery), but can also be venous.

More commonly seen in younger patients; attributed to traumatic nature as well as increased adherence of dura to skull in older individuals.

Lucid interval common.
Ipsilateral blown pupil → due to increased ICP and resulting uncal herniation/CN3 compression.
+/– vasopressor response (widened pulse pressure and decreased HR response to increased intracranial pressure)
- Widened pulse pressure (increased systolic, decreased diastolic)
- Bradycardia
- Irregular respirations

Usually does not cross suture lines.

Often see associated bony abnormality due to fracture.

Characteristic lentiform (biconcave) shape.
- If continued bleeding during CT, may see swirl sign.
- +/– midline shift and compression of ventricles.

MRI

May see displaced dura as a hypo-intense line on T1 and T2 sequences.

Neurosurgical Intervention

Between dura and arachnoid mater [potential space].

Rupture of bridging veins between the brain and major venous sinuses.

- Brain demonstrates some degree of movement within skull, while bridging veins are fixed → creates shearing forces that can tear veins.

Infants: Non-accidental injury (child abuse)
Young adults: Trauma (especially MVCs); vascular compromise (AVMs, infection, autoimmune disease, connective tissue disorders)
Elderly/frail: Falls

Can be acute or chronic:

- Acute: Most patients present with some degree of altered consciousness or mentation. Can see focal neurologic deficits, especially pupillary abnormalities and slurred speech. Headache, nausea, and vomiting also very common.
- Chronic: Major cause of (potentially reversible) pseudodementia in the elderly.

Findings depend on age of bleed (hyperacute, acute, subacute, or chronic).

Hyperacute

(<1 hour) Less-common scenario than acute/chronic.
May note swirl sign on CT, representing a mixture of clot, serum and unclotted active bleeding.

Acute

Classically seen as a hyperintense, crescent-shaped extra-axial collection.
May rarely appear isodense in the setting of clotting disorders, anticoagulation, or severe anemia.

Subacute

May be difficult to appreciate, due to tendency of aging clot toward isodensity with surrounding tissue.
May see effacement of sulci or midline shift.
Sulci may appear to “fade” into the subdural at the edges.

Chronic ( > 3 weeks old)

Neomembrane formation: Composed of two layers (inner/outer), which secrete enzymes preventing clot formation. Seen exclusively in chronic SDH.
- Chronic subdural content is more liquid in consistency than that of a subacute bleed.
The SDH becomes more hypodense on imaging over time, making the chronic bleed easier to appreciate than an isodensesubacute bleed.
If bilateral, may not have significant midline shift.