Clinical Aspects of Subdural Hemorrhage (SDH)

Acute Subdural Hematoma

Epidemiology

Acute subdural hematoma (ASDH) is an intracranial space-occupying lesion that often occurs because of the tearing of bridging or cortical surface veins, secondary to a physical head trauma. ASDHs are often accompanied by cortical contusions, parenchymal hematomas, or global shearing injury such as diffuse axonal injury (DAI). Approximately 10–20% of all patients admitted with a traumatic brain injury (TBI) have an ASDH. The incidence increases to 60% for patients with a Glasgow Coma Scale (GCS) score of 8 or less. Approximately 70% of such patients are older than 45 years and 40% are older than 65 years, with a male:female ratio of 3:1. As life expectancy rises, the incidence of ASDH is also expected to rise. The Traumatic Coma Data Bank reports that most ASDHs are caused by motor vehicle accidents (MVAs) and falls. MVAs are more frequent in the younger population (15–30 years) and falls are more frequent in the age group of 45–80 years .

Physiologic Changes Associated With ASDH

Patients with an ASDH often have markedly decreased cerebral blood flow (CBF) immediately after injury, despite having normal blood pressure and arterial oxygenation. CBF is thought to decrease because of an increase in intracranial pressure (ICP) and a subsequent decrease in cerebral perfusion pressure (CPP). Other local phenomena such as dysautoregulation, cerebral vasospasm, and reduced metabolic demand contribute to decreased CBF and the associated morbidity .

Clinical Findings

Symptoms of ASDH can vary depending on the size and associated cerebral injuries. Small ASDHs can present with headache and meningismus. Larger ASDHs often present with altered consciousness, pupillary asymmetry, or hemiparesis. A dilated pupil can be seen on the ipsilateral side of the hematoma as the lesion causes indirect compression of the oculomotor nerve [cranial nerve (CN) III]. Motor findings are usually contralateral but can also be ipsilateral because of the Kernohan notch phenomena. If the hematoma is compressing the ipsilateral cerebral peduncle, motor weakness is typically contralateral. However, if the hematoma compresses the contralateral cerebral peduncle against the tentorium, weakness is on the ipsilateral side. This can be seen radiographically as an indentation in the contralateral cerebral crus by the tentorium. Careful attention should be paid to the elderly patients on anticoagulants, as even a mild head trauma can cause severe delayed ASDHs. Thus, some have suggested that this patient population should be admitted for close monitoring.

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