What symptoms characterize acute, sub‑acute, and chronic subdural hematoma and when should neuroimaging be performed?

Subdural Hematoma Symptoms and Neuroimaging Indications

Acute Subdural Hematoma (within 72 hours)

Acute subdural hematoma presents with rapid neurological deterioration, typically within hours of injury, and requires immediate CT imaging in any patient with altered mental status, focal neurological deficits, or Glasgow Coma Scale (GCS) ≤13 following head trauma. 1

Clinical Presentation

• Impaired consciousness or decreased level of consciousness progressing over minutes to hours 1
• Focal neurological deficits referable to the hematoma location 1
• Severe headache with acute onset 1
• Vomiting (associated with increased intracranial pressure) 1
• Seizures may occur at presentation 1
• Systolic blood pressure >220 mmHg suggests intracranial hemorrhage 1
• Coma or rapidly declining GCS indicates severe injury requiring immediate intervention 2

When to Perform Neuroimaging

• Immediate non-contrast CT head is mandatory for any patient with suspected acute subdural hematoma, as clinical characteristics alone cannot distinguish hemorrhage from ischemia 1
• CT should be performed within 1 week of symptom onset to reliably demonstrate high-density acute blood 1
• Any patient with altered mental status (GCS ≤13) requires immediate CT before any other intervention, including neurosurgical consultation 2
• Patients with abnormal neurological examination have significantly higher rates of positive CT findings requiring intervention 1

Subacute Subdural Hematoma (3 days to 3 weeks)

Subacute subdural hematoma is particularly dangerous because it causes acute neurological worsening within hours during the second week post-injury, distinguishing it from the more gradual deterioration of chronic hematoma. 3

Clinical Presentation

• Rapid neurological deterioration typically occurring during the second week after injury 3
• Progressive decline in GCS over hours rather than days 3
• Headache and dizziness that may worsen acutely 4
• Focal neurological deficits that develop or worsen suddenly 5
• Isolated cranial nerve palsies (e.g., oculomotor nerve palsy) may be the only presenting sign in tentorial locations 6
• Average disease duration before admission is 36.6 hours 3

When to Perform Neuroimaging

• CT head should be performed immediately when patients present with worsening symptoms in the 3-21 day window post-injury 3
• Iso-density hematoma on CT in a young person is a predictive factor for rapid neurological aggravation and requires urgent surgical consideration or intensive monitoring 3
• MRI with fluid-attenuated inversion recovery (FLAIR) sequences should be performed within 2 weeks to demonstrate extracellular methemoglobin 1
• Diffusion-weighted MRI can demonstrate a two-layered hematoma structure characteristic of subacute hematoma 5

Chronic Subdural Hematoma (>3 weeks)

Chronic subdural hematoma presents with gradual, progressive neurological decline over weeks to months, often in elderly patients with cerebral atrophy, and may be managed conservatively if small without mass effect. 7, 3

Clinical Presentation

• Progressive headache developing over weeks to months 4
• Gradual cognitive decline or confusion 1
• Gait disturbances and balance problems 1
• Focal neurological deficits that develop slowly 7
• Symptoms similar to hepatic encephalopathy including drowsiness and altered consciousness, requiring careful differentiation 1
• Hemiplegia may accompany chronic subdural hematoma 1
• Average disease duration before admission is 13.1 days for chronic hematoma 3
• Cerebral atrophy is present in over half of patients with chronic subdural hematoma 7

When to Perform Neuroimaging

• CT head is appropriate for patients presenting with gradual decline after remote fall, as it reliably detects chronic subdural hematoma 1
• MRI is preferred for subacute or chronic head trauma when rapid detection of acute hemorrhage is not the primary concern, as it is more sensitive for subtle findings 1
• Neuroimaging should be performed when patients present with unexplained cognitive or neurological deficits weeks to months after injury 1
• Serial CT scanning is recommended for conscious patients with small acute subdural hematomas managed conservatively 7

Critical Pitfalls and Management Principles

Common Diagnostic Errors

• Do not rely on clinical features alone to distinguish subdural hematoma from other pathology—neuroimaging is mandatory 1
• Iso-density hematoma on CT (subacute phase) can be easily missed and requires high clinical suspicion, especially in younger patients 3
• Subdural hematoma must be differentiated from cerebral hemorrhage, edema, hyponatremia, hepatic encephalopathy, and alcohol-related neurological diseases 1
• Tentorial subdural hematomas may present only with isolated cranial nerve palsies and require careful neuroanatomical correlation 6

Airway and Hemodynamic Management

• Secure the airway immediately in any patient with altered mental status (GCS ≤13) before obtaining neurosurgical consultation 2
• Maintain systolic blood pressure >100 mmHg and mean arterial pressure 80-110 mmHg to ensure adequate cerebral perfusion 2
• Avoid hypotension and hypoxia at all costs, as these cause secondary brain injury and dramatically worsen outcomes 2

Surgical Considerations

• Hematoma thickness >10 mm is associated with higher likelihood of requiring surgical intervention 7
• Hematoma volume >53 ml significantly increases the need for operative management 7
• Rapid drainage should be avoided—slow decompression with closed-system drainage prevents devastating complications including contralateral hemorrhage and hyperperfusion injury 4
• Conscious patients with small acute subdural hematomas without mass effect may be safely managed conservatively with serial imaging 7