What is the prognosis for an acute or chronic subdural hematoma, taking into account age, Glasgow Coma Scale score, hematoma size, midline shift, and anticoagulant use?

Subdural Hematoma Prognosis

The prognosis of subdural hematoma is primarily determined by age, initial Glasgow Coma Scale score, and the extent of underlying brain injury rather than the hematoma itself, with mortality ranging from 17-66% depending on these factors. 1, 2

Key Prognostic Factors

Age

• Patients ≥65 years have significantly higher mortality rates compared to younger patients, with age being one of the strongest independent predictors of poor outcome 1, 3, 2
• Older age correlates positively with mortality (p=0.007 to p=0.022 across studies) 3, 2

Glasgow Coma Scale Score

• GCS score on presentation is the most critical clinical predictor of outcome 1, 3, 2
• GCS 3-4 or GCS ≤6 on arrival carries extremely poor prognosis with mortality rates approaching 66-83% 1, 2
• GCS 13-15 (mild TBI) has excellent prognosis with 93% functional recovery when managed appropriately 4
• GCS 11-15 with minimally symptomatic presentation allows for conservative management with 93% functional recovery 4
• Patients with GCS 3-8 and bilateral pupillary dilation should not undergo surgery due to very high mortality rates 3

Pupillary Abnormalities

• Pupillary abnormalities (anisocoria or bilateral mydriasis) are strong negative prognostic indicators 3, 5
• Bilateral fixed and dilated pupils in comatose patients (GCS 3-8) predict near-universal mortality regardless of intervention 3

Hematoma Size and Midline Shift

• Midline shift ≥10 mm is significantly associated with mortality (p=0.011 to p=0.014) 3, 2
• Hematoma thickness ≥15 mm correlates with increased mortality (p=0.039) 2
• When midline shift exceeds hematoma thickness, this indicates severe underlying brain injury and worsens prognosis 3
• Smaller hematomas (<1 cm) in minimally symptomatic patients have excellent outcomes with conservative management 4

Intracranial Pressure

• Postoperative ICP >40-45 mmHg is strongly associated with poor outcome (p<0.05) 1, 3
• The ability to control ICP postoperatively is more critical to outcome than timing of surgery 1

Anticoagulant Use

• Anticoagulated patients have 0.6-1.4% risk of delayed intracranial hemorrhage even after negative initial CT 6
• Among anticoagulated patients with delayed hemorrhage, mortality occurs in approximately 0.6% of cases 6
• Patients on warfarin or clopidogrel with negative initial CT rarely require neurosurgical intervention for delayed hemorrhage 6

Prognostic Models

IMPACT and CRASH Models

• The CRASH CT model demonstrates the highest discriminatory performance for predicting mortality (AUC 0.88-0.91) and unfavorable outcome (AUC 0.84-0.88) 6
• The CRASH CT model incorporates: age, GCS total score, pupillary reactivity, major extracranial injury, petechial hemorrhages, obliteration of third ventricle or basal cisterns, traumatic subarachnoid hemorrhage, midline shift >5mm, and non-evacuated hematoma 6
• The IMPACT Lab model also shows strong performance (AUC 0.81-0.85 for mortality) and includes: age, GCS motor score, pupillary response, hypoxia, hypotension, Marshall CT classification, traumatic subarachnoid hemorrhage, epidural hematoma, glucose, and hemoglobin 6

Acute vs. Chronic Subdural Hematoma Prognosis

Acute Subdural Hematoma

• Overall mortality for severe acute subdural hematoma (GCS 3-7) is approximately 66% with only 19% achieving functional recovery 1
• The extent of primary underlying brain injury is more important than the subdural clot itself in determining outcome 1
• Motorcycle accidents as mechanism of injury carry worse prognosis 1

Minimally Symptomatic Acute Subdural Hematoma

• Patients with GCS 11-15 and small hematomas managed conservatively have 93% functional recovery 4
• Only 6% of conservatively managed patients develop chronic subdural hematoma requiring delayed surgery 4

Chronic Subdural Hematoma

• Chronic subdural hematoma generally carries better prognosis than acute, though specific mortality data varies by patient age and comorbidities 7
• Burr hole drainage is the preferred approach with lower morbidity than craniotomy 8

Factors NOT Significantly Associated with Prognosis

• Timing of surgery (even at hourly intervals) does not significantly affect mortality or morbidity in acute subdural hematoma, contrary to older beliefs 1
• Laterality of hematoma does not predict outcome 5
• Sex and race do not correlate with outcome 5
• Presence of subarachnoid hemorrhage, epidural hemorrhage, or contusions alone do not independently predict mortality 2

Special Populations

Aneurysmal Subdural Hematoma

• Only 20% have good outcome at discharge, improving to 40% at 6-12 months 5
• Younger age, smaller aneurysm size, and lower Hunt-Hess score predict better outcome 5
• Clinical presentation is more important than radiographic findings (hematoma size, midline shift) for prognosis 5

Elderly Patients on Anticoagulation

• 70% of elderly anticoagulated patients who develop delayed subdural hematoma deteriorate within the first 24 hours 7
• Delayed hemorrhage occurs in 1.4-4.5% of anticoagulated patients even with initially negative CT 7

Critical Prognostic Thresholds

For surgical decision-making based on prognosis:

• GCS 13-15: Excellent prognosis with conservative management (93% functional recovery) 4
• GCS 9-12: Variable prognosis, surgical decision based on imaging and clinical trajectory 3
• GCS 3-8 with reactive pupils and midline shift <10mm: Surgery indicated, guarded prognosis 3
• GCS 3-8 with bilateral fixed pupils: Extremely poor prognosis, surgery not recommended 3
• Midline shift >10mm with shift exceeding hematoma thickness and ICP >40mmHg: Very poor prognosis, surgery may not be beneficial 3