Ring-enhancing collection with restricted diffusion on MRI
Neurosurgical emergency requiring drainage
Important mimics
Structural mimics
Subdural hygroma
CSF-density collection (hypodense), often post-traumatic
Does not represent blood; may develop weeks after injury
Cerebral contusion
Intraparenchymal heterogeneous lesion
Associated with coup-contrecoup injury pattern
Subdural metastases or lymphoma
Progressive headache without trauma; hyperdense on CT but hyperintense on T2 MRI
History of malignancy and lack of trauma are key clues
Clinical mimics
Spontaneous intracranial hypotension
Bilateral SDH in younger patients with positional headache
Orthostatic headache worsening on standing
CSF leak as underlying cause
Dementia
Chronic SDH can mimic or exacerbate cognitive decline
ICD-10 F03 versus G31.9
CT head required for new or accelerated decline
Transient ischemic attack or stroke
Focal deficits; CT early may be negative for ischemia
Laboratory Tests
Core labs
Hematologic workup
Complete blood count with platelets
Thrombocytopenia increases bleeding risk and affects reversal strategy
Leukocytosis may suggest concurrent infection
Coagulation panel
PT and INR: warfarin reversal target INR 1.4 or less for neurosurgery
aPTT: heparin or factor deficiency assessment
Type and screen
Required if surgical intervention anticipated
Crossmatch if intraoperative transfusion likely
Metabolic panel
Electrolytes and renal function
Sodium: hyponatremia exacerbates cerebral edema
Renal function: critical for DOAC clearance assessment and mannitol monitoring
Hepatic function panel
Coagulopathy from liver disease
Hepatic encephalopathy in differential
Anticoagulation-specific labs
DOAC-specific testing
Anti-Xa level for factor Xa inhibitors (apixaban, rivaroxaban)
Order when timing of last dose is uncertain
Guides reversal strategy
Thrombin time or anti-Xa calibrated for dabigatran
Normal thrombin time excludes clinically relevant dabigatran activity
Dilute thrombin time (Hemoclot) or ecarin clotting time if available
Most accurate for dabigatran quantification
Viscoelastic testing
Thromboelastography or ROTEM when available
Guides targeted blood product and reversal agent selection
Especially useful in polytrauma with multifactorial coagulopathy
Additional tests
Toxicology and metabolic workup
Blood alcohol level
Alter mental status workup and fall etiology
Chronic alcohol use associated with brain atrophy and coagulopathy
Urine drug screen
Anticoagulants or medications contributing to fall
Glucose
Hypoglycemia may cause or mimic altered mental status
Lactate
If concern for shock or polytrauma
Lactate 2 mmol/l or greater suggests hypoperfusion
Diagnostic Tests
Scoring Systems
Head CT decision rules
Canadian CT Head Rule
High-risk features: GCS score 15 at 2 hours post-injury, suspected open or depressed skull fracture, signs of basilar skull fracture, vomiting 2 or more episodes, age 65 or older
Medium-risk features: amnesia before impact 30 minutes or more, dangerous mechanism
High sensitivity for clinically important TBI
New Orleans Criteria
Seven variables: headache, vomiting, age over 60, drug or alcohol intoxication, short-term memory deficit, seizure, clinical evidence of trauma above clavicles
Any variable positive warrants CT
Applies to GCS 15 patients only
SDH severity classification
Markwalder Grading Scale for chronic SDH
Grade 0: neurologically normal
Grade 1: alert and oriented, mild symptoms
Grade 2: drowsy or disoriented, mild focal deficits
Grade 3: stuporous, severe focal deficits
Grade 4: comatose, decerebrate or decorticate posturing
GCS thresholds
GCS less than 9: coma; ICP monitoring and surgical consideration
GCS 13 to 15: mild TBI; may observe with serial exams if small SDH
Modified Rankin Scale
Functional outcome assessment pre and post intervention
0: no symptoms
5: severe disability
Used in chronic SDH trial endpoints including Dex-CSDH and Dutch cSDH trials
MRI
MRI brain indications
Subacute SDH detection
Isodense to brain on CT between days 7 to 21; MRI superior for detection
T1 hyperintensity (methemoglobin) and T2 signal changes distinguish age of blood
Underlying pathology evaluation
Dural metastases or tumor as cause of spontaneous SDH
Cerebral amyloid angiopathy imaging features on gradient echo
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