Epidural Hematoma

• Vascular injury mechanism: Traumatic head injury causes sudden acceleration-deceleration or direct impact forces that lacerate the middle meningeal artery (branches) in ~90% of EDH cases, or cortical vessels in remaining cases. The middle meningeal artery typically runs in grooves along the inner table of the temporal bone and is particularly vulnerable at the junction of the anterior and middle fossae. Arterial bleeding (rather than venous) creates high-pressure accumulation that strips the dura from the inner table of the skull, creating an expanding hematoma in a space with limited compliance. Unlike subdural hematoma where blood strips the dura from beneath, epidural blood accumulates between dura and bone, resulting in a characteristic lens-shaped (biconvex) appearance on neuroimaging.

• Intracranial pressure dynamics and mass effect: The accumulating blood volume within the closed cranial vault increases intracranial pressure (ICP) according to the Monro-Kellie hypothesis. The brain exists in homeostatic balance with cerebrospinal fluid and blood; additional mass lesions compress brain tissue, shift midline structures, and eventually cause transtentorial herniation. Initially, compensatory mechanisms include decreased cerebral blood volume and CSF displacement rostrally, but these have limited reserve. As hematoma expands, focal mass effect causes ipsilateral compression of the temporal lobe and uncus, leading to compression of the ipsilateral oculomotor nerve (CN III) and subsequent ipsilateral pupillary dilation. Continued expansion causes uncal herniation with midbrain compression, culminating in brainstem dysfunction, loss of protective airway reflexes, and death if untreated.

• The "talk and die" clinical trajectory: The classic presentation reflects the temporal dynamics of arterial bleeding into a compliant space. Initial head trauma may cause brief unconsciousness or remain relatively asymptomatic as ICP rises but remains within compensatory threshold. Over minutes to hours, as the hematoma expands and ICP exceeds autoregulatory capacity, patients experience rapid neurologic deterioration with decreased consciousness, lateralizing signs (ipsilateral pupillary dilation, contralateral motor deficit), and potential herniation. This contrasts with acute subdural hematoma, where venous tearing causes more immediate unconsciousness. The "lucid interval"—period of apparent improvement or consciousness between initial trauma and rapid deterioration—occurs in approximately 20-30% of EDH patients and represents the window between initial injury and critical ICP elevation.

• Relationship to age and dural adhesions: In elderly patients, the dura is more firmly adherent to the inner skull table due to loss of elasticity and increased adhesions. This anatomic difference results in epidural hematoma occurring less frequently in older patients despite equal trauma severity, but when EDH does occur in the elderly, the hematoma may expand more slowly. Pediatric patients have more pliable dura with fewer adhesions, allowing rapid dissection and large hematoma volumes, but paradoxically better compensatory capacity of the pediatric cranium. This age-related variation explains why EDH is relatively more common in younger populations—the dura more easily strips from bone despite higher threshold for significant injury.

• Location-specific pathophysiology: Approximately 70% of EDH occur in the temporal region overlying the middle meningeal artery distribution. Anterior fossa EDH (5-10% of cases) typically results from frontal trauma and may involve anterior meningeal artery branches. Posterior fossa EDH (rare, 2-8% of cases) is particularly dangerous as small volumes cause significant brainstem compression and elevated mortality (up to 50%) due to limited space for mass effect. Tentorial EDH is exceptionally rare but highly morbid as it directly compresses midbrain structures.

• Head trauma severity and mechanism: The primary etiology is traumatic head injury, though the trauma may be relatively minor in some cases. Motor vehicle accidents, falls, assaults, and sports-related injuries represent the most common mechanisms. Notably, older adults may sustain EDH from falls from standing height, whereas younger patients typically require higher-energy mechanisms. In children, the threshold for significant injury is lower than adults, and apparently minor head trauma (such as falls in toddlers or playground collisions) can rarely produce symptomatic EDH.

• Coagulopathy and anticoagulation: Patients on warfarin, direct oral anticoagulants (DOACs), or antiplatelet agents have increased risk of EDH expansion and worse outcomes. Chronic liver disease, thrombocytopenia, hemophilia, or von Willebrand disease substantially increase hemorrhage volume and expansion rate. Acute administration of thrombolytics or fresh trauma during anticoagulation therapy dramatically elevates risk. This has major implications for clinical management, as anticoagulation reversal becomes urgent in EDH patients on these medications.

• Age-related factors: Children and young adults (ages 5-40 years) have the highest incidence of symptomatic EDH due to more easily strippable dura, though their greater physiologic reserve allows better outcomes with treatment. Elderly patients have lower incidence due to firm dural adhesions, but when EDH occurs, small volumes may have disproportionate mass effect due to brain atrophy creating less compressible space. Infants are at particular risk for EDH from inflicted head injury (child abuse), which must be considered in all infants with unexplained EDH.

• Underlying structural abnormalities: Cortical brain atrophy in elderly patients, hydrocephalus, or previous brain injury increases vulnerability to EDH from minor trauma by reducing compensatory space. Pachymeningitis, meningitis sequelae, or previous dural surgery may alter normal dural-bone relationships.

• Altered level of consciousness with characteristic trajectory: The classic presentation features an initial period of unconsciousness from the primary head injury, followed by a lucid interval of apparent recovery and normal mentation (present in 20-30% of cases), then rapid deterioration into unresponsiveness over minutes to hours. This trajectory reflects expanding hematoma volume exceeding compensatory ICP mechanisms. Not all patients present with clear lucid intervals; some have continuous altered consciousness from the outset, while others may be relatively alert initially and deteriorate more gradually. The duration of lucid interval varies from minutes to hours and occasionally extends to days in slowly accumulating epidural collections.

• Ipsilateral pupillary dilation ("blown pupil"): This pathognomonic sign results from compression of the oculomotor nerve (CN III) at the tentorial edge as uncal herniation progresses. The parasympathetic fibers in CN III that innervate the pupillary sphincter are located peripherally in the nerve and are compressed first, leading to unopposed sympathetic pupil dilation. Initially the dilated pupil may still react sluggishly to light, but with progressive herniation it becomes completely nonreactive. This sign localizes the mass effect to the ipsilateral side and indicates neurosurgical emergency.

• Contralateral motor weakness and hyperreflexia: As the hematoma expands and shifts midline structures, the contralateral cerebral peduncle is compressed against the contralateral tentorial edge, affecting corticospinal tract fibers and producing contralateral hemiparesis. Weakness may be subtle initially (mild grip strength difference) but progresses to complete hemiplegia with herniation. This occurs contralateral to the hematoma because crossed pyramidal fibers in the cerebral peduncle are affected. Hyperreflexia and hypertonicity develop as upper motor neuron signs progress.

• Headache: Patients who remain conscious typically report severe headache, often described as explosive or "worst headache of my life" quality, reflecting acute elevation of ICP and meningeal irritation from the bleeding. Neck stiffness may be present due to meningeal irritation and blood irritating meninges.

• Vomiting: Central herniation-related vomiting may develop as ICP increases and brainstem structures become compressed. Unlike vomiting with gastric causes, this is projectile in nature and may occur without preceding nausea.

• Progressive unresponsiveness and brainstem signs: Untreated EDH progresses to complete loss of consciousness, loss of brainstem reflexes (corneal, gag), decorticate then decerebrate posturing, respiratory depression, and ultimately cardiopulmonary arrest if decompression is not performed. Cushing's triad (hypertension, bradycardia, irregular respiration) represents a late sign of severe increased ICP and imminent herniation.

• Physical examination findings in acute phase: Patients may display Battle's sign (bruising behind ears suggesting temporal bone fracture where middle meningeal artery runs) or raccoon eyes (periorbital ecchymosis), though these are not specific to EDH. The hematoma may palpable as a bulging fontanelle in infants. Focal neurologic examination abnormalities should be documented serially to assess progression.

• Important clinical variants: Delayed or occult EDH may present with gradual symptom onset over days in slowly bleeding cases, particularly with partial dural tears allowing slow accumulation. Bilateral EDH is unusual but catastrophic, occurring in severe polytrauma and requiring staged or simultaneous bilateral craniectomies. Posterior fossa EDH classically presents with ataxia, headache, and brainstem signs rather than typical temporal lobe compression findings.

• Clinical suspicion based on mechanism and presentation: The diagnosis should be suspected in any patient with acute head trauma followed by lucid interval and deterioration. The classic teaching case of EDH—initial unconsciousness, apparent recovery with normal conversation and behavior, then sudden decline into coma—is virtually pathognomonic. High-risk presentation includes any patient with significant head trauma, especially those on anticoagulation or with coagulopathy. Loss of consciousness followed by even brief lucidity followed by altered mental status should trigger immediate imaging.

• Non-contrast CT head imaging (gold standard): CT is the diagnostic study of choice and demonstrates characteristic findings. EDH appears as a hyperdense (bright white) lens-shaped or biconvex collection bounded by dural attachments at the falx and tentorium, creating a curved outer margin conforming to the inner skull table. The collection does not cross the midline or cross dural folds (distinguishing it from subdural hematoma, which crosses suture lines). Sensitivity of CT for EDH is >95% when performed in the acute setting. Midline shift, effacement of cisterns, and compression of lateral ventricles indicate significant mass effect. The hematoma density may be heterogeneous if active bleeding is occurring (density >75 Hounsfield units indicates fresh blood, while older blood is less dense).

• CT angiography (CTA) for treatment planning: CTA of the head demonstrates the source vessel in many cases and helps identify active extravasation ("blush") indicating ongoing bleeding. Blush sign correlates with increased expansion rates and need for urgent surgical intervention. CTA also identifies associated injuries like subdural hematoma, traumatic subarachnoid hemorrhage, or contusions that may affect management.

• MRI for subacute/chronic presentations: While CT is preferred acutely due to speed, MRI is excellent for dating hemorrhage and detecting subacute EDH. Acute blood appears hyperintense on T2 and FLAIR sequences, while chronic subdural hematomas may be isointense to brain making CT superior for acute diagnosis. MRI is not practical in the acute setting due to time requirements and compatibility issues with monitoring equipment.

• Diagnostic criteria and thresholds for intervention: There is no absolute volume threshold for intervention, as clinical symptoms and mass effect are more predictive than hematoma size alone. However, EDH >30 mL, thickness >15 mm, or midline shift >5 mm typically requires urgent surgical evacuation. Small EDH (<30 mL, <10-15 mm thickness, no significant mass effect) in neurologically intact patients may be managed conservatively with close neuromonitoring. The Glasgow Coma Scale (GCS) score prognostically predicts outcome: GCS 14-15 has excellent prognosis with appropriate treatment, while GCS ≤8 indicates severe injury with worse outcome despite intervention.

• Serial neurologic examination and repeat imaging: Patients managed conservatively require serial neurologic exams every 4-6 hours and repeat CT at 12-24 hours to assess for hematoma expansion. Any deterioration in consciousness, development of lateralizing signs (pupil changes, weakness), or increasing hematoma size on repeat imaging mandates urgent surgical intervention. Absence of deterioration over 48-72 hours in a neurologically intact patient generally favors continued conservative management.

• Differential diagnosis considerations: Acute subdural hematoma presents similarly but typically crosses suture lines and has a crescent shape rather than lens shape, and often occurs with more prominent associated parenchymal injury. Traumatic subarachnoid hemorrhage appears as blood in the subarachnoid spaces. Contusion shows hypodensity with surrounding edema. Epidural abscess develops over days-weeks in infection context (often post-neurosurgery or with bacteremia). Arteriovenous malformation may bleed spontaneously without trauma history.

• Urgent surgical evacuation as definitive treatment: Emergency craniotomy or burr hole evacuation is the definitive treatment for symptomatic EDH and represents a neurosurgical emergency requiring operating room availability within minutes to hours of diagnosis. The procedure involves creating access to the epidural space, evacuating clot, achieving hemostasis (typically by cautery of bleeding dural vessels), and ensuring no residual hematoma remains. Burr hole evacuation is faster and can be lifesaving in deteriorating patients when CT is being obtained, while formal craniotomy allows better hemostasis control and management of associated injuries. No medical therapy halts hematoma expansion once begun; surgical decompression is time-critical with mortality dramatically increasing for delays >4 hours from diagnosis.

• Preoperative stabilization and ICP management: While arranging emergent surgery, head elevation to 30 degrees reduces ICP by improving venous drainage. Maintain normothermia, normocapnia (PaCO2 35-40 mmHg by hyperventilation), and normoxia to optimize cerebral perfusion pressure. Osmotic therapy with mannitol (0.25-1 g/kg IV bolus) or hypertonic saline (3% bolus) temporizes increased ICP while surgical team prepares. Mannitol works via osmotic gradient to extract fluid from brain parenchyma into vasculature; hypertonic saline additionally provides immunomodulatory benefits. Avoid hyperthermia, hypoxia, and hypercarbia as these worsen ICP. Avoid hypotonic fluids; maintain euvolemia with isotonic crystalloid (normal saline or Lactated Ringer's).

• Anticoagulation reversal in appropriate patients: If the patient is on warfarin, immediately administer fresh frozen plasma (10-15 mL/kg) or prothrombin complex concentrate (PCC: 25 units/kg; preferred over FFP) to restore factors II, VII, IX, X and reverse anticoagulation. If on direct thrombin inhibitors (dabigatran), administer idarucizumab (5 g IV) which directly binds and inactivates dabigatran. For Factor Xa inhibitors (rivaroxaban, apixaban), use andexanet alfa or consider PCC as bridging if specific reversal unavailable. For aspirin or other antiplatelet agents, platelet transfusion (1 unit per 5-10 kg body weight) may be considered though evidence is limited. These reversal agents must be given urgently but do not replace surgical evacuation.

• Conservative management for select small hematomas: Small asymptomatic EDH (<30 mL, <10 mm thickness, GCS 14-15, no mass effect) in neurologically intact patients may be managed conservatively with **ICU/high-acuity monitoring, serial neurologic exams every 4-6 hours, and repeat

Neurologic emergencies

• Uncal transtentorial herniation: continued arterial expansion drives the medial temporal lobe over the tentorial edge; heralded by an ipsilateral sluggish then fixed dilated pupil, contralateral hemiparesis, and Cushing's triad (hypertension, bradycardia, irregular respirations). Immediate operative decompression is the only definitive maneuver — osmotherapy only buys minutes.
• Kernohan notch phenomenon: the contralateral cerebral peduncle is crushed against the opposite tentorial edge, producing hemiparesis ipsilateral to the clot — a false localizing sign. Never let the motor exam override CT lateralization.
• Posterior fossa EDH: small volumes compress the fourth ventricle → obstructive hydrocephalus and sudden apnea; signaled by rapidly worsening headache, ataxia, and depressed respiration.
• Re-accumulation after evacuation: bleeding from a fractured diploic edge or unligated meningeal vessel; any post-op decline in GCS or new pupillary asymmetry mandates immediate repeat non-contrast CT and return to the OR.

Delayed disease complications

• Posterior cerebral artery infarction: the herniating uncus compresses the PCA against the tentorium → occipital infarct with contralateral homonymous hemianopia (macular sparing).
• Post-traumatic seizures: cortical irritation from blood and contusion. Brain Trauma Foundation guidelines support short-course prophylaxis (phenytoin or levetiracetam) to reduce early seizures; it does not prevent late epilepsy.
• Basilar skull fracture sequelae: CSF otorrhea/rhinorrhea (confirm with beta-2 transferrin) with risk of meningitis; also traumatic coagulopathy/DIC from brain tissue factor release, marked by diffuse oozing and falling fibrinogen.

Treatment-related

• Osmotic therapy: mannitol causes osmotic diuresis with hypovolemia, hypotension (lowering cerebral perfusion pressure), hypernatremia and acute kidney injury; hypertonic saline can cause hyperchloremic metabolic acidosis. Follow serum sodium and osmolality.
• Hyperventilation: excessive hypocapnia constricts cerebral vessels and causes ischemia; Brain Trauma Foundation guidance is against prophylactic aggressive hyperventilation, reserving it as a brief bridge to surgery.
• Operative and ICU complications: wound infection or bone flap osteomyelitis, tension pneumocephalus (Mount Fuji sign on CT — an emergency), and venous thromboembolism from immobility, with prophylaxis timing decided by neurosurgery once hemostasis is secure.

• The stem's giveaway triad: blunt temporal/lateral head trauma → brief loss of consciousness → lucid interval → rapid decline with an ipsilateral "blown pupil." If the vignette gives a biconvex hyperdensity, the answer is epidural hematoma regardless of how minor the trauma sounds.
• Anatomy examiners actually test: the pterion (junction of frontal, parietal, temporal, sphenoid bones) is the thinnest part of the skull and overlies the middle meningeal artery, a branch of the maxillary artery entering through the foramen spinosum. A temporal bone fracture line crossing this groove is the classic pairing.
• Shape rule: epidural blood is lens-shaped and stops at cranial suture lines because the dura is fused to bone there; subdural blood is crescentic and crosses sutures but is limited by the falx. Use the shape, not the size, to answer.
• Single best next step: emergent non-contrast head CT. If the patient is already herniating (fixed dilated pupil, posturing), the answer shifts to airway protection and immediate neurosurgical evacuation — not MRI, not CTA, and never lumbar puncture, which risks precipitating herniation.
• Localization pearl: pupil dilation is ipsilateral to the clot (CN III compression), weakness is contralateral (peduncle). The distractor is Kernohan notch — ipsilateral weakness from the opposite peduncle striking the tentorium — a false localizing sign.
• Prognosis distractor: EDH has the best outcome of all traumatic intracranial mass lesions if evacuated before coma develops, because the underlying brain is often uninjured; acute subdural hematoma carries far higher mortality from associated parenchymal injury. Do not assume "arterial bleed = worse prognosis."
• Anticoagulation: reverse urgently but never in place of surgery — four-factor PCC for warfarin, idarucizumab for dabigatran, andexanet alfa for factor Xa inhibitors.
• Pediatric flag: an infant with EDH and no plausible mechanism warrants a child abuse evaluation, including skeletal survey and dilated fundoscopy, per American Academy of Pediatrics guidance.