Neurology · Traumatic Brain Injury
The facts most likely to be tested
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An epidural hematoma typically results from a temporal bone fracture causing rupture of the middle meningeal artery, presenting with a lucid interval followed by rapid neurologic decline.
A subdural hematoma is caused by the tearing of bridging veins and appears as a crescent-shaped hyperdensity on non-contrast CT that crosses suture lines but not dural reflections.
A subarachnoid hemorrhage following trauma presents with thunderclap headache and meningismus due to blood in the CSF space.
Cerebral contusions are most commonly located in the frontal and temporal lobes and are characterized by the coup-contrecoup mechanism of injury.
Diffuse axonal injury occurs due to rotational acceleration-deceleration forces and presents with punctate hemorrhages at the gray-white junction on MRI.
The Glasgow Coma Scale (GCS) is the standard for assessing level of consciousness, where a score of 8 or less mandates endotracheal intubation for airway protection.
Cushing's triad—consisting of hypertension, bradycardia, and irregular respirations—is a late sign of elevated intracranial pressure and impending brain herniation.
Vignette unlocked
A 24-year-old male is brought to the ED after being struck in the head with a baseball bat. He was briefly unconscious, then regained consciousness and felt 'fine' for 45 minutes before becoming obtunded and hemiparetic. Physical exam reveals a dilated pupil on the side of the injury. A non-contrast head CT shows a biconvex, lens-shaped hyperdensity that does not cross suture lines.
What is the most likely diagnosis?
Epidural hematoma
The vignette describes the classic presentation of an epidural hematoma, which is tested in Bet #1, characterized by a lucid interval and a biconvex hematoma due to middle meningeal artery rupture.
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High yield triage
Etiology / Epidemiology
Primary causes include falls, motor vehicle accidents, and assaults. High-risk groups include the elderly on anticoagulants and contact sports athletes.
Clinical Manifestations
Look for lucid interval in epidural hematoma. GCS < 8 indicates need for intubation.
Diagnosis
Non-contrast CT head is the gold standard. GCS score is the primary clinical severity metric.
Treatment
Maintain CPP > 60 mmHg. Mannitol or hypertonic saline for elevated ICP. Give prophylactic phenytoin or levetiracetam for early (≤7 day) post-traumatic seizures in severe TBI.
Prognosis
Secondary injury prevention is critical. GCS 13-15 is mild TBI; GCS 3-8 is severe TBI.
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Epidemiology & Etiology
TBI is a leading cause of morbidity in young adults and the elderly. Falls are the most common cause in patients >65, while MVA predominate in younger cohorts. Patients on anticoagulants are at extreme risk for delayed intracranial hemorrhage even after minor trauma.
Pertinent Anatomy
The middle meningeal artery is the classic source of epidural hematoma following temporal bone fracture. The bridging veins are prone to shearing in subdural hematoma during rapid deceleration. The tentorium cerebelli acts as a rigid structure that can cause uncal herniation.
Pathophysiology
Primary injury occurs at the moment of impact via direct mechanical force. Secondary injury follows due to excitotoxicity, oxidative stress, and cerebral edema. Maintaining cerebral perfusion pressure (CPP) is vital to prevent ischemia, as the brain is highly sensitive to hypoxia and hypotension.
Clinical Manifestations
Assess for Battle sign (mastoid ecchymosis) or raccoon eyes (periorbital ecchymosis) suggesting basilar skull fracture. A lucid interval followed by rapid decompensation is pathognomonic for epidural hematoma. Cushing's triad (hypertension, bradycardia, irregular respirations) signals impending herniation.
Diagnosis
Non-contrast CT head is the gold standard for acute evaluation. Use the Canadian CT Head Rule or New Orleans Criteria to determine imaging necessity in mild TBI. GCS < 15 at 2 hours post-injury or GCS < 13 at any time warrants immediate imaging.
Treatment
Prioritize ABCDEs and cervical spine stabilization. For elevated ICP, elevate the head of the bed to 30 degrees and administer mannitol or hypertonic saline. Avoid steroids as they increase mortality in TBI. Avoid hypotension to maintain adequate cerebral perfusion.
Prognosis
Monitor for post-concussive syndrome including headache, dizziness, and cognitive impairment. Second impact syndrome is a rare but fatal complication of repeat injury. Long-term outcomes are stratified by the Glasgow Outcome Scale.
Differential Diagnosis
Epidural Hematoma: lucid interval and temporal bone fracture
Subdural Hematoma: crescent-shaped bleed crossing suture lines
Subarachnoid Hemorrhage: thunderclap headache and meningeal irritation
Intracerebral Hemorrhage: focal neurological deficits based on location
Diffuse Axonal Injury: coma out of proportion to CT findings