Neurology · Traumatic Brain Injury
The facts most likely to be tested
The Canadian CT Head Rule mandates a non-contrast head CT for patients with GCS < 15 two hours post-injury, suspected open skull fracture, or signs of basilar skull fracture.
Epidural hematoma classically presents with a lucid interval following a temporal bone fracture and middle meningeal artery rupture, appearing as a biconvex (lens-shaped) hyperdensity on CT.
Subdural hematoma results from the tearing of bridging veins and appears as a crescent-shaped hyperdensity that crosses suture lines on non-contrast head CT.
Cushing's triad—consisting of hypertension, bradycardia, and irregular respirations—is a late sign of elevated intracranial pressure (ICP) and impending brain herniation.
Initial management of elevated ICP includes head of bed elevation to 30 degrees, hyperventilation (to induce hypocapnia/vasoconstriction), and hyperosmolar therapy with mannitol or hypertonic saline.
Diffuse axonal injury is characterized by loss of consciousness following high-velocity deceleration and shows punctate hemorrhages at the gray-white matter junction on MRI.
Prophylactic phenytoin or levetiracetam is indicated for the prevention of early post-traumatic seizures (within 7 days) in patients with severe TBI.
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A 24-year-old male is brought to the ED after a motorcycle accident. He was initially unconscious, then regained consciousness for 30 minutes, but is now obtunded with a dilated, non-reactive pupil on the right side. Physical exam reveals a boggy hematoma over the right temporal region. A non-contrast head CT shows a biconvex hyperdensity that does not cross suture lines. His blood pressure is 170/95 mmHg, heart rate is 52 bpm, and respiratory rate is 10/min.
What is the most appropriate next step in management?
Urgent surgical decompression (craniotomy)
The patient exhibits signs of an epidural hematoma with impending herniation (Cushing's triad and fixed pupil), requiring immediate surgical evacuation to relieve intracranial pressure.
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Etiology / Epidemiology
Primary causes include falls, motor vehicle accidents, and assaults. High-risk groups include the elderly and those on anticoagulants.
Clinical Manifestations
Look for lucid interval in epidural hematoma. GCS < 8 indicates need for intubation.
Diagnosis
Non-contrast CT head is the gold standard. Midline shift > 5mm is a surgical emergency.
Treatment
Maintain CPP 60-70 mmHg. Use Mannitol for elevated ICP. Avoid prophylactic phenytoin.
Prognosis
Monitor for post-concussive syndrome. GCS score at admission is the strongest predictor of mortality.
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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 dominates in younger populations. Patients on antiplatelet or anticoagulant therapy are at extreme risk for intracranial hemorrhage even after minor trauma.
Pertinent Anatomy
The pterion is the site of the middle meningeal artery, prone to rupture in epidural hematomas. The tentorium cerebelli separates the cerebrum from the cerebellum; herniation here causes uncal herniation and CN III palsy.
Pathophysiology
Primary injury occurs at impact, while secondary injury results from hypoxia, hypotension, and cerebral edema. The Monro-Kellie doctrine dictates that the sum of intracranial volumes (brain, blood, CSF) is constant; expansion of one requires reduction of others to prevent herniation.
Clinical Manifestations
Epidural hematoma presents with a lucid interval followed by rapid decline. Subdural hematoma is common in the elderly due to bridging vein rupture. Cushing's triad (hypertension, bradycardia, irregular respirations) signals impending herniation.
Diagnosis
Non-contrast CT head is the initial study of choice for all acute TBI. MRI brain is superior for detecting diffuse axonal injury. A midline shift > 5mm on imaging typically mandates immediate neurosurgical consultation.
Treatment
Initial management focuses on the ABCDEs to prevent secondary brain injury. Mannitol or hypertonic saline are used to reduce elevated ICP. Avoid hypotonic fluids as they exacerbate cerebral edema. Hyperventilation (target PaCO2 30-35 mmHg) is a temporary bridge to surgery.
Prognosis
Long-term sequelae include post-concussive syndrome and cognitive impairment. GCS < 8 is the standard threshold for intubation and aggressive ICP monitoring.
Differential Diagnosis
Epidural Hematoma: lucid interval
Subdural Hematoma: bridging vein rupture
Subarachnoid Hemorrhage: thunderclap headache
Diffuse Axonal Injury: coma out of proportion to CT findings
Concussion: normal CT head