What are the differential diagnoses for a patient with a head injury?

Differential Diagnoses for Head Injury

The differential diagnosis for head injury must be stratified by severity using the Glasgow Coma Scale (GCS 13-15 for mild, 9-12 for moderate, 3-8 for severe), with immediate focus on identifying life-threatening intracranial pathology requiring neurosurgical intervention versus functional injury without structural damage. 1

Primary Structural Intracranial Injuries

Hemorrhagic Lesions

• Epidural hematoma: Classic presentation with brief loss of consciousness followed by lucid interval then deterioration; look for temporal bone fracture and middle meningeal artery injury 2, 1
• Subdural hematoma: More common in elderly and those on anticoagulation; presents with progressive decline in consciousness; smear subdurals <4mm thick may be clinically unimportant 2
• Subarachnoid hemorrhage: Localized blood <1mm thick may be clinically unimportant, but thicker collections require monitoring 2
• Intracerebral contusion: Actual parenchymal damage requiring neuroimaging for diagnosis; solitary contusions <5mm may be clinically unimportant 2, 1
• Intraventricular hemorrhage: Associated with more severe injury and worse prognosis 1

Non-Hemorrhagic Structural Injuries

• Diffuse axonal injury: Occurs with rotational forces; may show microhemorrhages on susceptibility-weighted MRI sequences; associated with worse long-term cognitive outcomes 3, 2
• Cerebral edema: Can develop hours to days post-injury; monitor for signs of increased intracranial pressure 1, 4
• Skull fractures: Basilar skull fractures (Battle's sign, raccoon eyes, hemotympanum, CSF rhinorrhea/otorrhea) significantly increase risk of intracranial injury; depressed fractures through inner table require neurosurgical evaluation 2, 1
• Pneumocephalus: Isolated pneumocephalus may be clinically unimportant unless associated with other injuries 2

Functional Injury Without Structural Damage

Concussion/Mild Traumatic Brain Injury

• Concussion: By definition shows no structural abnormality on standard neuroimaging; results from neurometabolic cascade with increased energy demand and decreased cerebral blood flow 1, 5
• Post-concussive syndrome: Occurs in 15-20% of mild TBI patients beyond 2 weeks; most common symptoms include headaches, memory difficulties, dizziness, fatigue, sleep disruption, and impaired cognition 1, 5, 6

Vascular Complications

• Traumatic aneurysm or pseudoaneurysm: Consider with skull base fractures through vascular channels; requires CTA or MRA for detection 2
• Arteriovenous fistula: Can develop after penetrating or severe blunt trauma; may present with delayed symptoms 2
• Carotid or vertebral artery dissection: Consider with neck trauma component; presents with focal neurologic deficits or stroke symptoms 2
• Venous sinus thrombosis: Can occur with fractures near sagittal sinus; requires MRV or CTV evaluation 2

Secondary Complications and Mimics

Early Complications (Hours to Days)

• Cerebral herniation: Dilated fixed pupil indicates uncal herniation with third nerve compression; bilateral pinpoint pupils suggest pontine involvement 4
• Seizures: Post-traumatic seizures occur in small percentage; document as high-risk feature requiring CT 2
• Meningitis: Consider with basilar skull fracture, CSF leak, or penetrating injury 2

Late Complications (Weeks to Months)

• Chronic subdural hematoma: Particularly in elderly, alcoholics, or anticoagulated patients; may present weeks after seemingly minor trauma 2
• Hydrocephalus: Can develop from subarachnoid hemorrhage or intraventricular blood 1
• Leptomeningeal cyst ("growing fracture"): Rare complication in young children with skull fractures 2
• Chronic traumatic encephalopathy: Consider with history of repetitive mild TBI; associated with behavioral changes, executive dysfunction, memory loss progressing over decades 3

Non-Traumatic Mimics Requiring Exclusion

• Stroke: Acute diplopia or focal deficits may represent posterior circulation stroke rather than traumatic injury 2
• Intracranial tumor: Can present after minor trauma that brings patient to medical attention; MRI superior for detection 2
• Infection (abscess, encephalitis): Consider with fever, altered mental status disproportionate to injury 2
• Metabolic encephalopathy: Hypoglycemia, hyponatremia, hepatic encephalopathy can mimic or complicate head injury 1
• Intoxication: Alcohol or drug intoxication present in significant percentage of head injury patients; does not exclude structural injury 2

Critical High-Risk Features Mandating Immediate CT

Any of the following features require immediate non-contrast head CT: 2, 1

• Failure to reach GCS 15 within 2 hours of injury
• Suspected open or depressed skull fracture
• Signs of basilar skull fracture (Battle's sign, raccoon eyes, hemotympanum, CSF leak)
• Vomiting more than once
• Age >64 years (>60 years in some criteria)
• Post-traumatic seizure
• Focal neurologic deficit
• Coagulopathy or anticoagulant therapy
• Dangerous mechanism of injury (pedestrian struck, ejection from vehicle, fall >3 feet or 5 stairs)

Common Pitfalls to Avoid

• Never assume clinical improvement means radiographic stability: Delayed hematoma expansion can occur; repeat imaging is often necessary with clinical deterioration 1
• Never discharge without appropriate imaging when high-risk features present: Even patients with GCS 15 can have clinically important brain injury requiring neurosurgery (1.7% in one study) 2
• Never rely on skull radiographs: They are insufficient to detect intracranial pathology and should not be used 2
• Never ignore neck injury: Cervical spine injury should be actively sought in head trauma patients 7
• Never assume litigation prolongs symptoms: Most patients with persistent post-concussive symptoms have genuine complaints regardless of compensation status 6, 7