- Pathophysiology/Etiology
- A functional brain injury caused by biomechanical forces (direct blow or acceleration-deceleration) that induce shear stress on brain tissue.
- Involves a complex neurometabolic cascade, not a gross structural injury.
- Key events include:
- Ionic Flux: Abrupt, indiscriminate neuronal firing leads to K+ efflux and Ca2+ influx.
- Energy Crisis: Cellular pumps work overtime to restore ionic balance, consuming massive amounts of ATP, while cerebral blood flow is simultaneously reduced, creating a metabolic mismatch.
- This metabolic disturbance, not structural damage, underlies the clinical symptoms.
- Clinical Presentation
- Symptoms are diverse and can be subtle, sometimes delayed for hours or days. They fall into four main categories:
- Physical: Headache (most common symptom), nausea/vomiting, dizziness, balance problems, visual disturbances (blurry vision), sensitivity to light/noise.
- Cognitive: Confusion (“feeling in a fog”), difficulty concentrating, anterograde or retrograde amnesia, slowed processing speed.
- Emotional: Irritability, anxiety, depression, mood swings.
- Sleep: Drowsiness, sleeping more or less than usual, trouble falling asleep.
- GCS is typically 13-15. Loss of consciousness occurs in <10% of cases and is not required for diagnosis.
- Diagnosis
- Primarily a clinical diagnosis based on a history of trauma and characteristic symptoms.
- Neuroimaging (CT/MRI): Typically normal. Its main role is to rule out more severe injury (e.g., intracranial hemorrhage, skull fracture) if red flags are present.
- Red Flags Requiring Emergent Imaging: GCS <15, focal neurologic deficits, persistent vomiting, worsening headache, seizure, or signs of basilar skull fracture (e.g., raccoon eyes, Battle sign).
- Standardized assessment tools (e.g., SCAT5) can aid in diagnosis and monitoring but are not solely diagnostic.
- Differential Diagnostics
- It is crucial to rule out more severe traumatic brain injuries:
- Epidural Hematoma (EDH): Lucid interval followed by rapid neurologic decline. Biconvex (lentiform) shape on CT that does not cross suture lines. Laceration of the middle meningeal artery is classic.
- Subdural Hematoma (SDH): Tearing of bridging veins. Crescent-shaped hemorrhage on CT that can cross suture lines. More common in the elderly and alcoholics.
- Subarachnoid Hemorrhage (SAH): “Worst headache of life.” Can be traumatic or from a ruptured aneurysm.
- Intracerebral Hemorrhage: Bleeding within the brain parenchyma.
- Management
- The cornerstone is physical and cognitive rest for the initial 24-48 hours to reduce metabolic stress on the brain.
- Gradual Return to Activity: After the initial rest period, a stepwise increase in physical and cognitive activity is initiated. The patient should proceed to the next step only if the current one is tolerated without symptom exacerbation.
- Return-to-Play protocol for athletes is strict: an athlete with a suspected concussion must be immediately removed from play and cannot return the same day. They must be symptom-free and receive medical clearance before starting the graduated return protocol.
- Symptomatic treatment for headaches may include analgesics like acetaminophen.
- Key Associations/Complications
- Post-Concussion Syndrome (PCS): Persistence of concussion symptoms (e.g., headache, dizziness, cognitive impairment) for weeks to months (typically >3 months) after the initial injury.
- Second Impact Syndrome (SIS): A rare but catastrophic event where a second concussion occurs before the brain has recovered from the first. It can lead to rapid, diffuse cerebral edema, brain herniation, and death. This highlights the critical importance of adhering to return-to-play protocols.
- Chronic Traumatic Encephalopathy (CTE): A progressive neurodegenerative disease associated with a history of repetitive head trauma. Characterized by the deposition of tau protein.