Concussion and Other Traumatic Brain Injuries¶
Chapter 454 | Part 13: Neurologic Disorders
KEY CLINICAL POINTS¶
- Concussion is a mild traumatic brain injury (mTBI) characterized by transient neurological dysfunction without structural brain damage.
- Glasgow Coma Scale (GCS) is the primary tool for grading TBI severity (score range: 3–15).
- Mild TBI accounts for 70–90% of all TBI cases, with 85% of patients recovering fully within 1–2 weeks.
- Chronic subdural hematoma (CSDH) is a delayed complication of head injury, often managed with surgical evacuation.
- Traumatic axonal injury (TAI) is the most common injury in TBI, associated with diffuse white matter damage and microhemorrhages.
1. DEFINITION & OVERVIEW¶
Traumatic brain injury (TBI) is defined as an alteration in brain function or evidence of brain pathology caused by external force. Mild TBI (concussion) involves transient neurological dysfunction without structural damage. Severe TBI includes prolonged unconsciousness, amnesia, or neurologic deficits. The Glasgow Coma Scale (GCS) is the primary tool for grading severity (score range: 3–15).
Table 454-1 Glasgow Coma Scale¶
| EYE OPENING (E) | VERBAL RESPONSE (V) | BEST MOTOR RESPONSE (M) |
|---|---|---|
| Spontaneous | Oriented | Obeying commands |
| To speech | Confused | Localizing |
| To pressure | Words | Normal flexion |
| None | Sounds | Abnormal flexion |
| None | None | Extension |
| None | None |
1.1 TBI Classification¶
TBI severity is classified as mild (GCS 13–15), moderate (GCS 9–12), or severe (GCS 3–8). Mild TBI accounts for 70–90% of cases, with 85% of patients recovering fully within 1–2 weeks. Chronic subdural hematoma (CSDH) is a delayed complication of head injury, often managed with surgical evacuation.
1.2 Common Mechanisms¶
Common mechanisms include motor vehicle accidents, falls, assaults, and sports-related injuries. Blast injuries and penetrating trauma are also significant causes. Unintentional falls and motor vehicle crashes are the most common causes in the general population.
2. EPIDEMIOLOGY¶
TBI is a significant global health problem, with 2.5–4.8 million cases annually in the U.S. Age-specific rates show a bimodal distribution, with highest risk in younger individuals and older adults. Motor vehicle accidents are the leading cause in young adults, while falls are the primary cause in older adults. Nonfatal TBI-related hospitalization rates are comparable across racial groups.
2.1 Risk Factors¶
Risk factors include male sex (for young adults), female sex (for older adults), alcohol use, and prior TBI history. Sports participation, military service, and occupational hazards increase risk of repetitive head impacts.
2.2 Demographics¶
Young adults (15–34 years) and older adults (>65 years) have the highest incidence. Males are more likely to sustain TBI from motor vehicle accidents, while females are more likely to experience falls-related injuries.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
TBI results from mechanical forces causing brain injury, including direct trauma, acceleration/deceleration forces, and blast injuries. Pathophysiology involves primary injury (immediate mechanical damage) and secondary injury (ischemia, inflammation, and edema). Traumatic axonal injury (TAI) is the most common injury, characterized by microhemorrhages and diffuse white matter damage.
3.1 Injury Mechanisms¶
Mechanisms include coup-contrecoup injuries, penetrating trauma, and blast-induced brain injury. Acceleration/deceleration forces cause shearing of axons and microhemorrhages. Penetrating injuries may cause focal damage with high mortality.
3.2 Pathophysiology¶
Primary injury includes contusions, hematomas, and axonal shearing. Secondary injury involves cerebral edema, intracranial hypertension, and neuroinflammation. TBI can lead to long-term neurodegeneration and increased risk of dementia.
4. CLINICAL FEATURES¶
Clinical features vary by TBI severity. Mild TBI presents with headache, dizziness, and transient amnesia. Moderate/severe TBI may involve prolonged unconsciousness, focal neurological deficits, and increased intracranial pressure. Postconcussive symptoms (PPCS) include fatigue, dizziness, and cognitive impairment.
4.1 Mild TBI¶
Symptoms include headache, dizziness, nausea, and brief amnesia. Most patients recover within 1–2 weeks. Persistent symptoms may indicate PPCS or more severe injury.
4.2 Severe TBI¶
Features include prolonged unconsciousness (>30 minutes), focal neurological deficits, and increased intracranial pressure. May present with seizures, hemiparesis, or cranial nerve injuries.
5. DIFFERENTIAL DIAGNOSIS¶
Differential diagnoses include concussion, intracranial hemorrhage, meningitis, and psychiatric disorders. Headache and dizziness may mimic migraines or vestibular disorders. Persistent symptoms may overlap with chronic traumatic encephalopathy (CTE) or postconcussive syndrome.
5.1 Non-Neurological Causes¶
Consider migraines, inner ear disorders, and psychiatric conditions (e.g., depression, anxiety) in patients with persistent symptoms. Drug intoxication may mimic TBI symptoms.
5.2 Other Brain Injuries¶
Differentiate between concussion, subdural hematoma, and intracranial tumors. Imaging is critical for distinguishing between these conditions.
6. INVESTIGATIONS & DIAGNOSIS¶
Diagnosis relies on clinical evaluation, imaging (CT/MRI), and biomarkers. CT is the primary imaging modality for acute TBI, while MRI detects subtle injuries. Blood-based biomarkers (e.g., GFAP, UCHL1) improve detection of mild TBI.
6.1 Imaging¶
Noncontrast CT is first-line for acute TBI. 3T MRI detects microhemorrhages and white matter changes. CT is less sensitive for mild TBI but useful for detecting hematomas.
6.2 Biomarkers¶
Blood-based biomarkers (GFAP, UCHL1) show promise for detecting TBI and predicting outcomes. MRI with gradient-echo sequences improves detection of microhemorrhages in mild TBI.
7. MANAGEMENT & TREATMENT¶
Management includes immediate resuscitation, surgical intervention for hematomas, and rehabilitation for long-term recovery. Pharmacologic treatment addresses symptoms like headache, seizures, and spasticity. Cognitive and physical rehabilitation is critical for functional recovery.
7.1 Acute Management¶
Stabilize airway, breathing, and circulation. Use low-molecular-weight heparin for anticoagulation. Surgical evacuation is required for large hematomas or increased ICP.
7.2 Chronic Management¶
Rehabilitation includes cognitive therapy, vestibular exercises, and subthreshold exercise for PPCS. Medications like acetaminophen, amitriptyline, and promethazine may be used for symptoms.
8. PROGNOSIS & COMPLICATIONS¶
Most mild TBI patients recover fully within weeks. Severe TBI may result in long-term disability or death. Complications include chronic subdural hematoma, posttraumatic epilepsy, and increased dementia risk. Long-term outcomes depend on injury severity and recovery trajectory.
8.1 Long-Term Outcomes¶
TBI increases risk of dementia (63–96% higher) and neurodegenerative diseases. Chronic traumatic encephalopathy (CTE) is associated with repetitive head impacts and tau protein deposition.
8.2 Complications¶
Complications include posttraumatic epilepsy (17% of contusion cases), chronic subdural hematoma, and cognitive decline. Early rehabilitation reduces risk of prolonged recovery.
9. SPECIAL CONSIDERATIONS¶
Special considerations include management of TBI in pregnancy, pediatrics, and the elderly. Sports-related concussions require strict return-to-play protocols. Military and veteran populations may have unique risks for repetitive head injury.
9.1 Pediatric Considerations¶
Children are prone to prolonged symptoms and delayed recovery. Imaging should be used cautiously due to radiation risks. Cognitive and behavioral changes may persist beyond acute recovery.
9.2 Sports-Related Concussions¶
Return-to-play guidelines emphasize symptom resolution and medical clearance. Early rehabilitation with subthreshold exercise reduces recovery time. Second-impact syndrome is a risk with repeated concussions.
10. KEY POINTS & CLINICAL PEARLS¶
Key points: 1) Mild TBI is common, with 85% of patients recovering fully within 1–2 weeks. 2) CT is the primary imaging modality for acute TBI. 3) Chronic subdural hematoma requires surgical evacuation. 4) Blood-based biomarkers improve detection of mild TBI. 5) Early rehabilitation reduces risk of prolonged recovery.