18.1 Concussion, Moderate-to-Severe TBI & Intracranial Injury

Glasgow Coma Scale & Traumatic Brain Injury Classification

Traumatic Brain Injury (TBI) is a major cause of death and lifelong disability globally. Clinical triage, monitoring, and therapeutic interventions are anchored to the Glasgow Coma Scale (GCS), which evaluates motor, verbal, and eye-opening responses. The GCS provides an objective measure of the depth of impaired consciousness, with scores ranging from 3 (deep coma or death) to 15 (fully awake, alert, and oriented).

Glasgow Coma Scale Components

Clinical Note: If an endotracheal tube is in place, the verbal score is designated as "1T" (e.g., GCS E3V1TM5 = GCS 9T).

Severity Stratification of TBI

1. Mild TBI / Concussion (GCS 13–15):
   • Represents ~80% of all traumatic brain injuries.
   • Patients are typically conscious upon presentation but may report transient loss of consciousness (LOC), retrograde or anterograde amnesia, confusion, dizziness, headache, or visual disturbances.
   • The primary diagnostic priority is identifying the small subset (5–10%) harboring acute neurosurgical intracranial hemorrhage requiring emergent intervention.
2. Moderate TBI (GCS 9–12):
   • Represents ~10% of presentations.
   • Characterized by marked confusion, somnolence, lethargy, or focal neurologic deficits.
   • Requires mandatory non-contrast head CT, trauma surgery/neurosurgical consultation, and admission to a high-acuity monitored setting or intensive care unit (ICU).
3. Severe TBI (GCS 3–8):
   • Represents ~10% of presentations and carries significant mortality (30–40%).
   • Patients are comatose and unable to protect their airway.
   • Cardinal Airway Mandate: "GCS 8 or less, intubate." Early definitive endotracheal intubation via Rapid Sequence Intubation (RSI) is critical to prevent fatal secondary hypoxemia and hypercapnic cerebral vasodilation.

Critical Resuscitation Goals in Severe TBI

Secondary brain injury occurs in the hours to days following the primary biomechanical insult. Clinical management focuses on maintaining adequate Cerebral Perfusion Pressure (CPP), calculated as: $\text{CPP} = \text{MAP} - \text{ICP}$ Normal intracranial pressure (ICP) is <15 mm Hg. In severe TBI, sustained ICP >20–22 mm Hg compromises cerebral perfusion and drives fatal brainstem herniation.

• Avoid Secondary Insults (The "H-Bombs" of TBI):
  • Hypotension: A single episode of Systolic Blood Pressure (SBP) <90 mm Hg doubles mortality. Target SBP ≥100 mm Hg for patients aged 50–69 years, or ≥110 mm Hg for patients aged 15–49 or ≥70 years, utilizing isotonic crystalloids and IV vasopressors (e.g., norepinephrine) if necessary.
  • Hypoxia: A single documented episode of PaO2 <60 mm Hg or SpO2 <90% dramatically worsens functional outcome. Maintain SpO2 ≥95%.
  • Hyperventilation / Hypocapnia: Routine aggressive hyperventilation is strictly contraindicated. Hypocapnia (PaCO2 <35 mm Hg) induces profound cerebral vasoconstriction, causing severe secondary ischemic cerebral infarction. Normocapnia (PaCO2 target 35–40 mm Hg) is maintained. Brief, temporary hyperventilation (PaCO2 target 30–35 mm Hg) is reserved exclusively as a temporary bridge during active uncal herniation while definitive osmotic therapy or craniotomy is prepared.
  • Hyperpyrexia: Maintain normothermia; elevated core temperature accelerates cerebral metabolic demand.
  • Hyperglycemia: Target blood glucose 140–180 mg/dL; avoid extremes of hypo- and hyperglycemia.

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Clinical Decision Rules for Urgent Head CT in Adults: CCHR & NOC

Liberal imaging of every minor head bump causes unnecessary ionizing radiation exposure, emergency department overcrowding, and financial cost. Validated clinical decision algorithms identify patients who can be safely discharged without neuroimaging.

The Canadian CT Head Rule (CCHR)

The CCHR applies to adult patients (age ≥16 years) with blunt minor head trauma who experienced witnessed loss of consciousness, definite amnesia, or witnessed disorientation, and present with a baseline GCS score of 13 to 15.

                     CANADIAN CT HEAD RULE (CCHR) ALGORITHM
                     
    ┌────────────────────────────────────────────────────────────────────────┐
    │ Inclusion: Minor Head Injury + (LOC, Amnesia, or Witnessed Confusion)   │
    │ Exclusions: Age <16, GCS <13, Anticoagulant use, Penetrating trauma    │
    └───────────────────────────────────┬────────────────────────────────────┘
                                        │
                                        ▼
    ┌────────────────────────────────────────────────────────────────────────┐
    │ HIGH-RISK CRITERIA (Need for Neurosurgical Intervention: ~100% Sens)   │
    │ 1. GCS <15 at 2 hours post-injury                                      │
    │ 2. Suspected open or depressed skull fracture                          │
    │ 3. Any clinical sign of basilar skull fracture:                        │
    │    • Hemotympanum (blood behind tympanic membrane)                     │
    │    • Battle sign (retroauricular/mastoid ecchymosis)                   │
    │    • Raccoon eyes (periorbital ecchymosis without facial trauma)       │
    │    • CSF otorrhea or CSF rhinorrhea                                    │
    │ 4. ≥2 episodes of vomiting                                             │
    │ 5. Age ≥65 years                                                       │
    └───────────────────────────────────┬────────────────────────────────────┘
                                        │
                     ┌──────────────────┴──────────────────┐
                     │ ANY High-Risk Present?              │
                     ├─────────────────┬───────────────────┤
                     │ YES             │ NO                │
                     ▼                 ▼                   │
        ┌─────────────────────────┐  ┌─────────────────────────────────────┐
        │ URGENT NON-CONTRAST     │  │ MEDIUM-RISK CRITERIA                │
        │ HEAD CT MANDATED        │  │ (Brain Injury on CT: ~98-100% Sens) │
        └─────────────────────────┘  │ 1. Retrograde amnesia ≥30 minutes   │
                                     │ 2. Dangerous mechanism of injury:   │
                                     │    • Pedestrian struck by vehicle   │
                                     │    • Occupant ejected from vehicle  │
                                     │    • Fall from height >3 ft (>5 sts)│
                                     └──────────────────┬──────────────────┘
                                                        │
                                     ┌──────────────────┴──────────────────┐
                                     │ ANY Medium-Risk Present?            │
                                     ├─────────────────┬───────────────────┤
                                     │ YES             │ NO (All Negative) │
                                     ▼                 ▼                   │
                        ┌─────────────────────────┐  ┌─────────────────────┐
                        │ URGENT NON-CONTRAST     │  │ HEAD CT NOT         │
                        │ HEAD CT MANDATED        │  │ INDICATED           │
                        └─────────────────────────┘  │ Safe for Discharge  │
                                                     └─────────────────────┘

• High-Risk Criteria (Predicting Need for Neurosurgical Intervention):
  1. GCS score <15 at 2 hours post-injury
  2. Suspected open or depressed skull fracture (e.g., scalp laceration over palpable bone step-off)
  3. Any clinical sign of basilar skull fracture:
     • Hemotympanum (violaceous blood pooling behind the intact tympanic membrane)
     • Battle's sign (ecchymosis over the mastoid process behind the ear; delayed appearance 12–36 hours)
     • "Raccoon eyes" (bilateral periorbital ecchymosis sparing the tarsal plate, without direct orbital trauma)
     • CSF rhinorrhea or otorrhea (clear fluid leak; positive "halo test" on filter paper, positive beta-2 transferrin)
  4. Two or more discrete episodes of vomiting
  5. Age ≥65 years (cerebral atrophy stretches bridging veins, predisposing to hemorrhage with minimal trauma)
• Medium-Risk Criteria (Predicting Clinically Important Brain Injury on CT): 6. Retrograde amnesia to the event of ≥30 minutes (inability to recall events immediately preceding impact) 7. Dangerous injury mechanism: Pedestrian struck by motor vehicle; occupant ejected from motor vehicle; fall from an elevation >3 feet (or >5 stairs)
• CCHR Exclusion Criteria: Patients with GCS <13, age <16 years, open penetrating injuries, bleeding diathesis, or therapeutic anticoagulation (warfarin, DOACs, LMWH). Exam Pearl: Any blunt head trauma patient on therapeutic anticoagulants or antiplatelet therapy requires an immediate non-contrast head CT regardless of a normal GCS or negative decision rules.

The New Orleans Criteria (NOC)

The New Orleans Criteria apply strictly to blunt head injury patients with a baseline GCS of 15. A non-contrast head CT is indicated if any of the following 7 criteria are present:

1. Headache
2. Vomiting
3. Age >60 years
4. Drug or alcohol intoxication
5. Deficits in short-term memory (persistent anterograde amnesia)
6. Physical evidence of trauma above the clavicles
7. Post-traumatic seizure Comparison: The CCHR has higher specificity than NOC, leading to lower imaging rates while maintaining near 100% sensitivity for neurosurgical lesions.

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Pediatric Head Trauma: The PECARN Decision Rules

Children have thinner cranial bones, larger head-to-body ratios, and developing brains that are particularly vulnerable both to traumatic shearing and to the carcinogenic risks of ionizing radiation. The Pediatric Emergency Care Applied Research Network (PECARN) criteria represent the most rigorously validated tool for ruling out clinically important traumatic brain injury (ciTBI)—defined as intracranial injury resulting in death, neurosurgery, intubation for >24 hours, or hospital admission for ≥2 nights.

PECARN Rule Structure (<2 Years vs ≥2 Years)

• Clinical Application of the Intermediate Group: In intermediate-risk children, observational monitoring for 4 to 6 hours in the emergency department is preferred over reflex CT. If symptoms (e.g., headache, vomiting, or behavior) improve, imaging can be safely omitted. CT is favored if intermediate features are multiple, symptoms worsen during observation, or the child is <3 months old.

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Extra-Axial Intracranial Hemorrhages: Epidural vs Subdural Hematoma

Extra-axial hemorrhages collect within the anatomical compartments surrounding the brain parenchyma. Differentiating epidural from subdural hematoma on clinical and radiological grounds is an essential board-exam competency.

Clinical and Radiographic Distinctions

               EPIDURAL HEMATOMA                  SUBDURAL HEMATOMA
               
                 Outer Skull                        Outer Skull
             ┌─────────────────┐                ┌─────────────────┐
             │   Calvarium     │                │   Calvarium     │
             ├─────────────────┤                ├─────────────────┤
             │                 │                │   DURA MATER    │
             │  (Arterial)     │                ├─────────────────┤
             │   BICONVEX /    │ Dura           │                 │
             │   LENTICULAR    │                │  (Venous)       │
             │   COLLECTION    │                │   CRESCENTIC    │ Arachnoid
             │                 │                │   COLLECTION    │
             ├─────────────────┤                │                 │
             │   DURA MATER    │                ├─────────────────┤
             ├─────────────────┤                │ ARACHNOID MATER │
             │    Brain Tissue │                │    Brain Tissue │
             └─────────────────┘                └─────────────────┘
             • Does NOT cross suture lines      • CROSSES cranial suture lines
             • Middle Meningeal Artery          • Bridging Cortical Veins

Uncal Herniation Syndrome

When an expanding extra-axial hematoma (most acutely an epidural hematoma) expands in the temporal fossa, it displaces the medial temporal lobe—specifically the uncus—inferomedially over the free edge of the tentorium cerebelli:

1. Ipsilateral CN III Compression: The uncus directly compresses the ipsilateral oculomotor nerve (CN III). Parasympathetic pupillary constrictor fibers run on the outer surface of CN III; their disruption causes an unreactive, fixed, and dilated pupil ("blown pupil"), followed by ptosis and a "down-and-out" eye.
2. Ipsilateral Cerebral Peduncle Compression: Compression of the descending corticospinal fibers in the ipsilateral crus cerebri produces contralateral hemiparesis or hemiplegia.
3. Kernohan's Notch Phenomenon (False Localizing Sign): Occasionally, the expanding mass shifts the midbrain laterally against the opposite tentorial edge, compressing the contralateral cerebral peduncle, resulting in hemiparesis ipsilateral to the hematoma.
4. Brainstem Compression: Downward displacement compresses the reticular activating system, precipitating deep coma, decerebrate posturing, and respiratory arrest.

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Concussion Diagnosis & Modern Active Recovery Protocols

A concussion is a traumatic brain injury induced by biomechanical forces that cause functional neurological disturbance rather than gross structural neuropathology. Standard structural neuroimaging (CT and routine MRI) is normal.

Pathophysiology: The Neurometabolic Cascade

Biomechanical shearing forces stretch neuronal membranes, initiating a complex cascade:

1. Indiscriminate Depolarization: Massive efflux of intracellular potassium ($K^+$) and influx of sodium and calcium ($Ca^{2+}$), triggering non-specific release of excitatory amino acids (glutamate).
2. Energy Crisis: Membrane ion pumps (Na+/K+-ATPase) consume excessive ATP to restore ionic equilibrium, driving a period of acute hyperglycolysis.
3. Cerebral Hypoperfusion: Concurrently, cerebral blood flow drops by up to 50%. This creates a critical mismatch between cellular metabolic demand and vascular energy supply.
4. Mitochondrial Dysfunction: Intracellular calcium sequestration impairs oxidative phosphorylation, leaving neurons highly vulnerable to secondary injury for 7 to 14 days.

Diagnosis & Clinical Assessment

Diagnosis is clinical and relies on recognizing symptoms across four clinical domains:

• Somatic: Headache (most common, >80%), dizziness, nausea, photophobia, phonophobia, balance difficulty.
• Cognitive: Feeling "in a fog," slowed processing speed, difficulty concentrating, memory impairment.
• Affective / Emotional: Irritability, sadness, emotional lability, anxiety.
• Sleep: Drowsiness, insomnia, sleeping more or less than usual.

Sideline Tools: The Sport Concussion Assessment Tool 6 (SCAT-6) or Standardized Assessment of Concussion (SAC) evaluates orientation, immediate memory, concentration (digits backward, months in reverse), and balance via the Modified Balance Error Scoring System (mBESS).

Amsterdam 2023 / Berlin Consensus Guidelines: The Shift to Active Recovery

Historical practice enforced strict, prolonged sensory deprivation in a dark room until all symptoms completely resolved ("cocoon therapy"). Landmark clinical trials and the 6th International Consensus Conference on Concussion in Sport (Amsterdam 2023) have proven that prolonged rest is harmful, predisposing patients to deconditioning, social isolation, depression, and persistent symptoms.

• The Modern Paradigm:
  • Initial 24 to 48 Hours: Relative physical and cognitive rest (limiting screens, avoiding intense physical exertion).
  • After 48 Hours: Early, gradual resumption of light physical activity (e.g., brisk walking, stationary cycling) that does not bring on or worsen symptoms, even if the patient is not yet fully asymptomatic. Sub-symptom aerobic exercise accelerates autonomic recovery and shortens time to full clinical resolution.

The 6-Stage Graduated Return-to-Sport (RTS) Strategy

Athletes must never return to contact sport on the day of injury ("when in doubt, sit them out"). Progression through the following 6-stage protocol begins once the initial 24–48 hours of rest are complete:

               GRADUATED 6-STAGE RETURN-TO-SPORT (RTS) PROTOCOL
               
    ┌────────────────────────────────────────────────────────────────────────┐
    │ Stage 1: Symptom-Limited Activity                                      │
    │ • Daily activities that do not provoke symptoms (walking, light tasks) │
    │ • Goal: Gradual reintroduction of work/school activities               │
    └───────────────────────────────────┬────────────────────────────────────┘
                                        │ (≥24 hours without symptom exacerbation)
                                        ▼
    ┌────────────────────────────────────────────────────────────────────────┐
    │ Stage 2: Light Aerobic Exercise                                        │
    │ • Walking or stationary cycling at slow-to-medium pace (<70% HRmax)    │
    │ • NO resistance training; NO head impact activities                    │
    │ • Goal: Increase heart rate without provoking symptoms                 │
    └───────────────────────────────────┬────────────────────────────────────┘
                                        │ (≥24 hours without symptom exacerbation)
                                        ▼
    ┌────────────────────────────────────────────────────────────────────────┐
    │ Stage 3: Sport-Specific Exercise                                       │
    │ • Running drills in soccer, skating drills in hockey                   │
    │ • NO head impact activities; NO contact                                │
    │ • Goal: Add movement and dynamic coordination                          │
    └───────────────────────────────────┬────────────────────────────────────┘
                                        │ (≥24 hours without symptom exacerbation)
                                        ▼
    ┌────────────────────────────────────────────────────────────────────────┐
    │ Stage 4: Non-Contact Training Drills                                   │
    │ • Harder training drills (passing, agility); progressive resistance    │
    │ • Goal: Exercise, coordination, and increased cognitive load           │
    └───────────────────────────────────┬────────────────────────────────────┘
                                        │ (≥24 hours without symptom exacerbation)
                                        ▼
    ┌────────────────────────────────────────────────────────────────────────┐
    │ Stage 5: Full-Contact Practice                                         │
    │ • MANDATORY: Prior formal medical clearance from licensed clinician    │
    │ • Normal training activities, live scrimmages, checking                │
    │ • Goal: Restore confidence and assess functional skills by coaching    │
    └───────────────────────────────────┬────────────────────────────────────┘
                                        │ (≥24 hours without symptom exacerbation)
                                        ▼
    ┌────────────────────────────────────────────────────────────────────────┐
    │ Stage 6: Return to Sport                                               │
    │ • Unrestricted competition, normal game play                           │
    └────────────────────────────────────────────────────────────────────────┘

• Progression Rule: Each stage requires a minimum of 24 hours. If any concussive symptoms recur during or after a stage, the athlete must stop activity, rest for 24 hours until asymptomatic, and then drop back to the previously tolerated asymptomatic stage.
• Return-to-Learn (RTL): Cognitive recovery must precede full return to sport. Accommodations include partial school days, frequent rest breaks, extended time for assignments, and postponement of standardized testing.

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Second Impact Syndrome & Persistent Post-Concussive Symptoms

Second Impact Syndrome (SIS)

Second Impact Syndrome is a catastrophic complication that occurs when an athlete sustains a second head impact before symptoms from an initial concussion have completely resolved (typically within days to weeks).

• Pathophysiology: During the post-concussive vulnerable window, cellular autoregulation of cerebral blood flow is disrupted. A second impact—even minor, such as a routine tackle or blow to the chest that transmits rotational force to the head—triggers sudden, irreversible loss of cerebrovascular autoregulation. This causes massive cerebral engorgement, severe diffuse brain edema, intracranial hypertension, and fatal brainstem herniation within 2 to 5 minutes.
• Prognosis: Mortality approaches 50%, and permanent catastrophic neurological disability occurs in nearly 100% of survivors. It occurs predominantly in children, adolescents, and young adults under age 25.
• Prevention: Absolute adherence to concussion return-to-play protocols and medical clearance.

Persistent Post-Concussive Symptoms (PPCS)

Historically termed "post-concussion syndrome," PPCS is defined as concussion-related symptoms persisting beyond expected recovery windows (>4 weeks in adults, >12 weeks in children). Management requires targeted multidimensional active rehabilitation:

• Vestibular and ocular physical therapy (for vestibulo-ocular reflex [VOR] dysfunction and convergence insufficiency);
• Cervical spine manual therapy (for cervicogenic headache and neck spasm);
• Sub-symptom-threshold aerobic exercise prescription;
• Cognitive Behavioral Therapy (CBT) and sleep hygiene for associated affective disturbances.