Comprehensive Study Notes on Head Trauma and Traumatic Brain Injury

Prehospital Emergency Care: Head Trauma

Anatomy of the Skull and Brain

The Skull
- The cranial skull is a rigid vault that surrounds and protects the brain.
- The human face is composed of $14$ distinct bones.
- The basilar skull (the floor of the cranium) is recognized as its weakest portion.
- The basilar skull bones are significantly thin and feature extensive perforations to accommodate the spinal cord, nerves, and blood vessels.
- Key bones of the skull include:
  - Parietal bone
  - Frontal bone
  - Sphenoid bone
  - Temporal bone
  - Ethmoid bone
  - Lacrimal bone
  - Maxilla
  - Nasal bone (including middle and inferior nasal concha)
  - Mandible
  - Occipital bone
  - Mastoid process
Protective Systems and Fluids
- Cerebrospinal Fluid (CSF): The brain is cushioned by CSF. The leakage of CSF from the nose or ears is a clinical Hallmark indicating a basilar skull fracture.
- The Meninges: Three distinct layers of tissue surround the brain:
  - Dura Mater: The outermost, toughest layer.
  - Arachnoid: The middle, web-like layer.
  - Pia Mater: The innermost layer in direct contact with the brain surface.
Anatomical Spaces and Bleeding
- Epidural: Bleeding that occurs in the potential space between the dura mater and the internal surface of the skull.
- Subdural: Bleeding that occurs beneath the dura mater, typically resulting from venous injury.
- Subarachnoid Hemorrhage: Bleeding that occurs between the arachnoid membrane and the surface of the brain (the pia mater).
Brain Structures and Functions
- Cerebrum: Divided into two hemispheres, each containing four lobes. It is responsible for conscious thought, sensory functions, emotion, and personality.
- Cerebellum: Coordinates muscular movements and reflexes to maintain posture and equilibrium.
- Brainstem: Comprised of the pons, midbrain, and medulla oblongata. It serves as the control center for automatic functions including cardiac, respiratory, and vasomotor systems. The medulla serves as the physical connection between the brain and the spinal cord.

Pathophysiology of Head and Brain Injury

Scalp Injuries
- These are classified as soft tissue injuries.
- Because the blood vessels in the scalp do not constrict well, bleeding can be profuse.
- Bleeding beneath the scalp can create swelling (hematomas) that makes the assessment of underlying skull integrity difficult.
Skull Injuries
- A deformity in the skull requires extreme trauma.
- Linear Skull Fracture: The most common type of skull fracture.
- Depressed Skull Fracture: Occurs when bone ends are pushed inward toward the brain tissue.
- Open vs. Closed: Fractures are classified based on the integrity of the overlying scalp.
- Basilar Skull Fracture: Involves the floor of the cranium and often results in characteristic leakage of CSF.
Traumatic Brain Injury (TBI)
- TBI is brain injury caused by trauma, which can result from blunt force, penetrating trauma, or secondary complications.
- Increasing pressure within the skull (Intracranial Pressure or ICP) due to swelling or bleeding decreases brain tissue perfusion.
Primary vs. Secondary Brain Injury
- Primary Brain Injury: The immediate result of trauma at the time of insult, caused by direct impact, acceleration/deceleration forces, or penetrating wounds.
- Secondary Brain Injury: The worsening of the initial injury caused by physiological factors that must be managed by the EMT:
  - Hypoxemia
  - Hypercarbia
  - Hypoglycemia
  - Hyperglycemia
  - Hyperthermia
  - Hypotension (defined as a systolic blood pressure < $90\,mmHg$ )
Management Goals to Minimize Secondary Injury
- Maintain a patent airway.
- Ensure adequate ventilation.
- Maintain a systolic blood pressure > $90\,mmHg$ .
- Maintain normal body temperature.
- Maintain normal blood glucose levels.
- Stop seizures as quickly as possible (often requiring ALS intervention).
Brain Herniation
- Increased ICP from bleeding or swelling forces brain tissue out of its normal position and through the foramen magnum (or against other rigid structures).
- This compression obliterates vital brainstem functions.
- Signs/Symptoms of Herniation:
  - Dilated or sluggish pupil on one side.
  - Weakness or paralysis.
  - Severe alteration in consciousness.
  - Abnormal posturing (Decorticate or Decerebrate).
  - Abnormal breathing patterns.
  - Cushing Reflex: Increased systolic blood pressure and decreased heart rate.

Specific Types of Brain Injuries

Diffuse Axonal Injury (DAI)
- Caused by shearing, tearing, and stretching of nerve fibers.
- Related to severe acceleration and deceleration forces; interferes with nerve impulse transmission.
- Categories: Mild (Concussion), Moderate, or Severe.
Concussion
- A mild form of DAI.
- Presentation: Momentary confusion to brief loss of responsiveness, followed by a headache.
- Effects appear immediately and typically improve gradually.
Contusion
- Physical bruising and swelling of the brain tissue.
- Can occur alongside a concussion; results from coup/contrecoup or acceleration/deceleration mechanisms.
Hematomas
- Subdural Hematoma: Collection of blood between the dura mater and arachnoid, resulting from damage to bridging veins.
  - Acute: Signs and symptoms appear immediately.
  - Occult: Signs and symptoms are delayed for days or weeks.
  - High Risk: Elderly patients, those on anticoagulants/antiplatelets, and alcoholics.
- Epidural Hematoma: Rare but extremely emergent; often associated with temporal skull fractures and damage to the middle meningeal artery. Bleeding is rapid and severe.
  - Late Signs: Fixed/dilated pupils, absent reflexes, and rapidly decreasing vital signs.
Subarachnoid Hemorrhage (SAH)
- Bleeding beneath the arachnoid membrane and above the pia mater.
- Commonly caused by blunt force trauma leading to a ruptured vessel.
- Symptoms: "Worst" headache of their life, nausea/vomiting, photophobia, dizziness, and neck stiffness.
- Ocular Sign: The affected eye may look downward and outward, and the patient may be unable to lift the eyelid.

Assessment-Based Approach

Scene Size-Up
- Mechanisms of injury: MVCs, falls, assaults, sports, and recreation.
- Look for clues like a fractured windshield.
- Never assume mental status changes are due to intoxication; always assume head injury until proven otherwise.
Primary Assessment
- Manual in-line stabilization of the spine is the first priority.
- Airway: Use the jaw-thrust maneuver. Facial injuries (e.g., mandible fractures) can cause airway blockage.
- Oxygenation: Maintain $SpO_2 \ge 95\%$ . Provide positive pressure ventilation (PPV) for inadequate breathing.
Glasgow Coma Scale (GCS)
- Eye Opening: Spontaneous ( $4$ ), To sound ( $3$ ), To pressure ( $2$ ), None ( $1$ ).
- Verbal Response: Oriented ( $5$ ), Confused ( $4$ ), Words ( $3$ ), Sounds ( $2$ ), None ( $1$ ).
- Motor Response: Obeys commands ( $6$ ), Localizing ( $5$ ), Normal flexion ( $4$ ), Abnormal flexion/Decorticate ( $3$ ), Extension/Decerebrate ( $2$ ), None ( $1$ ).
Secondary Assessment and Vital Signs
- Frequency: Vital signs must be recorded every $5\,minutes$ .
- Blood Pressure: High SBP indicates rising ICP; Low BP indicates bleeding elsewhere in the body.
- Pulse: Decreased heart rate indicates rising ICP or severe hypoxia; increased rate indicates shock from other bleeding.
- Amnesia:
  - Retrograde: Unable to remember events leading up to the incident.
  - Anterograde: Unable to remember events after the incident.
- Hyperventilation Protocol: Consider at a rate of $20/min$ only if signs of herniation are present (e.g., fixed/unequal pupils, GCS drop of $\\ge 2$ points, Cushing reflex, hemiplegia).

Emergency Medical Care and Special Populations

General Care Guidelines
- Standard Precautions.
- Maintain spine motion restriction.
- Control bleeding: Do NOT apply pressure to open/depressed skull injuries. Do NOT stop the flow of CSF/blood from ears or nose.
- Be prepared for seizures and monitor for deterioration.
Pediatric Head Trauma
- Anatomic Variations: Larger/heavier heads, higher water content in the brain, less myelinated sheaths.
- Signs of ICP in Infants: Bulging fontanel, irritability, vomiting, and the "setting sun" sign (pupils appear low in the eye).
- Impact Seizures: Seizures immediately after trauma. If occurring > $20\,minutes$ post-trauma, it likely indicates brain injury.
- Shaken Baby Syndrome: Results from forceful, repeated shaking. Risk factors include young/stressed parents and domestic violence. Symptoms include irritability, poor feeding, respiratory distress, and recurrent vomiting.
Geriatric Head Trauma
- Older patients have higher mortality rates.
- Smaller brain size allows for more movement within the skull.
- Medications (anticoagulants/antiplatelets) significantly increase bleeding risks.

Questions & Discussion

Case Study Question: What are the first steps the EMTs must take?
- Response: Matt must immediately perform in-line spinal stabilization and use the jaw-thrust maneuver to open the airway while Luis prepares for suctioning.
Case Study Question: What findings lead the EMTs to suspect traumatic brain injury?
- Response: Unresponsiveness, facial bleeding, deep and rapid breathing, a heart rate of $60\,bpm$ (relative bradycardia for trauma), and nonpurposeful movement to pain.
Discussion on Posturing:
- Flexion (Decorticate): Indicated by nonpurposeful drawing in of the arms toward the core.
- Extension (Decerebrate): Indicated by straightening and extending the extremities.

Case Study: Motorcycle Collision

Initial Scene: EMTs Matt Brooks and Luis Garcia respond to a male in his $30s$ ejected from a motorcycle after striking a car. The patient was unhelmeted.
Findings: The patient is unresponsive with facial bleeding and a hematoma on the frontal area. Respirations are deep and rapid. Radial pulse is strong at $60\,bpm$ . He shows nonpurposeful movement to painful stimuli.
Outcomes: The patient was found to have a subdural hematoma and high ICP. He was intubated and underwent surgery to relieve pressure. Despite appropriate care, the prognosis remained poor due to the severity of the TBI.