Objectives:

1. Understand the different anatomic types of cranial trauma, their radiologic appearance on CT, and their common clinical presentations.

2. Understand how to assess a victim of traumatic brain injury, determine level of consciousness and signs of herniation.

3. Describe how to initially stabilize trauma patients with severe head injury and provide empiric treatment for elevated incranial pressure. Describe how to work up patient with suspected head trauma.

4. Describe the clinical and radiologic features of chronic subdural hematoma.

5. Understand the role of ischemia and spreading depolarization in the pathophysiology of head trauma, and how this may be treated clinically.

1. Overview of head trauma

1. Epidemiology

Epidemic in US
2,000,000 medically attended cases/year
400,000 hospitalizations/year
75,000 deaths/year
Major cause of permanent disability
Leading cause of death in 15-40 year old age group
Changing ratio of blunt vs. penetrating injury
Importance of prevention

2. Characterization

1. Clinical grading
     Mild - GCS 13-15
           Patient typically mildly lethargic, disoriented
     Moderate - GCS 9-12
           Patient typically sleepy or obtunded, able to follow commands with arousal.
           Confused.
      Severe - GCS 3-8
           Patient comatose, unable to follow commands or perform purposeful motor activity.
           Range of motor activity: localizes, withdraws, decorticate posturing, decerebrate
           posturing, nil.

Review Glasgow Coma Scale (see notes on Intracranial hemorrhage lecture)

               B.   Anatomic features (general)
                         Blunt vs. Penetrating
                         Closed vs. Open
                         Focal (contusion or hemorrhage) vs. Diffuse
                              Focal lesions produce dysfunction specific to the injured area of the brain
                              Diffuse injuries are associated with global dysfunction, eg. loss of consciousness,
                              cognitive and memory problems
                         Hemorrhagic vs. Non-hemorrhagic

3. Pathophysiology

1. Primary tissue injury
      Tissue injury due to trauma mechanism, eg contusion, tissue shearing
   
2. Secondary injury
       Tissue damage which builds over minutes-hours after primary injury
       Role is becoming increasingly recognized
       Major target for investigative research and potential clinical intervention
   Sources of secondary injury
        Ischemia (cerebral perfusion is compromised by systemic hypotension or by elevated
             intracranial pressure).
                      CPP=MAP-ICP
         Excitotoxicity
                       Tissue injury and ischemia causes release of glutamate, aspartate & potassium
                       and intraneuronal accumulation of calcium. Result is wave of spreading
                       depolarization, hypermetabolism and worsening tissue ischemia.
   Mainstay of therapy is to optimize cerebral perfusion. Newer therapies utilize hypothermia to decrease tissue metabolism, glutamate or calcium antagonists.

IV. Management of traumatic brain injury

 A.   Prehospital care
             ABC's (Airway, breathing, circulation)
             Fluid resuscitation to reverse shock, hypotension
             Spine precautions
             5-10% of head trauma patients have unstable spine injury
             An effective EMS and air ambulance system can dramatically reduce mortality from
                     head trauma

B.   Initial evaluation and resuscitation
             Rapid neurological examination (1-3 minutes)
                    Assess GCS, pupil function, doll’s eyes, cough, gag, corneal reflex
             Empiric management of elevated ICP
                    See intracranial hemorrhage lecture notes
                    Intubaton, ventilation, sedation, mannitol, head elevation
             Secondary injury survey
                    Examine head, ears, eyes, nasopharynx, mouth for injury, facial fractures
                    C-spine xrays
                    Evaluate for peripheral injury
             STAT head CT scan
                    Diagnostic procedure of choice for all patients with suspected traumatic brain
                              injury
             Repeat neurologic exam frequently

C. Definitive management of traumatic brain injury
            Immediate surgery for evacuation of hematoma, if necessary
            Monitor ICP with implanted pressure gauge
            Medically manage cerebral edema to maintain cerebral perfusion pressure > 70 mmHg
            Perform serial head CT scans
                     20% of cerebral contusions may enlarge to surgical hematoma

D. Questions regarding traumatic brain injury
           1. Can patients recover from deep coma and severe injury?
           2. Can we predict who will and who will not make a good recovery?
           3. What are favorable and unfavorable prognostic factors?
           4. What is brain death and is it a legal means of declaring death?

V. Specific types of head injury

A. Concussion
            Brief loss of consciousness with normal head CT scan, normal neuro exam
            Patient may have mild lethargy and/or confusion
            Treatment: observation
            In sports, avoid any risk of reinjury until any sxs have completely resolved.
                   Second impact before full recovery may be fatal.

B. Skull fracture
           May or may not have associated underlying brain injury
           Linear or non-depressed - observe
           Open or compound - irrigate, close, antibiotic coverage
           Depressed - require surgical repair
                  Any associated dural tear or brain laceration requires surgical repair
            Basilar skull fracture - fracture around orbital roof, sphenoid bone, or petrous or mastoid
                        portion of temporal bone.
                   Battle’s or Racoon’s eye signs
                   May be associated with injury to cranial nerves 2, 7 or 8, or CSF leak into nose (rhinorhea)
                   or ear (otorhea)- these require special attention
                   Seldom life threatening

C. Cerebral contusion / intracerebral hematoma
             Area of focal tissue injury. Neurological deficit depends on area injured.
             Commonly occur in coupe/contra coupe pattern
                         eg. frontal / occipital
             20% of contusions may expand into surgical hematoma
             Observe patients in ICU, repeat head CT scan within 24 hours.

D. Epidural Hematoma - EDH
              Lens shaped hematoma between dura and skull.
              Associated with skull fracture and laceration of dural artery (eg. middle meningeal artery).
              Underlying brain is usually not injured
              Arterialized bleeding results in rapid expansion of hematoma and neurological decline
              Often presents with brief loss consciousness, followed by lucid interval of minutes to hours,
                    before rapid neurological decline into coma.
               Extreme neurosurgical emergency. Timely diagnosis and surgery is often followed by excellent
                     recovery.

E. Subdural hematoma - SDH
                Crescent shaped hematoma lying between brain and dura, conforming to brain surface.
                 Indicative of high acceleration/deceleration injury with tearing of bridging veins or cortical
                        arterioles.
                 Usually associated with severe diffuse injury, immediate deep coma from moment of impact.
                 Extreme neurosurgical emergency.
                 30% mortality, 30% good outcome.

F. DAI - diffuse axonal injury
                 Also known as shear injury or brain stem contusion
                 High acceleration/deceleration injury with shock waves and momentary tissue distortion
                         causing microscopic tearing of nerve fibers.
                  Radiographically consists of small petechial hemorrhages in white matter tracts.
                  Causes immediate deep coma.
                  Often associated with severe cerebral edema and ICP elevation.
                  Mortality is 30-40 %, good outcome 20-30 %.

G. Gunshot wound - GSW
                  Causes mixtures of skull fracture, DAI, intracerebral hemorrhage, epidural and subdural
                         hematomas, in addition to direct tissue injury. May also cause injury to major cerebral
                         vessels.
                   High velocity weapons cause extreme diffuse injury from tissue cavitation.

H. Chronic subdural hematoma
                   Usually found in older patients with cerebral atrophy.
                   Minor trauma causes small, often minimally symptomatic subdural hemorrhage. As clot
                           liquifies over next 1-3 weeks, the hemorrhage may expand into a significant mass.
                           Hematoma resembles dark liquid crankcase oil.
                    CT appearance, hypodense crescent shaped mass between dura and brain.
                     Presenting symptoms: elevated ICP often associated with hemiparesis. May also cause
                            TIA-like episodes or seizures.
                     Treatment consists of surgical drainage of hematoma via burr holes and irritation. Most
                             patients make excellent recovery.