Traumatic Brain Injuries

Pathophysiology

The mechanism of injury (MOI) is a direct blow to the patient’s head or a direct blow to another part of their body where the force is transmitted to their brain via their spinal column, cord, and associated soft tissue (aka: whiplash). The brain essentially floats inside the skull in cerebral spinal fluid (CFS). The fluid acts to protect and cushion sensitive brain tissue from minor impacts in much the same way as egg white protects the yolk. If the force generated by the traumatic event is strong enough, the brain will bounce off inside of the skull damaging sensitive brain tissue (as shown in the illustrations below).

A concussive injury, should it occur, can be functional or structural. A person with a functional concussive injury will present or develop S/Sx, typically within two hours; however, standard imaging techniques (CT, MRI) show no structural damage. The S/Sx of a functional injury—see the chart below—are likely caused by axional stretching and disruption of ion channels, follow a predefined progression, and usually resolve on their own within 7-10 days; although, in some cases, S/Sx may persist for months. That said, structural damage is possible and may lead to increased intracranial pressure (ICP) and potentially death in rare cases. The concern from a field perspective is whether a person with an apparent positive MOI can remain in the field or requires an evacuation. And, if an evacuation is necessary: What is its urgency?

Emergency department physicians typically rely on one of seven clinical algorithms to decide if a patient requires imaging or not (Click here to read an article that discusses the pros and cons of each rule), only the High Risk Criteria for the Canadian CT Head Injury Rule and the NEXUS II can be easily extrapolated to aid evacuation decisions in the field; both may be used in the presence of a significant mechanism of injury. It's important to remember that the guidelines are conservative and few concussed patients go on to develop increased ICP.

Assessment

All people with a positive mechanism must be evaluated for a potential traumatic brain injury (TBI). TBIs can be grossly subdivided into concussion and increased ICP. Concussions can be further subdivided into mild, moderate, and severe, while increased ICP can be broken down into early and late. After a traumatic MOI a patient may present with any of the problems discussed below and progress, or not, from that point. Note that the problems are mutually exclusive and a patient may only have one problem—concussion or increased ICP—at any given time. Seizures are possible at any point especially in infants and young children and common in unresponsive patients with late increased ICP prior to posturing.

Patient's with serious head injuries typically have obvious soft tissue damage to their head including:

• Clear or light yellow cerebral spinal fluid (CFS) leaking from the patient's nose or ears; the CFS may be blood-tinged or accompanied by blood.
• A depressed skull fracture, scalp hematomas (that make assessing the underlying integrity of the skull difficult) or penetrating trauma.
  

• Bruising around both eyes (racoon eyes) and/or behind and below the ears (Battle's sign, caused by a fracture of the temporal bone) indicates a basal skull fracture. Both present hours or days later; bruising that presents immediately after the traumatic event is typically the result of direct trauma.
  

Mild Concussion

• Positive mechanism.
  
• Awake with no loss of consciousness (LOC) or amnesia.
• S/Sx of a concussion (refer to table) are present two hours after the traumatic event.
• While the mildly concussed patient is in no danger of developing increased ICP, they may take days, weeks, or months to fully heal. During this time they will require both mental and physical rest.
• Assess & Treat children < 16-years-old, adults > than 65-years-old, patients with a bleeding disorder, and those taking blood thinners as per moderate concussion; they are candidates for structural damage even if they present with no LOC and no amnesia.

Moderate Concussion

• Positive mechanism.
  
• Awake after a temporary loss of consciousness.
  
• Amnesia. Patient will NOT remember details of the event, may exhibit short-term memory loss, or may have forgotten a portion of time leading up to the event. Some memories may return with time.
• Patient presents with S/Sx of a concussion: headache, dizziness, ataxia, vision problems, concentration problems, emotional problems, and/or sleep-related problems, etc. (See table.) S/Sx tend to slowly get better over the next 24 hours, they should not worsen.
• Patient may present with scalp hematoma or CSF leaking from nose or ears.
• May initially be nauseous 2º to parasympathetic ASR.
• Anticipated problem is a severe concussion.

Severe Concussion

The distinction between a moderate and severe concussion is important as the mechanism MAY have been severe enough to structurally injure brain cells or small blood vessels, cause intracranial leaks and swelling, and lead to increased ICP. Worsening S/Sx over the next 24 hours indicate a more severe injury (severe concussion) and can be difficult to recognize if the patient is not closely monitored.

Pay close attention to the patient’s overall function: Are their S/Sx severe enough that they interfere with their daily function (severe concussion)? When doubt, choose the worst reasonable case scenario.

• Positive mechanism.
• Awake after a temporary loss of consciousness.
• Amnesia. Patient will NOT remember details of the event, may exhibit short-term memory loss, or may have forgotten a portion of time leading up to the event. Some memories may return with time.
  
• Patient presents with S/Sx of a concussion: headache, dizziness, ataxia, vision problems, concentration problems, emotional problems, and/or sleep-related problems, etc. (See table.) S/Sx worsen over the next 24 hours.
• Patient may present with a depressed skull fracture, scalp hematoma, penetrating trauma, and/or CSF leaking from nose or ears.
• Anticipated problem is increased ICP.
  

Early Increased ICP

• Awake after a temporary loss of consciousness or amnesia.
• S/Sx of a severe concussion plus persistent vomiting. Most patients complain of a severe migraine-like headache and may become combative. The initial episode of vomiting may be explosive, projectile, and appear suddenly without warning; subsequent episodes are less violent as the patient's AVPU decreases.
  
• ± Depressed skull fracture, scalp hematoma, penetrating trauma, or CSF leaking from nose or ears
  

Late Increased ICP

• Voice-responsive, pain-responsive, or unresponsive.
• ± Depressed skull fracture, scalp hematoma, penetrating trauma, or CSF leaking from nose or ears
  
• Vomiting continues and eventually stops as the brain stem is compressed.
  
• Decreasing pulse, increasing BP, irregular respirations
  
• Seizures are common in unresponsive patients prior to posturing.
• Decerebrate posturing indicates brain stem herniation and is typically  accompanied by a changing respiratory rate, and subsequent respiratory and cardiac arrest; it is often preceded by decordicate posturing.

Treatment

Mild Concussion

• Rule out a possible spine injury.
  
• Acetaminophen for headache pain.
• Begin a Level 3 evacuation. Sleep and rest are required for healing. Minimize physical and mental exertion during the evacuation until S/Sx resolve.

Moderate Concussion

• Rule out a possible spine injury.
• Acetaminophen for headache pain.
• Begin a Level 3 EVAC; minimize physical & mental exertion. If sleeping, wake every 2-4 hours as necessary to evaluate.
• Closely monitor patient for worsening S/Sx. If S/Sx appear to interfere with the patient’s daily function, upgrade to a severe concussion.
  

Severe Concussion

• Rule out a possible spine injury.
  
• Begin a Level 2 evacuation; the patient may be developing increased ICP or a subdural hematoma.
• Monitor for persistent vomiting (early increased ICP) for 24 hours. As with other concussions, sleep and rest are required for healing. As much as reasonably possible, minimize physical and mental exertion during the evacuation. If sleeping, wake every 2-4 hours to evaluate.
  

Early Increased ICP

• Rule out a possible spine injury; patient may not be able to self-evacuate.
  
• Begin a Level 1 evacuation.
• Package litter patients on their side; maintain and protect their airway.
  

Late Increased ICP

• Begin a Level 1 evacuation; patient may die during the evacuation.
• Maintain and protect the patient's airway.
• Package litter patients on their side.
• Consider rescue breathing if the patient's respiratory rate is slow or absent; decerebrate posturing means irreversible damage to the patient's brain stem. Cardiac arrest = Death; CPR is not indicated.
  

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