Clinical Practice Guideline

for

HEAD INJURY

Developed for the

Aerospace Medical Association

by their constituent organization

American Society of Aerospace Medicine Specialists

 

Overview: Some element of head injury occurs in over 70% of individuals involved in automobile accidents and in at least 50% of all major trauma excluding burns.  An estimated 80 to 90% of persons with head injury have mild trauma.  Of those persons discharged with a good recovery from mild to moderate head injuries, about 10% have a continuing need for medical care services as a result of their head injury.  The estimated prevalence in the US is 500,000 hospitalizations and 75,000 deaths per year.  Closed head injury is the most common, most often related to rapid deceleration of the head (with or without impact).  A combination of neurologic, cognitive, behavioral, and psychosocial variables are involved in the outcome of head injury, and the latter two variables are probably the most important.  Males are affected three times as often as females and the predominant age group is 15-24.

 

The term "head injury" is a poor term that does not indicate the actual injury or risk of further problems.  Head injury can be divided into the following categories:

 

Mild Head Injury: Injury without loss of consciousness, amnesia, or abnormality on examination, or head injury where unconsciousness has been less than 30 minutes and amnesia less than one hour.

 

Moderate Head Injury: Patients with a normal MRI or CT scan obtained within two days of injury and one or more of the following: unconsciousness of more than 30 minutes but less than 24 hours, amnesia of more than one hour but less than 24 hours, or a small epidural collection of blood found only on CT scan or MRI, without any evidence of parenchymal injury and followed to resolution without surgery.

 

Severe Head Injury: Head injury associated with one or more of the following: unconsciousness or amnesia or a combination of the two exceeding 24 hours duration, radiological evidence of retained metallic or bony fragments, leptomeningeal cyst, aerocele or arteriovenous fistula, depressed skull fracture with or without dural penetration, traumatic or surgical laceration or contusion of the dura mater or the brain or a history of penetrating brain injury, focal neurological signs, epidural, subdural, subarachnoid or intracerebral hematoma, CNS infection such as meningitis or abscess within six months of head injury, or CSF rhinorrhea or otorrhea lasting more than 7 days.  It also includes head injury associated with one or more of the following: post-traumatic seizures, significant neurological deficits indicative of CNS parenchymal injury, evidence of impairment of higher CNS functions or personality, or CSF shunt.

 

Aeromedical Concerns: Closed head injury is the most frequently encountered type of head injury in flyers.  The decision to return an aviator to the cockpit must be based on the probability of developing serious sequelae.  The duration of unconsciousness is considered an important predictive factor for post-traumatic epilepsy.  It has been reported that if the duration of unconsciousness exceeds 24 hours there is a 36% seizure incidence rate.  To assess risk of residual brain damage from closed head trauma, the symptom of most value is the duration of post-traumatic amnesia (PTA), which is the interval from the moment of injury to the recovery of sequential memory.  The duration of unconsciousness and of retrograde amnesia have proven to be of less use, and more difficult to ascertain.  Where the PTA is more than 24 hours, not only is the individual at greater risk of more severe brain damage, but the risk of traumatic epilepsy is increased.  The overall risk of traumatic epilepsy after closed head injury is 1-5%.  With the duration of PTA more than 24 hours the risk is 4%.  If a seizure occurs within the first week post injury the risk of further seizures is 25%.  With an intracranial hematoma, or with cerebral hemorrhage the risk of epilepsy rises to 35%.  When seizures do occur, 50% occur within the first 6 months, 75% at 12 months, and 90% at 2 years. The risk of traumatic epilepsy is substantially reduced if 2 years have elapsed after the head injury but in 25% traumatic epilepsy develops many years after the injury.  If an aircrew member had been taking a prophylactic anticonvulsant, he would be ineligible to fly until it had been withdrawn and he had been seizure free for at least 6 months.

 

The parts of the brain most vulnerable to damage are the frontal and temporal lobes.  The cognitive tasks of judgment, memory, higher abstract reasoning, and mental flexibility are largely mediated by these parts of the brain.  Mild intellectual deficits may be missed on a detailed neurological exam, and a good neuropsychological assessment combined with reports from perceptive relatives or friends may be the best tools for detection.

 

Medical Work-up: Acute management for head injury is in accordance with published ATLS protocol.

 

Aeromedical Disposition (military): Grounding and waiver criteria vary depending on the category of head injury under consideration and on the branch of service.  Generally the following procedures are recommended:

 

Mild Head Injury. If there is no loss of consciousness and the physician neurological examination is normal, it is suitable to return to flying duties without a wait.  If there was mild loss of consciousness or amnesia, the aviator needs a complete neurological examination by his or her physician, and at a minimum, neuropsychological screening within 30 days.  If this screening is normal, the aviator may return to flying duties after a 30-day observation period.  If abnormal, a local neurologic evaluation is required, to include an EEG and MRI.  If these are normal a waiver for flying may be considered, but if abnormal an extensive neurological evaluation will be necessary.  A history of seizure within five minutes of the injury (without recurrence) may be considered for waiver after a complete neurological evaluation.

 

Moderate Head Injury. Requires complete neurological evaluation by an internist or neurologist, CT scan within 48 hours and a routine MRI, EEGs (routine and sleep deprived), and an acceptable neuropsychological evaluation (Aviation Cognition Screen, MMPI, Halstead-Reitan, and WAIS-R).  Examinees may be considered for return to aviation duties after six months if an early CT done within 48 hours was normal.  Otherwise, the patient is considered for return to aviation duties in two years.

 

Severe Head Injury. Requires complete neurologic evaluation by a neurologist or internist, an early CT or MRI, and neuropsychological evaluation (tests as in moderate head injury).  If the evaluations are normal, then a complete neurological evaluation is required which will also include a neuropsychological consultation (to include neuropsychological testing), and an EEG (routine and sleep deprived) and an MRI.  Examinees may be considered for return to aviation duties after five years if all of the exams are normal.  For individuals with post-traumatic seizures, significant neurological deficits, evidence of impairment of higher CNS functions, or a CSF shunt, a return to flying status is not recommended.

 

Aeromedical Disposition (civilian): In civil aviation in the United States closed head injury is also evaluated based on the time of unconsciousness and post traumatic amnesia.  The definition of severe head injury is loss of consciousness (LOC) or alteration of consciousness (AOC) greater than 24 hours, brain contusion or hemorrhage, inability to follow commands and motor responses that vary to stimuli.  Post traumatic amnesia (PTA) is usually from one to seven days.  Very Severe Head Injury is also a classification that is used.  The definition of very severe is eyes are closed, lack of response to deep pain, inability to follow commands, and no motor movement or posturing response. PTA is generally longer than seven days. 

 

Applicants with mild or moderate head injury and a seizure within the first week must have at least a two-year recovery off medications.  If a seizure occurs beyond the first week or the airman suffered a severe head injury, the airman should be five years seizure free off medications prior to any consideration.  If the airman had an intracerebral hemorrhage or brain contusion even though there have been no seizures, they are not considered for medical certification for five years.  This is due to the increased likelihood of seizures in such circumstances.   

 

Waiver Experience (military): There are currently 407 rated aviators in a military waiver file with the diagnosis of head injury.  Of these, 44 were disqualified from flying duties.  The majority of those disqualified were in the moderate and severe categories. 

 

Waiver Experience (civilian): Return to aviation duties in the civilian community will be similar, but will be dependent on the type of rating the pilot has.  As of the present writing there are no specific pathology codes for closed head injury. 

 

References:

 

Cooper PR (ed): Head Injury, Third Edition. Los Angeles, Williams and Wilkins. 1993.

 

Dambro MR, Griffith JA. Griffith’s 5 Minute Consult, Philadelphia, Williams and Wilkins. 1996; 134-5.

 

DeHart RL (ed): Fundamentals of Aerospace Medicine, 2nd edition, Baltimore, Williams & Wilkins, 1996: 635-37, 878-82.

 

Ernsting J, King P. Aviation Medicine, 2nd Edition, Boston, Butterworths and Co, Ltd. 1988; 645-7.

LeBlanc KE. Concussions in sports: Guidelines for return to competition, American Family Physician, 15 Sep 1994:50(4); 801-8.

 

Lyons TJ, Katchen MS. An aviator with head trauma and posttraumatic amnesia, Aviation Space Environ Med, Oct 1989:1016-7.

 

McLaurin RL (ed): Head Injuries--Second Symposium on Neural Trauma. New York, NY, Grune and Stratton. 1976.

 

Rapoport AM, Sheftell FD. Headache Disorders, A Management Guide For Practitioners, Philadelphia, WB Saunders and Co. 1996; 29.

 

Rayman, RB, Clinical Aviation Medicine, 3rd edition, Castle Connolly Graduate Medical Publishing, LLC, 2000, pp. 65-69.

 

Rizzo M and Tranel D (eds): Head Injury and Post concussive Syndrome. New York, NY, Churchill Livingstone. 1996.

 

 

Updated: 2/23/11