Clinical Practice Guideline

for

CEREBROVASCULAR DISEASE

Developed for the

Aerospace Medical Association

by their constituent organization

American Society of Aerospace Medicine Specialists

 

Overview:  Symptomatic cerebrovascular disease is considered disqualifying for all flying duty classes in both the military and civilian flying populations.  Cerebrovascular disease (CVD) for purposes of this practice guideline includes conditions such as transient ischemic attacks (TIA) including amaurosis fugax , stroke, subarachnoid hemorrhage (SAH), and similar conditions or their sequelae.  The policy statement must generalize recommendations given the wide diversity of conditions.

 

Pathogenesis for CVD is varied.  Possible conditions include: (1) processes intrinsic to the blood vessels, such as atherosclerosis, vasculitis, aneurysms, and arterial dissection; (2) from a remote source, e.g., embolus from a heart anomaly; (3) decreased arterial perfusion; (4) increased blood viscosity as can be seen with some anemias, malignancies, blood dyscrasias, severe dehydration; and (5) rupture of an intracranial blood vessel.

 

The differential diagnosis may include seizures and post-ictal phenomena, migrainous phenomena, generalized or global ischemia as in syncope, and a labyrinthine source of vertigo.  Intracranial tumors, vascular malformations, and intracranial hemorrhage could also mimic a TIA.

 

CVD is the third leading cause of death in the United States and accounting for some 140,000 deaths annually.  The risk factors for CVD include hypertension (most important), coronary artery disease, smoking, obesity, increasing age, hyperlipidemias, arrhythmias, coagulopathies or other hematologic conditions, and diabetes.

 

Individuals with carotid artery stenosis are at a higher risk for stroke, heart attacks, and death.  The risk increases even if these individuals are asymptomatic; however, those with symptoms, such as TIA or amaurosis fugax, are at considerably higher risk for sudden incapacitation.  Given the broad range of possible conditions classified under CVD it would be impossible to give an overall assessment of risk for incapacitation.  Nevertheless, specific comments can be made with respect to the most common conditions.

 

Stroke is the generic term that accounts for cerebrovascular conditions of hemorrhagic or ischemic nature.  In one population-based study, cerebral infarction accounted for approximately 85% of all strokes.  Of these, 60% were due to emboli from the cervico-cephalic circulation and 40% were due to cardiac emboli.

 

Five percent of the population 65 and older may be impacted by strokes; some 400,000 hospital discharges of stroke survivors occur annually.  Approximately 0.5% of people over age 50 and 10% of those over age 80 have carotid artery stenosis greater than 50%.  However, in a study of stroke victims over age 60, only 13% were noted to have significant, i.e., greater than 70% occlusion, carotid artery stenosis.  Carotid bruits were a fair indicator of vascular disease, but a poor predictor of future ischemic strokes.  Overall, persons with carotid artery disease were more likely to die from coronary artery disease than from a stroke.

 

Annual incidence of stroke on the ipsilateral side of a bruit without previous TIA has been estimated at approximately 1-3%.  The risk for stroke in an individual with TIAs has been estimated to be 4-12% annually, and the risk for death is 10-17% per year.  Individuals with the sole presenting complaint of amaurosis fugax have a risk for cerebral infarction of about 2% per year, with a 7-8% possibility of having a recurrent retinal TIA during the same time period. 

 

The most frequent identifiable causes of SAH are a ruptured berry aneurysm or bleeding from an arteriovenous malformation; however, up to 15% may have no identifiable cause and are believed to be venous in origin (referred to as perimesencephalic).  Almost a quarter of these individuals die within 24 hours of the event; of the survivors, another 25% may die within 6 months from sequelae of the condition. 

Aeromedical Concerns: Symptoms of CVD generally are abrupt, typically unrelated to any particular physical activity, and depend on the underlying condition and the neurological distribution of the blood vessel concerned.  Symptoms may include weakness, paresthesias, speech disturbance, visual deficit, vertigo, ataxia, loss of consciousness, permanent neurologic and cognitive impairment and sudden death.  Because of the high risk for recurrence, subsequent stroke or myocardial infarction, and the usually sudden and often incapacitating nature of symptoms and signs, CVD present a very significant concern in the aerospace environment.

 

All three military services preclude their pilots from flying after they have had any type of CVD.  In certain circumstances when a specific cause has been identified and corrected, e.g., arterial dissection and suspected paradoxical embolism from PFO, and no sequelae remain; select pilots may be considered for waivers under very special circumstances.

 

In the civilian aviation community a cerebrovascular event or therapeutic procedure, while initially disqualifying, does not automatically preclude an airman from eventually gaining a medical certificate for any class.  Since the civil aviation medicine folks will consider such cases for medical certification they are interested in also determining whether there is associated cardiovascular disease.  Thus, they require a complete cardiovascular work up. This should include a consultation from their treating physician, 2 D echocardiogram and maximal stress testing.  They also would like bilateral carotid Doppler screening performed.

 

The predominant aeromedical concern is CVD presenting as sudden catastrophic event with complete incapacitation of a pilot.  Additionally, subtle incapacitation that affects cognitive ability and memory, while not as dramatic, nevertheless can have significant impact on aviation safety.  As with coronary artery disease, sudden death may be the initial manifestation of CVD in some individuals.  Also, of particular concern are the short-lived, repeated TIAs with minimal symptoms that go unreported to healthcare practitioners and may end in sudden death or a disabling stroke.  Detecting the asymptomatic progression of CVD reliably without frequent monitoring and expensive testing, invasive or otherwise, is another aeromedical concern.

 

Treatment and Aeromedical Disposition: Medical treatment primarily consists of antiplatelet or anticoagulation therapy, or control of cardiac arrhythmias.  When surgical treatment is applicable,   carotid endarterectomy, correction of vascular cerebral anomalies, or correction of cardiac defects are the typical procedures encountered.  Screening and diagnostic test utilized range from simple carotid auscultation to magnetic resonance imaging, ultrasonography and angiography.

 

Military pilots with documented CVD are rarely, if ever, granted waivers in any U.S. military service.

 

Civilian airmen who wish to be granted medical certification after the diagnosis of CVD or after a specific event, such as a TIA or stroke, must wait for 24 months prior to any attempt at gaining Federal Aviation Administration (FAA) certification.  If after that time frame they have remained asymptomatic and no significant sequelae exist they may request consideration for certification under the Authorization for Special Issuance (i.e., waiver) process.  If during the work up there is discovered a definitive etiology for the event and it is adequately treated, then it possible to gain medical certification after one year of observation.  The best example would be in the case of carotid artery disease and carotid endarterectomy.  Recently, they have begun to grant medical certification to airmen with proven lacunar infarction, providing the airman has adequately demonstrated adequate treatment. 

 

All civilians with suspected or confirmed CVD must be thoroughly evaluated by one or more specialists.  As minimum complete cardiovascular and neurologic evaluations with documentation of past medical and family history, risk factor assessment, and physical examinations will be required.  Laboratory studies should include blood chemistries, coagulation studies, lipid profiles, complete blood counts, urinalysis, and any other studies deemed necessary.  Imaging studies may include MRI or MRA scans of the head, with or without contrast, carotid ultrasounds, carotid angiograms, echocardiography, electrocardiograms, and Holter studies (if necessary).  All associated films and tracings must be provided for review by the aeromedical consultants.  In select cases additional cardiac workups such as a stress test or cardiac radionuclide studies may be requested.

 

Experience:  Review of data from the computer system at the FAA revealed that in August 2006, the Aerospace Medical Certification Division had 342 first-, 339 second- and 1,064 third-class airmen currently issued medical certificates to individuals previously diagnosed with CVD, that had been treated and were considered in remission.

 

A search of the USAF ACS database for those pilots with at least one reference diagnosis of TIA revealed that 51 aviators have been evaluated.  While 11 (22%) of these were granted waivers, a more careful record review revealed that only four (8% of total) had true transient ischemic events; the others were due to migraine, presyncope, vasovagal response, transient ischemia during cardiac catheterization, or +Gz-induced loss of consciousness (G-LOC). In all four cases, the events were solitary and brief, with no recurrence and in no case was there a confirmed cause due to vascular thrombosis or embolism.  No other CVD condition was waivered.

 

References:

 

U. S. Preventive Services Task Force.  Guide to Clinical Preventive Medicine Services, 2nd edition.  U.S. Department of Health and Human Services.  Washington, DC. 1990.

 

Society of U.S. Naval Flight Surgeons.  Aeromedical Reference and Waiver Guide.  Naval Operational Medicine Institute. Pensacola, Florida. 1999.

 

Fauci AS, Braunwald E, Isselbacher KJ, Wilson JD, Martin JB, Kasper DL, Hauser SL, Longo DL, editors.  Harrison’s: Principles of Internal Medicine. Fourteenth Edition.  McGraw Hill, Inc.  New York. 1998.

 

Braunwald E, Fauci AS, Isselbacher KJ, Kasper DL, Hauser SL, Longo DL, Jameson JL, editors.  Harrison’s: On-Line; Part 14, Section 2, Chapter 366 - Cerebrovascular Diseases. McGraw Hill, Inc.  New York. 2000.  www.harrisonsonline.com

 

Matzen R, Lang R.  Clinical Preventive Medicine.  Mosby-Year Book, Inc..  St. Louis, Missouri.  1993.  Pages 857-867.

 

AFPAM 48-132: Transient Ischemic Attack, previous edition, USAF School of Aerospace Medicine, Brooks AFB, TX, 1995.

 

 

 

August 7, 2006