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
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
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.
Society of
Fauci AS,
Braunwald E, Isselbacher KJ, Wilson JD, Martin JB, Kasper DL, Hauser SL, Longo
DL, editors.
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.
Matzen R,
Lang R. Clinical Preventive Medicine. Mosby-Year Book, Inc..
AFPAM
48-132: Transient Ischemic Attack, previous edition, USAF School of Aerospace
Medicine,
August 7,
2006