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individual with arterial dissection has no recurrence in one year, risk recurrence thereafter is less than
one per cent per year. Lacunar stroke associated with hypertension-related small blood vessel disease
may allow medical certification after one year, whereas stroke due to atherothrombotic disease with risk
factors might allow medical certification after two years. In some instances, medical certification may
never be appropriate.
Haemorrhagic Stroke
The vast majority of intracerebral, parenchymal haemorrhages occur in hypertensive individuals. Death or
severe disability ordinarily precludes medical certification. Vascular malformations including cavernous
angiomas may also lead to intracerebral bleeding, sometimes with complete recovery. In some instances,
surgical cure is accomplished, allowing medical certification. Though surgical cure of a vascular
malformation might preclude re-bleeding, the risk of residual seizures may still bar certification.
Operational limitations:
Haemorrhagic stroke is disqualifying for all classes of medical certification.
ICAO Preliminary Unedited Version — October 2008 III-10-10
Aeromedical considerations:
Most haemorrhagic strokes occur in individuals with hypertension, and many result in death or severe
disability. There are exceptions in which tissue destruction is minimal and recovery is complete or near
complete. Haemorrhages related to anticoagulants may not result in significant deficit.
If the cause of the haemorrhage can be identified and addressed satisfactorily, medical certification may
be possible once the recurrence risk has been evaluated. The recurrence risk will depend upon the
underlying mechanism. A one to two year observation period is appropriate following haemorrhagic
stroke. A full neurological evaluation indicating satisfactory recovery and freedom from relevant risk
factors may allow medical certification at that time.
Subarachnoid Haemorrhage
Most commonly subarachnoid haemorrhage results from sudden rupture of an intracranial saccular
aneurysm. Aneurysms ordinarily arise from major arteries at the base of the brain (Circle of Willis7) and
are thought to develop from congenital changes in the muscular wall of the artery and degenerative
changes in the internal elastic lamina. Death occurs in 23 per cent, and half of the survivors have
significant disability.
If an individual recovers from aneurismal, subarachnoid haemorrhage and the aneurysm is surgically
isolated from the circulation, medical certification may be considered. Sequelae may include focal
neurological deficit, seizures, and cognitive impairment. Absent these conditions and with a period of
symptom free observation, medical certification may be possible. Surgical cure should be verified by
postoperative angiography.
In some individuals subarachnoid haemorrhage occurs without demonstrable cause. If there is no
recurrence within one year, statistics reveal an acceptably low risk of recurrence thereafter. In another
specific condition, called peri-mesencephalic or pre-pontine subarachnoid haemorrhage, recurrence risk is
low.
Operational implications:
Subarachnoid haemorrhage is disqualifying for all classes of medical certification due to risk of sudden
incapacitation.
Aeromedical considerations:
Successful isolation of the haemorrhagic source from the circulation and freedom from significant deficit
should allow medical certification after one year, during which risk of complications including seizures
declines. Partial obliteration of an aneurysm with residual lumen may present an unacceptable risk. For
subarachnoid haemorrhage of unknown cause, a one year observation period is also warranted. The
presence of a vascular malformation (cavernous angioma, arteriovenous malformation) requires
individual evaluation. Residual malformation, haemosiderin deposition and other factors will affect risk
for recurrent haemorrhage or seizure, and medical certification may not be possible.
7 Circle of Willis: circulus arteriosus cerebri. After Thomas Willis, English anatomist (1621-1675).
ICAO Preliminary Unedited Version — October 2008 III-10-11
TRAUMATIC BRAIN INJURY
Traumatic Brain Injury (TBI) is a major cause of neurological disability in the licence holder population.
Most head injuries, including some with a linear skull fracture, do not involve brain injury. Minimal
criteria for TBI include loss or alteration of consciousness, focal neurological deficit, or cerebral imaging
evidence of injury. Liberal use of modern imaging techniques may indicate parenchymal injury (localized
haemorrhage) in individuals with no clinical signs or symptoms of injury.
The medical assessor becomes involved when the licence holder with TBI has presumably recovered and
　
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本文鏈接地址：Manual of Civil Aviation Medicine 2(29)