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AEROMEDICAL DECISION MAKING IN CEREBRAL ANEURYSMS
Pooshan Navāthé Michael Drane Peter Clem David Fitzgerald
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Disclaimer I receive a salary from the Commonwealth of Australia.
I have no financial relationships to disclose.
I will not be discussing drugs and off label use.
I will try to fairly represent the Policy and Practice of the Civil Aviation Safety Authority (Australia), and to clearly indicate where I am straying into personal/professional opinion for which I, and I alone, am responsible
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“Aneurysm is an abnormal local dilatation in the wall of a blood vessel…”
Most subarachnoid haemorrhages are caused by ruptured saccular aneurysms.
Important because of acute onset and incapacitation
Only about one-third have a “good outcome”
Aeromedical Significance
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Yellow Flag
Likelihood of clinical event
Likelihood of Aviation event
Risk acceptable?
Incidence & Prevalence
data Characteristics
, Aeromedical factors
FLY
Not FLY
Manage Likelihood
Manage Consequence
Reassess - Risk acceptable?
Yes
No
No
Rx, Maintenance, Surveillance,
Time
Limit privileges
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Incidental finding • 3.2% population, (Vernooij 2007,
Vlak 2011) 20-30% multiple (Stehbens 1963)
• Mean age 50 • Gender M=F, but F>M over 50yrs • 85% anterior circulation, mainly
Circle of Willis at arterial junctions Post-rupture
Likelihood of clinical event
Presentation
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Associated hereditary conditions • Polycystic kidney (6.9X risk) • Connective tissue disorder
• Ehlers-Danlos • Pseudoxanthoma elasticum
• Familial aldosteronism Tp 1 • Alpha1 antitrypsin deficiency
Likelihood of clinical event
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• Aneurysmal subarachnoid haemorrhage 6 – 16/100,000 [Sarti C 1991]
Risk of rupture • Size • Rate of enlargement • Location & initial size • Hypertension / Cigarette smoking
/Œstrogen deficiency Post-treatment complications
Likelihood of clinical event
Incidence / prevalence data
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In aneurysms as in fishing
Likelihood of clinical event
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Size of Aneurysm
International Study of Unruptured Intracranial Aneurysms [ISUIA 2003] • 6544 pt –years, • mean 4.1 yrs
follow-up
Size Rupture Risk p.a.
<7mm 0.1% 7 – 12mm 0.5% 13 – 24mm
3%
>25mm 8%
Likelihood of clinical event
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Size of Aneurysm
Aneurysm Verification Study [Sonobe 2010] • 1306.5 pt-years, • mean 3.4yrs
follow-up
Size Rupture Risk p.a.
<5mm 0.54% Single 0.34% Multiple 0.95%
Likelihood of clinical event
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Likelihood of clinical event
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Location Percent of Aneurysms Enlarging (Mean 17.7 months)
Middle Cerebral A 0%
Internal Carotid A 8.8%
Basilar A bifurcation 40%
Initial Size 2 - 4mm 2.4%
5 – 9mm 9.1%
10 – 20mm 50% [Matsubara S 2004]
Circle of Willis
Likelihood of clinical event
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Treatment • Monitor
• Annual CTA or MRA to demonstrate stability, then @2-3 years
• Surgical clipping • Hospital mortality 1.6%1
• Morbidity & mortality at 1 year: 30.9% • Endovascular repair (2D and 3D coils)
• Hospital mortality 0.6%1, • Recurrence 5 – 15% in 1st 6months • Morbidity & mortality at 1 year: 23.5%
Alshekhlee 2010 - Stroke. 2010; 41: 1471-1476
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Complications: Post-operative Seizures
[Hart 2011]
Predictors of risk for a seizure
Hazard ratios
Neurosurgery 1.64 Younger age 1.54 Neurological deficit 2.1 Thromboembolic complications
5.1
Neurosurgical group had increased seizure risk up to 14 years after clipping, compared with the endovascular group.
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Non-MCA Treatment
After 1 Year After 2 Years
Surgical Clipping 1.5% 0.4%
Endovascular 1.8% 0.8%
Post-operative seizures in patients with good recovery at 2 months
MCA Treatment After 1 Year After 2 Years Surgical Clipping 10.5% 3.5%
Endovascular 3.4% 2.6% [Hart 2011]
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Aviation environment • Hypoxia & fatigue – increase
seizure risk • ?”Stress”
Human performance • Acute onset total incapacitation • Cognitive and executive
impairment
Likelihood of Aviation event
Talking aeroplane
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Low Risk - 5mm or less diameter High risk Larger than 5mm Enlarging Multiple aneurysms with > or = 4 mm Previous subarachnoid haemorrhage <50 years old, hypertensive or family
history
CASA Paradigm: Incidental finding
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CASA Paradigm: Incidental finding Risk Class Certification Surveillance
Low Risk
1, 3 Multi-crew 1Y Annual neurosx RV
2 Unrestricted 1Y
Annual neurosx RV
High Risk
Case - by - case
Initial certification requires demonstration of stability eg Rpt CTA/MRA at 6 – 12 months
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Low risk = <2% seizure risk at one year: Non Middle Cerebral A aneurysm Either clipping OR endovascular coiling No complications at 2 months post-op.
High risk include: Middle cerebral artery aneurysms Op complications / thromboembolism /
ischaemic damage Larger subarachnoid haemorrhages (Fisher
Grade >1)
CASA Paradigm: Post-treatment
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CASA Paradigm: Post-treatment
Risk Class Stand-down
Certification Surveillance
Low Risk
1, 3 2Y 1Y Multi-crew
Annual RV
2 1Y 1Y With safety pilot
Annual RV
High Risk
Case - by - case
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Cerebral aneurysms common - not all bleed Bleeding aneurysms - high mortality and morbidity High risk features (history) Familial conditions Past history of SAH Multiple
ID low risk group (incidental, location, post Rx) permits medical certification.
High risk group (MCA or Rx with complications) carries significant risk of seizure which may persist for at least 14 years.
Summary
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