Risk of aneurysm based on internal and external dysfunction of the third nerve

Internal and external dysfunction	Risk of aneurysm	Recommendation
Complete internal dysfunction ("pupil blown")
With complete external dysfunction	Highest	MRI/MRA (CTA) catheter angiogram
With incomplete external dysfunction	Highest	MRI/MRA (CTA) catheter angiogram
Without external dysfunction	Minimal	No imaging
Incomplete internal dysfunction ("partial pupil")
With complete external dysfunction	Uncertain, probably low	MRI/MRA (CTA) consider catheter angiogram
With incomplete external dysfunction	Uncertain, minimal	MRI/MRA (CTA) consider catheter angiogram
Without external dysfunction	Minimal	No imaging
No internal dysfunction ("pupil not involved")
With complete external dysfunction	Low if isolated	Observe
With incomplete external dysfunction	Uncertain	MRI/MRA (CTA) consider catheter angiogram

Aneurysm_risk_in_CN3_palsy.htm

MRA: magnetic resonance angiography; MRI: magnetic resonance imaging; CTA: computed tomography angiography.

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