If complete CNIII involvement with ptosis, mydriasis, and ophtalmoplegia:
Assume a compressive etiology from an intracranial aneurysm (PCOM aneurysm for example)
Proceed to a CTA brain
If complete oculomotor<unk>  palsy without pupil involvement then strongly favor an ischemic process
Consider a CTA brain
Coronal reconstruction on CT will allow visualization of orbits to rule out compressive process
If associated with other neurologic deficits:
CTA brain followed by MRI/MRA brain
Assume a compressive etiology from an intracranial aneurysm (PCOM aneurysm for example)
Proceed to a CTA brain
Consider a CTA brain
Coronal reconstruction on CT will allow visualization of orbits to rule out compressive process
CTA brain followed by MRI/MRA brain
Third nerve palsy
Cataract
Fourth nerve palsy
Lens dislocation
Sixth nerve palsy
Macular disruption
Horner syndrome
Basilar Artery Thrombosis