title: Imaging of intracranial aneurysms causing isolated third cranial nerve palsy.
abstract: Isolated third cranial nerve palsies may be caused by compressive intracranial aneurysms located at the junction of the internal carotid and posterior communicating arteries or, less commonly, at the apex of the basilar artery or its junction with the superior cerebellar or posterior cerebral arteries. Such aneurysms typically measure at least 4 mm in diameter. Technical improvements in noninvasive techniques, including CT and MRA, have yielded a detection rate of such aneurysms that approaches that of catheter cerebral angiography (CCA), which itself carries a small but serious risk. Multidetector technology, which allows a rapid scan time, has promoted CT to the first choice for investigating aneurysms in this setting except when dye or radiation exposure is unacceptable, as with pregnant women, children, and those with renal or severe cardiac disease. Major impediments to accurate detection are a lack of availability of trained technicians, who must perform manipulation of the raw imaging data ("post-processing"), and a paucity of certified neuroradiologists with the time, skill, and experience to devote to interpreting difficult cases. To avoid diagnostic mishaps, noninvasive studies should be reviewed by at least one neuroradiologist before aneurysm is rejected as the cause or before the patient undergoes CCA.
authors.affiliation: Department of Radiology, Division of Interventional Neuroradiology, University of Michigan Health System, 1500 East Medical Center Drive, Ann Arbor, MI 48109, USA. neerajc@med.umich.edu
authors.forename: Neeraj
authors.initials: N
authors.lastname: Chaudhary
authors.forename: Indran
authors.initials: I
authors.lastname: Davagnanam
authors.forename: Sameer A
authors.initials: SA
authors.lastname: Ansari
authors.forename: Aditya
authors.initials: A
authors.lastname: Pandey
authors.forename: Byron G
authors.initials: BG
authors.lastname: Thompson
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Gemmete
mesh_terms: D002533:Cerebral Angiography / Q000009:adverse effects / Q000379:methods / Q000592:standards; D002536:Cerebral Arteries / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D003952:Diagnostic Imaging / Q000379:methods* / Q000592:standards; D006801:Humans; D007091:Image Processing, Computer-Assisted; D002532:Intracranial Aneurysm / Q000150:complications* / Q000000981:diagnostic imaging* / Q000473:pathology; D018810:Magnetic Resonance Angiography / Q000379:methods / Q000592:standards; D008507:Medically Underserved Area; D015840:Oculomotor Nerve Diseases / Q000209:etiology*; D011871:Radiology; D000078329:Workforce