Computed Tomography Angiography and Computed Tomography Venography
CTA uses a high-speed spiral scanner that provides excellent vessel resolution, with 3-dimensional capability that is complementary to that of MRA. The technique requires use of iodinated contrast dye, employs ionizing radiation, and takes approximately 15 minutes to complete. Sensitivities in the detection of aneurysms wider than 3 mm in diameter or stenosis greater than 70% are approximately 95%. Some medical centers prefer the use of CTA to MRA for the detection of cerebral aneurysms, including those causing an ocular motor cranial nerve (CN) palsy (see Chapter 7, Fig 7-9). New multidetector CTA techniques can accurately detect aneurysms greater than 3–4 mm in diameter in nearly all patients with CN III palsies. CTV is an excellent imaging modality for visualizing the cerebral venous system and is less susceptible to artifacts in comparison to MRV.
Figure 2-13 Venous sinus thrombosis. A, Postcontrast axial CT scan shows a right-sided transverse sinus thrombosis (arrows). B, The magnetic resonance venography scan with contrast shows a complete thrombotic occlusion of the right transverse sinus (arrows).
(Courtesy of Paul H. Phillips, MD.)
Mathew MR, Teasdale E, McFadzean RM. Multidetector computed tomographic angiography in isolated third nerve palsy. Ophthalmology. 2008;115(8):1411–1415.
von Kummer R, Dzialowski I, Gerber J. Therapeutic efficacy of brain imaging in acute ischemic stroke patients. J Neuroradiol. 2015;42(1):47–54.
Excerpted from BCSC 2020-2021 series: Section 5 - Neuro-Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.