Distinctive patterns on CT angiography characterize acute internal carotid artery occlusion subtypes

Abstract

Noninvasive computed tomography angiography (CTA) is widely used in acute ischemic stroke, even for diagnosing various internal carotid artery (ICA) occlusion sites, which often need cerebral digital subtraction angiography (DSA) confirmation. We evaluated whether clinical outcomes vary depending on the DSA-based occlusion sites and explored correlating features on baseline CTA that predict DSA-based occlusion site.We analyzed consecutive patients with acute ICA occlusion who underwent DSA and CTA. Occlusion site was classified into cervical, cavernous, petrous, and carotid terminus segments by DSA confirmation. Clinical and radiological features associated with poor outcome at 3 months (3-6 of modified Rankin scale) were analyzed. Baseline CTA findings were categorized according to carotid occlusive shape (stump, spearhead, and streak), presence of cervical calcification, Willisian occlusive patterns (T-type, L-type, and I-type), and status of leptomeningeal collaterals (LMC).We identified 49 patients with occlusions in the cervical (n = 17), cavernous (n = 22), and carotid terminus (n = 10) portions: initial NIH Stroke Scale (11.4 ± 4.2 vs 16.1 ± 3.7 vs 18.2 ± 5.1; P < 0.001), stroke volume (27.9 ± 29.6 vs 127.4 ± 112.6 vs 260.3 ± 151.8 mL; P < 0.001), and poor outcome (23.5 vs 77.3 vs 90.0%; P < 0.001). Cervical portion occlusion was characterized as rounded stump (82.4%) with calcification (52.9%) and fair LMC (94.1%); cavernous as spearhead occlusion (68.2%) with fair LMC (86.3%) and no calcification (95.5%); and terminus as streak-like occlusive pattern (60.0%) with poor LMC (60.0%), and no calcification (100%) on CTA.Our study indicates that acute ICA occlusion can be subtyped into cervical, cavernous, and terminus. Distinctive findings on initial CTA can help differentiate ICA-occlusion subtypes with specific characteristics.

Figure 1

A flow diagram of the enrolled patients. A total of 191 consecutive patients with acute ischemic stroke from a prospective digitalized thrombolysis database over 3 years. ACA = anterior cerebral artery, CTA = computed tomography angiography, DSA = digital subtraction angiography, MCA = middle cerebral artery.

Figure 2

Dotted circles and squares indicate 4 characteristic findings on initial computed tomography angiography: carotid occlusive patterns (stump, spearhead, and streak), presence of cervical calcification, occlusive patterns of the Willisian circle (T-type, L-type, and I-type), and status of leptomeningeal collaterals (poor and fair or good).

Figure 3

(A) The frequency of characteristic patterns (carotid occlusive patterns, presence of carotid calcification, occlusive patterns of the Willisian circle, and status of leptomeningeal collaterals) on initial CTA according to the DSA-confirmed ICA occlusion site. CTA shows distinctive characteristics according to the DSA-confirmed ICA occlusion sites. (B) ROC curves using the characteristic patterns on initial CTA to differentiate the actual DSA occlusion sites. Composite scores of 4 characteristic patterns show the highest areas in the ROC curves for pinpointing the ICA occlusion site: (a) cervical portion, (b) cavernous portion, and (c) terminus portion. CTA = computed tomography angiography, DSA = digital subtraction angiography, ICA = internal carotid artery, ROC = receiver operating characteristic.

Figure 4

“Spearhead” formation (A) and “absent or stump” formation (B) in patients with ICA occlusion. “Spearhead” is shown in 3D-reconstruction (a) and MIP (b) images on initial CTA. Its trajectory on DSA is observed approximately 30% longer in the same patient during handed injection with iodine contrast at the level of the common carotid artery than the trajectory on CTA (c). The cavernous portion on DSA is the actual occlusion site in this patient (d), although initial CTA occlusion indicates the cervical portion. (B) Three-dimensional reconstruction CTA shows absence (e) and rounded stump (f) of the occluded ICA with calcification (dotted circle). 3D = 3-dimensional, CTA = computed tomography angiography, DSA = digital subtraction angiography, ICA = internal carotid artery, MIP = maximum intensity projection.