Table 1:

Mimics of near-occlusion on conventional angiography and CTA

Cause	Mimic	Way to Separate/Reason for Mimic
Similar appearance, but not atherosclerosis	Dissection	Cervical ICA lesion without severe bulb stenosis, possibly patient history
	High ICP	Patient history, likely no focal stenosis
	Postradiation disease	Patient history, possibly no focal stenosis
	Hypoplasia	No prominent bulb stenosis, narrow bony canal
Imaging protocol	NrOc mistaken for occlusion	Delayed images reveal patent lumen
Interpretation	Occlusion mistaken for NrOc	Ascending pharyngeal artery mistaken for ICA
	Stenosis mistaken for NrOc	Larger opposite ICA from anatomic variations: opposite ICA supplies fetal PCA and/or both ACAs
	NrOc mistaken for stenosis	Partially collapsed NrOc overlooked as a normal lumen when it is not threadlike
	Intracranial disease mistaken for NrOc	Exclude distal disease as cause for the collapse

Note:—PCA indicates posterior cerebral artery; ICP, intracranial pressure; NrOc, near-occlusion; ACA, anterior cerebral artery.