Cryptic asymptomatic parasellar high signal on time-of-flight MR angiography: how to resolve the clinical conundrum.

Abstract

Hyperintense parasellar signal on time-of-flight MR angiography (TOF-MRA) in asymptomatic patients may be due to a variety of nonpathological causes and mimic parasellar high flow signal in pathological arteriovenous shunts at the cavernous sinus (CSAVS). This creates a clinical conundrum between diagnosing an aggressive yet asymptomatic CSAVS subtype against exposing patients without CSAVS to potential complications of an invasive angiographic evaluation. We reviewed common nonpathological causes of hyperintense parasellar signal and contrast their imaging features against those of pathological CSAVS and proposed a systemic approach to resolve such conundrum. The anatomy of the cavernous sinus (CS) and causes of nonpathological parasellar hyperintense TOF-MRA signal are described and explained with case reviews, illustrations, and reference to published literature where appropriate. Imaging features of proven CSAVS are juxtaposed to aid in radiological differentiation. An algorithm is proposed to manage patients with such incidental TOF-MRA findings. The margins, contour, extent, intensity, and stippling appearance aid in evaluation of pathological versus incidental TOF-MRA parasellar signal, and differentiation of CSAVS from nonpathological causes. Pertinent radiological features are summarized in a table. For unresolved cases suspected for CSAVS, further evaluation with dynamic time-resolved contrast-enhanced MRA is proposed and depicted in a decision tree flow chart. Familiarity with the differentiating radiological features and a systematic management workflow could aid in resolving the clinical conundrum of findings of cryptic asymptomatic parasellar TOF-MRA high signal, while facilitating timely detection of the asymptomatic CSAVS.