A Clinical Classification System for Aberrant Internal Carotid Arteries

Objectives/Hypothesis: Pronounced anatomic variations of the extracranial internal carotid artery (ICA) can be found in 5% to 6% of the general population. An aberrant ICA is at risk of injury during routine pharyngeal procedures if the vessel is placed into close relationship with the pharyngeal wall. The objective was to highlight the impact of parapharyngeal ICA aberrations and to analyze the clinical usefulness of the current anatomic classification system of these anomalies. Study Design: Prospective quality assessment study in an academic tertiary care medical center. Methods: A systematic clinicoradiological follow-up study was performed over a period of 18 months. The ICA's course was classified according to Weibel and Fields in 21 consecutive patients with 35 pronounced parapharyngeal ICA aberrations. The vessels' minimum distance to the pharyngeal wall and the corresponding pharyngeal level was analyzed. Results: Tortuosity was found in 13, kinking in 18, and coiling in 4 aberrant ICAs. The vessel's minimum distance to the pharyngeal wall ranged from 0.8 to 17.9 mm (mean, 7.0 mm), but the currently used anatomic classification was inadequate to determine the risk potential for ICA injury in the given cases. We propose a clinicoradiological classification system, which considers the vessel's relation to the pharyngeal wall. Conclusions: Parapharyngeal ICA aberrations are common and probably under-appreciated anatomic variations: The awareness of these anomalies is essential for clinicians. Since the current anatomic classification is insufficient to outline patients with an increased risk of ICA injury, a clinicoradiological graduation of cervical ICA aberrations may be of practical benefit.