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A retropharyngeal internal carotid artery (RP-ICA) is a cervical ICA variant that courses adjacent to or abuts the pharyngeal wall, reducing the safety margin during procedures such as nasotracheal intubation and transoral surgery. Although described for over a century, relatively few cohort studies have investigated its prevalence, and no pooled estimate has been established. Following PRISMA guidelines, we systematically searched PubMed, Embase, Scopus, Web of Science, and Google Scholar (as of August 2025) for adult imaging cohorts that reported both the numerator (RP-ICA cases) and the denominator. Two reviewers independently performed study screening and data extraction. Exclusion criteria included non-ICA vascular variants, studies of low quality, those written in languages other than English, and those with unavailable full text. The risk of bias was assessed using a modified Newcastle-Ottawa Scale. Study-specific proportions were logit-transformed and pooled using a DerSimonian-Laird random-effects model with 95% confidence intervals (CI). Of 743 records identified, 595 titles/abstracts were screened and 89 full texts assessed; 47 studies were included qualitatively, and five imaging cohorts were meta-analyzed. Across these cohorts, 150 RP-ICA cases were identified among 10,066 adults. Prevalence in individual studies ranged from 0.07% to 7.97%. The pooled prevalence was 1.51% (95% CI, 0.53%-4.21%), with substantial heterogeneity. The oropharynx was the most frequent site of RP-ICA. Several reports described carotid arteries within a few millimeters of the pharyngeal mucosa or in direct contact, and positional changes were observed on serial imaging. The qualitative synthesis detailed pharyngeal level, laterality, and carotid-pharyngeal distances. Original imaging evidence of cases involving multiple RP-ICAs and additional carotid segments was further reported. RP-ICA is an uncommon but clinically significant vascular variant. Standardized reporting of minimum carotid-pharyngeal distance, pharyngeal level, laterality, and core imaging parameters would enhance comparability across studies and facilitate risk communication in otolaryngology, anesthesia, dentistry, vascular surgery, and spine surgery.
Tudose et al. (Sat,) studied this question.