Background: The atlas (C1) vertebra can present with congenital bony bridges, known as ponticuli, which transform the vertebral artery groove into a complete or partial foramen. The most common variant is the ponticulus posticus (arcuate foramen), with the ponticulus lateralis occurring less frequently. The clinical significance of these structures is highly debated, with some evidence suggesting they contribute to vertebrobasilar insufficiency, headaches, and neck pain, while other findings indicate they are benign anatomical variations.

Objectives: This review aims to synthesize the current body of knowledge from key radiographic and anatomical studies to provide a comprehensive overview of the prevalence, morphology, and clinical significance of ponticulus anomalies of the atlas vertebra.

Methods: A structured review of 25 foundational anatomical, radiographic, and clinical studies was conducted. Data regarding the prevalence, morphometry, laterality, and reported clinical correlations of atlas ponticuli were extracted, collated, and synthesized to form a cohesive analysis.

Results: The reported prevalence of ponticulus posticus varies widely in the literature, ranging from approximately 4% to over 30% depending on the population and study methodology. These can be complete or incomplete, and unilateral or bilateral. The ponticulus lateralis is a significantly rarer finding. Morphometric studies have detailed the dimensions of the resulting foramina. Several clinical reports associate these anomalies with symptoms of vertebrobasilar insufficiency, proposing vertebral artery compression as the primary mechanism, though studies comparing symptomatic and asymptomatic cohorts have yielded conflicting results.

Conclusion: Atlas ponticuli are common anatomical variants, not rare pathologies. While their presence may predispose certain individuals to neurovascular symptoms, a definitive causal relationship remains unsubstantiated across the general population. Awareness of these variations is critical for clinicians, particularly surgeons and manual therapists, to prevent iatrogenic injury and to consider in the differential diagnosis of craniofacial pain and vertigo syndromes.

Atlas, C1 Vertebra, Ponticulus Posticus

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