Complete bilateral arcuate foramina and atlantoaxial subluxation

Abstract

Letter to the Editor A cadaveric specimen undergoing a posterior cervical dissection was noted to have complete bilateral ossification of the posterior atlanto-occipital membrane over the vertebral artery groove and a type-1 atlantoaxial subluxation—atlas rotation on the odontoid process with no anterior displacement (Fig. 1). This ossification anomaly, known as Kimmerle’s variant, ponticulus posticus, arcuale foramen, and/or arcuate foramen, is found with partial and complete ossification in 6– 18 % and 4–8 % (3.3–6.7 % unilateral, 0.7–1.3 % bilateral) of the population, respectively, with a debated higher reported prevalence in females [2, 4, 7, 9]. This anomaly often remains asymptomatic; however, compression of the neurovascular structureswithintheforaminacaninducepressurephenomena of the periarterial sympathetic plexus, especially when rotating the head, and induce vertebro-basilar insufficiency and/or clinical symptoms resembling Barre–Lieou syndrome, presenting with shoulder-arm and neck pain, cervical migraine, hearing loss, vertigo, and/or loss of consciousness [2, 5, 7]. Theaverageageatclinicalpresentationhasbeendebatedin the literature, and has been reported to be greatest between 11 and 20 years and 21–30 years, while another study indicated that presentation is most common during the third and fourth decades of life [5, 8]. Though it is possible that ossification progresses over time, arcuate foramina have been reported in children as young as 2 years of age with one study reporting four cases of partial and three cases of complete arcuate foramina in children younger than 10 years of age [1, 6]. Awarenessofthisdysmorphicfeatureisbothmedicallyand surgically relevant, as intraoperative injury to the vertebral artery can result in disastrous neurological complications and deficits. Knowledge of any variations in the course of the vertebral artery or in the morphology of the posterior vertebral arch is of critical importance when performing instrumentation involving C1 or surgery of craniocervical junction [7]. Preoperative CTangiography has been recommended in order to preclude to the possibility of misidentifying an arcuate foramen as a broad lamina or widened posterior arch, and risking injury to the vertebral artery [3, 12]. Several studies, with positive findings, have examined surgical excision of the arcuateforamenwithdecompressionofthevertebralarteryfor