Craniovertebral Junction Anomaly with Atlas Assimilation and Reducible Atlantoaxial Dislocation: A Rare Constellation of Bony Abnormalities

Abstract

A rare case of craniovertebral junction anomaly with associated reducible C₁-C₂ dislocation and assimilation of the atlas is reported. The patient presented with neck pain with spastic quadriparesis. A posterior stabilization utilizing a contour rod, sublaminar wire fixation and onlay bone grafts between the occiput, and C₃ and C₄ vertebrae was performed followed by symptomatic improvement.

Congenital absence of the posterior arch of the atlas associated with a fracture of the anterior arch

“…15 These clinical deficits, have been attributed to anomalies in the cartilaginous development of the posterior arch rather than to disturbances of ossification. 16 Total or partial aplasia of the posterior atlas arch is rare. Although generally asymptomatic, it may cause neck pain and there is a very rare subset of young patients who develop chronic neurological deficits and atlantoaxial instability.…”

The Incidence and Clinical Implications of Congenital Defects of Atlantal Arch

“…This is supported by findings at autopsy or intra-operatively that connective tissue bridges the bony defect 26) . Congenital anomalies of the atlantal arch frequently occur with various combinations of neural abnormalities, suggesting an interrelationship exists 21) . Common associations include gonadal dysgenesis, Klippel-Feil syndrome, Arnold-Chiari malformations, and Turner and Down syndrome 28) .…”

Bipartite Atlas –A Rare Entity, a Study of Its Incidence in North Indians

“…Congenital anomalies of the atlantal arch frequently occur with various combinations of bone and spinal cord abnormalities, suggesting an interrelationship exists. [19] In our study [ Table 2] shows the associated anomalies One patient (patient 1) had associated cleft palate, patient 2 also had absent seventh cervical spine pedical, while 3rd pt showed partial posterior posticulus None of the reviewed patients of bipartite atlas had neurological deficits because of atlantal arch anomalies but off and on cervical neck pain with radiation in arm, relieved by analgesics was common. The CT scans of the patients show midline clefts of the anterior and the posterior arches of C1 with similar imaging features: smooth margins lined by Section: Anatomy cortical bone and no lateral offset.…”