Atlantoaxial Subluxation due to an Os Odontoideum in an Achondroplastic Adult: Report of a Case and Review of the Literature

Abstract

The authors report the first example of an adult achondroplastic dwarf with progressive quadriparesis secondary to atlantoaxial subluxation as a consequence of an os odontoideum. Actually, craniocervical region is a frequent site of compression and myelopathy in achondroplasia particularly in children as a result of small foramen magnum and hypertrophied opisthion. Moreover, very rarely in achondroplastic patients, coexistence of atlantoaxial instability as the sequel of os odontoideum can result in further compression of the already compromised cervicomedullary neural tissues, the scenario that has been reported only in five achondroplastic children. Herein, a 39-year-old achondroplastic male suffering such an extremely rare combination is presented. With C1-C2 screw rod instrumentation, atlas arch laminectomy, limited suboccipital craniectomy, and release of dural fibrous bands, reduction, decompression, and stabilization could be achieved properly resulting in steady but progressive recovery.

Os Odontoideum: Review Article

“…5,10 The implication of OO in individuals suffering from Down syndrome and skeletal dysplasia, such as Morquio disease, multiple epiphyseal dysplasia, achondroplasia, pseudoachondroplasia, Larsen syndrome, and chondrodystrophia calcificans congenital are in favour of its congenital etiology. 9,72,78,79 The association between OO and achondroplasia was first reported by Gulati and Rout in 1974, and since then, 5 more children with related symptoms have been reported. 9 However, this coexistence in achondroplastic adults is an extremely rare occurrence and has been reported in the intensive research undertaken by Rahimizadeh et al in 2015.…”

“…9,72,78,79 The association between OO and achondroplasia was first reported by Gulati and Rout in 1974, and since then, 5 more children with related symptoms have been reported. 9 However, this coexistence in achondroplastic adults is an extremely rare occurrence and has been reported in the intensive research undertaken by Rahimizadeh et al in 2015. 9 In 1999, Taggard et al reported the study of 33 patients with Down syndrome who had craniocervical instability.…”

“…8 The ability to manage the possible cases of OO is determined by the stability of atlantoaxial joint. 8,9 While OO under stable conditions might be considered for close observation and periodic radiological assessment, prophylactic stabilization might be considered for examining asymptomatic conditions with implied instability. 5,9 Thus, instability, which characterizes the asymptomatic condition of OO, may put the patient at a risk of developing significant spinal cord injury even when subjected to minor trauma.…”

“…8,9 While OO under stable conditions might be considered for close observation and periodic radiological assessment, prophylactic stabilization might be considered for examining asymptomatic conditions with implied instability. 5,9 Thus, instability, which characterizes the asymptomatic condition of OO, may put the patient at a risk of developing significant spinal cord injury even when subjected to minor trauma. 1,2,[4][5][6][7]10 However, the cardinal cause underlying the signs and symptoms of a patient with neurological deficits is attributed to atlantoaxial instability, which demands surgical intervention.…”

“…These studies indicated that following the first instance of OO with myelopathy reported by Wollin in 1963, 9 more cases have been published. 9,40,84 Clinical picture: Although OO has a clear definition, its clinical manifestations are variable among patients defined by the spectrum of severity of symptoms ranging across the categories of being completely asymptomatic or with neck pain to severe cervicomedullary myelopathy. In fact, patients with OO might remain asymptomatic throughout their life or become symptomatic as early as in childhood.…”