Congenital malformed posterior arch of atlas with fusion defect: a case of developmental canal stenosis causing cervical myelopathy

Abstract

Congenital anomalies of the posterior arch of the atlas (PAA) are usually asymptomatic and diagnosed incidentally. Very rarely, they present with cervical myelopathy, usually being associated with partial aplasia or agenesis of PAA. We describe a 44-year-old lady with cervical myelopathy secondary to a malformed PAA with developmental atlas-level spinal stenosis and a congenital posterior fusion defect with persistent midline cleft showing significant non-osseous fibro-cartilaginous hypertrophy, causing critical cord compression. Spinal decompression by en-bloc wide excision of anomalous arch with occipito-cervical fusion was performed. Post-operatively, the patient's neurology improved gradually over 12 months, with radicular symptoms being the earliest and gait disturbance being the last symptom to resolve. At 24 months, she was asymptomatic with imaging showing good spinal cord decompression at the level of atlas. Developmental atlas stenosis with hypertrophic posterior arch fusion defect is an unusual cause of cervical myelopathy, which can be effectively treated with decompression with/without stabilization. Being aware of such an entity can avoid diagnostic dilemma and facilitate prognostication of outcomes, accurate surgical planning in the stenotic segment thereby ensuring effective management of these patients.

Percutaneous full endoscopic C1 laminectomy for developmental atlantal stenosis with myelopathy: a case report of three cases and review of the literature

“…However, in adults, the main deformities are usually an asymmetric structure, abnormal bone hyperplasia, and inborn spinal canal stenosis with complete PAA (30,31). On rare occasions, it can also show dysmorphic features with failure of fusion of the two hemi-arches with a midline cleft as reported by Shah et al (5) in a 44-year-old female. We speculate DASM may be related to genes and age, and the deformity develops incrementally with age.…”

“…Subsequently, in 1994, seven cases of cervical myelopathy caused by aplasia of the posterior arch of the atlas (PAA) were reported by Currarino (4). Shah et al (5) and Bhattacharjee et al (6) also described similar cases of abnormal development of the C1 posterior arch which led to stenosis of the spinal canal. However, almost all of the relevant articles were case reports.…”

“…The development of atlantal stenosis involves several factors, among which a genetic cause is one of the most important (16). The occurrence of atlas developmental malformation is more common in patients with Chiari malformation, Down syndrome, Klippel-Feil syndrome, Noonan syndrome, Williams syndrome, diffuse idiopathic skeletal hyperostosis (DISH), atlanto-axial instability, and atlantoaxial subluxation with or without os odontoideum (4,5,(17)(18)(19)(20)(21)(22)(23)(24). Stenosis secondary of C1 without trauma and atlantoaxial instability is a possible pathophysiologic factor, which may be secondary to atlas hypoplasia, ossification of the posterior atlantoaxial membrane (PAAM) (20), or ossification of the transverse atlantal ligament (OTAL) (25) that lead to consistent space reduction of the spinal cord.…”

“…While anomaly of the PAA is an easily overlooked cause of symptomatic cervical myelopathy, its clinical symptoms can be very severe. The symptoms of DASM are complex and diverse, including occipital neuralgia, occipitocervical pain, paresthesia and weakness of limbs, gait disturbance, poor fine motor skills and difficulties in holding or grasping, urinary incontinence, ataxia, and apnea (5)(6)(7)(8)10,21,31,33,37). Certain cervical positions can induce or exacerbate these symptoms, and movement restrictions in the upper cervical spine can be observed in some patients.…”

Classification and Surgical Treatment of Developmental Spinal Canal Stenosis at Atlas Level

“…The atlas was located at the junction of the cranial and cervical regions. Developmental spinal canal stenosis is relatively rare at the upper cervical level than at lower cervical level 10 . Diagnosis of DSSA is mainly based on cervical CT and MRI results, and clinical symptoms 8,9,11,12 .…”