Abstract

Study design: Follow-up following conservative treatment for isolated laminar deficiency ofatlas. Objective: To highlight the atypical and late presentation of isolated deficiency of lamina of atlas. Summary of background data: Isolated anomalies of atlas are a rare occurrenceand their presentation is variable. In childhood they usually manifest as a torticollis while inadults they can manifest as signs and symptoms of cervical canal stenosis. We report a rarecase of isolated laminar deficiency of atlas which presented with trapezius pain. Methods: Clinical and radiographic details are presented documenting the atypical late presentation. Results: Since the patient was not having neurological signs patient was managed conservativelyand was doing well at one year follow-up. Conclusion: To conclude isolated laminar deficiencyof atlas is an extremely rare condition which usually presents as torticollis or with symptoms ofcanal stenosis but it can also present late as antrapezial pain secondary to occupational stresses of the individual. If patient has neurological signs then early fusion is recommended.

Case History

A 27-year-old man presented to our outpatient clinic with complaints of pain in right trapezius region for the last five days. The patient was a software professional and had been working overtime for the past three weeks. The patient denied any history of trauma. There was no pain in the neck or any radiating pain going down the shoulder or arm. The patient denied any weakness or paresthesiae in the upper/lower limbs, headaches with diurnal variation. A detailed history was taken and it did notreveal any evidence of cervical spine problems in childhood. Family history was negative with regards to cervical spine problems or any other congenital anomalies. The patient had tried massaging his trapezius region without any benefit. A general physical examination was carried out and was found to be normal. Simultaneously a detailed neurological examination was carried out and it did not reveal any abnormality. At this stage examination of cervical spine was done and it revealed an essentially normal exam except that the terminal part of extension was painful. There was no paraspinal spasm/rigidity.

X-rays of the cervical spine (anteroposterior lateral, open mouth odontoid view) wereordered. Anteroposterior view of this cervical spine normal should normal alignmentof the cervical spine (Fig. 1). The lateral view (Fig. 2) revealed an atlantodensinterval of 2.7 mm (within normal limits) and bony deficiency in region of lamina(post arch). The odontoid open mouth view (Fig. 3) revealed the same distance betweenlateral mass of atlas and odontoid on both sides. Flexion and extension films were orderedand they revealed a normal atlantodens interval and no evidence of instability.A neurologist opinion was sought and their examination was also reported as normal. Patient was advised further work-up including magnetic resonance imaging (MRI) of the brain and spine and a 3D CT of the cervical spine. MRI of the brain and spinedid not reveal any evidence of intraspinal anomalies or any brain malformations.There was bilateral deficiency of post arch (lamina) with symmetrical facet joints. Therewas no evidence of cervical canal stenosis. Patient refused to undergo 3D CT scanevaluation because of cost constraints. Patient was advised symptomatic treatmentwith anti-inflammatory (Naproxen) drugs and muscle relaxants (Thiocolchicoside).The acute episode subsided in five days and patient was put in a rehab program to strengthen the scapular stabilizers, paraspinal musculature of cervical spine and the trapezius. Patient was advised to avoid any contact sports.

A neurosurgical opinion was sought and the consensus was that as patient hadbeen asymptomatic till date no surgical intervention was necessary as there was noevidence of cervical canal stenosis. Patient was advised six monthly follow-ups. Patient wasasymptomatic at his one year follow-up.

Discussion

The vertebral column develops around 2-4 weeks of intrauterine life with sclerotome cells arising from paired somites migrating medially and meeting around notochord.

The surrounding paraxial mesoderm becomes segmented into four cranial and eight cervical somites at 2-3 weeks. The sclerotomes form condensed masses which is more prominent at the caudal border with less condensed masses both cephalad and distal to it.

Each somite differentiates into cranial and caudal parts which reunite with caudal and cranial halves, respectively of the adjacent somites forming each provertebra.

The condensed layer migrates cranially to middle of adjacent myotome to give rise to annulus fibrosus of the disc. Caudal portion of each sclerotome fuses with cranial portion of sclerotome which goes on to form primordium of vertebral body.

Thus at birth each vertebral body consists of three bones joined by cartilage and bony union is achieved over years. Depending on the stage of arrest one can have aplasia/hypoplasia of the vertebra. If there is maldevelopment of the facets then one has torticollis of the neck.

The aplastic part of the vertebra is replaced by a fibrous cord which can compromise the cervical canal resulting in symptoms of canal stenosis. There have been very few reported cases of congenital anomalies of the atlas. Dubousset1 has described congenital hemi atlas or hypoplasia of atlas that can cause marked torticollis if left untreated. In majority of the patients the deformity was noted at birth as a lateral translation of the head on the trunk. A detailed work-up (MRI, CT) usually reveals evidence of other intraspinal anomalies such as foramen magnum stenosis and Arnold-Chiari malformations. The usual treatment protocol is use of a halovest to get an acceptable position followed by posterior fusion from occiput to C-2. Hsu et al2 reported neurological symptoms due to congenital cervical spinal stenosis at the atlas level. Congenital atlantal stenosis is usually due to hypoplasia of the posterior arch of the atlas. It is one of the rare causes of spinal stenosis, and only 12 symptomatic patients with isolated atlantal stenosis have been reported. Recommended treatment is surgical decompression, and all reported patients receiving surgical treatment improved to some degree. Phan et al3 reported similar observation on two patients. To the best of our knowledge this is the only reported case of bilateral laminar deficiency with a varied and late presentation. As the patient had been asymptomatic till adult life, a wait and watch policy was adopted. It was emphasized to the patient that he should not indulge in any competitive contact sports.

To conclude, isolated laminar deficiency of atlas is an extremely rare condition which usually presents as torticollis or with symptoms of canal stenosis but it can also present late as an trapezius pain secondary to occupational stresses of the individual.

If patient has neurological signs then early fusion is recommended.

References

1. Dubousset J. Torticollis in children caused by congenital anomalies of the atlas. J Bone Joint Surg Am1986;68(2):178-88.
2. Hsu YH, Huang WC, Liou KD, et al. Cervical spinal stenosis and myelopathy due to atlas hypoplasia.J Chin Med Assoc 2007;70(8):339-44.
3. Phan N, Marras C, Midha R, et al. Cervical myelopathy caused by hypoplasia of the atlas: two case reportsand review of the literature. Neurosurgery 1998;43(3):629-33.