Unilateral lateral mass hypertrophy: An extremely rare congenital anomaly of atlas
The present case report is about a 28-year-old female patient who presented with posterior cervical pain of 2 years duration along with ascending spastic quadriparesis for 1 year. On examination, she had subtle quadriparesis (power 4/5 on the right upper and lower limbs with 4+/5 power on the left side). Deep tendon reflexes were uniformly exaggerated and plantars were bilaterally up going. There was graded sensory impairment below C4 dermatome (30-50%) and posterior column impairment was noted in upper and lower limbs. She had left sided torticollis and neck movements, particularly rotation, were restricted toward the right side. There were no lower cranial nerve dysfunction and no stigmata pertaining to the CVJ anomalies were found on general examination.\nShe was investigated with computed tomography (CT) scan and magnetic resonance imaging (MRI) of the CVJ. On CT scan, there was hypertrophy involving the right lateral mass of atlas causing impingement into the bony cervical canal and consequent narrowing of the transverse canal diameter. The bony overgrowth was similar in density as the rest of the C1 ring. Posterior arch of C1 was hypoplastic and left hemi-arch was absent. There was no evidence of atlanto axial dislocation or basilar invagination [Figure –]. MRI of this area showed compression of the spinal cord from right lateral aspect with distortion of the cord. Cerebellar tonsils were seen impacted at the foramen magnum with obliteration of the cistern magna. The tonsilar descent was seen up to the level of C1. There was T2 hyperintensity inside the substance of the cord at the level of C2 body [Figure and ].\nAs the patient had both lateral and posterior compression on the spinal cord, we performed transoral decompression of the hypertrophied lateral mass followed by removal of posterior lip of foramen magnum, excision of hypoplastic posterior arch of atlas and occipito-cervical (C2) fusion with titanium cable. The histopathological examination of the hypertrophied lateral mass revealed the presence of fibro-osseous tissue and no evidence of malignancy was found.\nPost-operatively, the patient had relief of the neck pain and reduction in severity of spasticity. Post-operative reconstructed CT of CVJ revealed adequate bony decompression and the posterior construct in situ [Figure –]. The patient had an uneventful post-operative period and was discharged in stable condition. At the time of writing this report, she had completed 12 months follow-up and she had complete recovery of power in her limbs.