Unilateral lateral mass hypertrophy: An extremely rare congenital anomaly of atlas.

A wide variety of congenital anomalies are observed around the craniovertebral junctional area. However, hypertrophied unilateral lateral mass of atlas in association with chiari-1 malformation leading to myelopathy is extremely uncommon. Herein we report a case of 28-year-old female who presented to us with a high cervical compressive myelopathy. Imaging revealed bony hypertrophy involving right sided C1 lateral mass along with chiari malformation-type 1. She underwent transoral as well as posterior decompression followed by occipito-cervical fusion. The authors discuss their case in light of other such reported cases and present a review of the literature.