Two patients with proatlas segmentation malformation.

A 58-year-old female and an 18-year-old male patient had progressive spastic quadriparesis of 10 years and 6 months duration, respectively. Proatlas segmentation malformation (PSM) was confirmed using three-dimensional (3D) reconstructive CT scans and MRI. Surgical procedures in one patient involved anterior decompression via a transoropharyngeal approach, cranial traction, and posterior occipital-cervical fixation and fusion. His postoperative neurological status had improved remarkably, with imaging showing good realignment of the occipito-atlanto-axial complex with comfortable decompression of the cervico-medulla junction and relief of syringomyelia. MRI and 3D-CT scans are the definitive diagnostic tools for PSM, and appropriate aggressive surgical intervention should be undertaken.