title: Proatlas segmentation anomalies: Surgical management of five cases and review of the literature.
abstract: OBJECTIVE
  Proatlas segementation anomalies are due to defective re-segmentation of the proatlas sclerotome. These anomalies of the craniovertebral junction are rare and have multiple presentations. The aim of this study is to report this author's personal experience in managing five of these patients with different radiological findings necessitating different surgical strategies and to provide a brief review of the relevant literature.
  
  
  METHODS
  Five patients, all in the second decade of life were treated between 2010 and 2013. There were three males and two females. All the patients presented with spastic quadriparesis and/or cerebellar signs. Patients underwent plain radiographs, MRI and CT of the craniovertebral junction. CT of the cranioveretebral junction was the key to the diagnosis of this anomaly. Postoperatively, patients were assessed with plain radiographs and CT in all patients and MRI in one.
  
  
  RESULTS
  Two patients underwent craniovertebral realignment with occipitocervical fixation, two patients underwent C1-C2 fixation using Goel-Harms technique and one patient underwent craniovertebral realignment with C1-C2 fixation using spacers in the atlanatoaxial joint and foramen magnum decompression. All patients improved during follow up.
  
  
  CONCLUSIONS
  Proatlas segmentation defects are rare anomalies of the craniovertebral junction. Routine use of thin section CT of the craniovertebral junction and an awareness of this entity and its multivarious presentations are necessary for clinicians dealing with abnormalities of the craniovertebral junction.
authors.affiliation: Department of Neurosurgery, Madurai Medical College, Madurai, Tamil Nadu, India.
authors.forename: Natarajan
authors.initials: N
authors.lastname: Muthukumar
keywords: Assimilation of atlas; C1 lateral mass screw; C2 pars screw; atlanto-axial subluxation; basilar invagination; congenital malformations; craniovertebral junction; occipito-cervical fusion; proatlas segmentation anomaly