title: Usefulness of the contralateral Omega sign for the topographic location of lesions in and around the central sulcus.
abstract: BACKGROUND
  The central sulcus may be located through magnetic resonance imaging (MRI) by identifying the ipsilateral inverted Omega shape. In a brain with a lesion in this area, its identification becomes a hard task irrespective of the technique applied. The aim of this study is to show the usefulness of the contralateral Omega sign for the location of tumors in and around the central sulcus. We do not intend to replace modern techniques, but to show an easy, cheap and relatively effective way to recognize the relationship between the central sulcus and the lesion.
  
  
  METHODS
  From July 2005 through December 2010, 43 patients with lesions in and around the central sulcus were operated using the contralateral Omega sign concept. Additionally, 5 formalin-fixed brains (10 hemispheres) were studied to clarify the anatomy of the central sulcus where the Omega shape is found.
  
  
  RESULTS
  The central sulcus has three genua. The middle genu is characterized by an inverted Omega-shaped area in axial sections known as the Omega sign. On anatomical specimens, Omega was 11.2 ± 3.35 mm in height, on average, and 18.7 ± 2.49 mm in width, at the base. The average distance from the medial limit of the Omega to the medial edge of the hemisphere was 24.5 ± 5.35 mm. Identification of the Omega sign allowed for the topographic localization of the contralateral central sulcus in all our surgical cases but one.
  
  
  CONCLUSIONS
  The contralateral Omega sign can be easily and reliably used to clarify the topographic location of the pathology. Hence, it gives a quick preoperative idea of the relationships between the lesion and the pre- and post-central gyri.
authors.affiliation: Department of Neurosurgery, Hospital Padilla, Tucumán, Argentina.
authors.forename: Alvaro
authors.initials: A
authors.lastname: Campero
authors.forename: Pablo
authors.initials: P
authors.lastname: Ajler
authors.forename: Carolina
authors.initials: C
authors.lastname: Martins
authors.forename: Juan
authors.initials: J
authors.lastname: Emmerich
authors.forename: Luiz Felipe
authors.initials: LF
authors.lastname: de Alencastro
authors.forename: Albert
authors.initials: A
authors.lastname: Rhoton