title: A new landmark for finding the sigmoid sinus in suboccipital craniotomies.
abstract: BACKGROUND
  The suboccipital craniotomy is one of the most commonly performed neurosurgical approaches.
  
  
  OBJECTIVE
  To define a new cranial landmark, the digastric point, located at the top of the mastoid notch in the mastoid portion of the temporal bone that may assist surgeons performing this craniotomy and to study the relationships between this point and other surface landmarks.
  
  
  METHODS
  Craniometric measures were taken from 127 dry human adult skulls (90 male and 37 female). The measures were taken in millimeters by a digital caliper. Transillumination of the skull with laser or light-emitting diode was used to assess the correspondence of the digastric point in the inner surface of the skull.
  
  
  RESULTS
  The mean distance between the digastric point and the sigmoid sulcus in 254 measures was 3.10 mm (SD, 3.11 mm). The digastric point was over the sulcus of the sigmoid sinus in 49.6% of the cases on the right side and in 29.9% of the cases on the left side. The distance between the jugular point and the stylomastoid foramen was smaller on the right side (mean, 8.89 mm; SD, 2.61 mm; P = .041). Comparing genders regardless of side, the distances between the digastric and jugular points and from the jugular point to the stylomastoid foramen were smaller in female skulls (P = .000 and .006, respectively).
  
  
  CONCLUSIONS
  The digastric point may be a useful landmark to expose the sigmoid sinus during suboccipital approaches.
authors.affiliation: Universidade Federal de Minas Gerais and Instituto Mineiro de Neurocirurgia, Belo Horizonte, Minas Gerais, Brazil. jraso@uol.com.br
authors.forename: Jair Leopoldo
authors.initials: JL
authors.lastname: Raso
authors.forename: Segastião Nataniel Silva
authors.initials: SN
authors.lastname: Gusmão
mesh_terms: D000328:Adult; D003392:Cranial Sinuses / Q000601:surgery*; D003399:Craniotomy / Q000379:methods* / Q000592:standards*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009777:Occipital Bone / Q000033:anatomy & histology* / Q000601:surgery*; D015203:Reproducibility of Results; D055815:Young Adult