title: Muscle Insertion Line as a Simple Landmark To Identify the Transverse Sinus When Neuronavigation Is Unavailable.
abstract: OBJECTIVE
  Skull opening in occipital and suboccipital regions might be associated with risk of damage to the transverse venous sinus and the confluence of sinuses. We analyze the value of magnetic resonance (MR) imaging in localizing the venous sinuses in relation to the superior muscle insertion line (MIL) on the occipital bone.
  
  
  METHODS
  We retrospectively analyzed head MR images of 100 consecutive patients imaged for any reason from 1 January 2013. All MR images were interpreted by a radiologist (R.K.). The superior MIL was identified at the midline and on both midpupillar lines, which represent the most frequent sites of skin incision and craniotomy (median and lateral suboccipital craniotomy, respectively).
  
  
  RESULTS
  Patients comprised 56 women (56%) and 44 men (44%). Their mean age was 54 (range 18-84) years. The muscles of the posterior skull were readily visible and clearly identified in both T1 and T2 images of all patients. Identification of the insertion zone and its relation to the venous structures was most readily made in the sagittal plane.
  
  
  CONCLUSIONS
  We found that the upper muscle insertion line on occipital bone corresponds to the underlying venous sinus and can be used as a reliable anatomic landmark. We identified it in 100% of preoperative MR images of heads with an intact occiput.
authors.affiliation: Department of Neurosurgery, Turku University Central Hospital, Turku, Finland. Electronic address: j.v.kivelev@gmail.com.
authors.forename: Juri
authors.initials: J
authors.lastname: Kivelev
authors.affiliation: Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: Riku
authors.initials: R
authors.lastname: Kivisaari
authors.affiliation: Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: Mika
authors.initials: M
authors.lastname: Niemelä
authors.affiliation: Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: Juha
authors.initials: J
authors.lastname: Hernesniemi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059925:Anatomic Landmarks / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D038361:Neuronavigation; D009777:Occipital Bone / Q000033:anatomy & histology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D054064:Transverse Sinuses / Q000033:anatomy & histology*; D055815:Young Adult
keywords: Muscle insertion; Posterior craniotomy; Venous sinuses