Midline as a landmark for the position of the superior sagittal sinus on the cranial vault: An anatomical and imaging study.
BACKGROUND
Craniotomies involving the midline are regular practice in neurosurgery, during which injury to the superior sagittal sinus (SSS), an uncommon yet devastating event, may occur. The midline tends to be the most common landmark used to identify the position of the SSS. In this study we examined the reliability of the midline as a landmark for the SSS.


METHODS
We performed bilateral craniectomies on eight cadaveric heads, preserving the coronal, sagittal, and lambdoid sutures. The width of the SSS and its displacement from midline were measured on the cadaveric specimens and on 105 normal magnetic resonance images (MRIs) of the head at the following locations: halfway between nasion and bregma (NB), bregma (B), halfway between bregma and lambda (BL), lambda (L), and inion (I).


RESULTS
In all cadaveric specimens, the SSS was partially or totally displaced toward one side of midline, usually to the right. It tended to be closer to midline in the frontal region and more displaced posteriorly. The SSS usually drained into the right-side transverse sinus. The mean width of the SSS was 4.3, 5.9, 6.9, 7.9, and 7.8 mm, and the average displacement from midline was 4.3, 6.3, 5.5, 6.9, and 6.0 mm for NB, B, BL, L, and I, respectively. These measurements were then compared with those obtained from the MRIs.


CONCLUSIONS
The SSS was consistently displaced on either side of midline. Thus, the midline is not reliable for identifying the SSS, and caution should be used within 6-10 mm on either side of midline.
Departamento de Neurocirurgia, Hospital Mater Dei, Belo Horizonte, Brazil.
Cassius Vinicius C
CV
Reis
Departamento de Neurocirurgia, Federal University of Minas Gerais, Belo Horizonte, Brazil.
Sebastião N S
SN
Gusmão
Division of Neurological Surgery and Department of Neurosurgery Research, Barrow Neurological Institute, Phoenix, Arizona, USA.
Ali M
AM
Elhadi
Division of Neurological Surgery and Department of Neurosurgery Research, Barrow Neurological Institute, Phoenix, Arizona, USA.
Alexander
A
Dru
Departamento de Neurocirurgia, Hospital Mater Dei, Belo Horizonte, Brazil.
Uédson
U
Tazinaffo
Division of Neurological Surgery and Department of Neurosurgery Research, Barrow Neurological Institute, Phoenix, Arizona, USA.
Joseph M
JM
Zabramski
Division of Neurological Surgery and Department of Neurosurgery Research, Barrow Neurological Institute, Phoenix, Arizona, USA.
Robert F
RF
Spetzler
Division of Neurological Surgery and Department of Neurosurgery Research, Barrow Neurological Institute, Phoenix, Arizona, USA.
Mark C
MC
Preul
Confluence of sinuses; sagittal suture; superior sagittal sinus; torcular Herophili