Anatomical landmarks to locate the junction between transverse and sigmoid sinuses in translabyrinthine and retrosigmoid open surgical approaches

Abstract

Introduction Hematoma due to dural-sinus damage is a known complication when introducing burr holes in open transcranial surgery. Our objective was to identify safe areas to avoid dural-sinus damage based on anatomical landmarks in translabyrinthine and retrosigmoid open surgical approaches where neuronavigation facilities are not available. Methods A descriptive anatomical study was conducted on adult skulls. Distances to transverse and sigmoid sinuses on either side were measured using fixed anatomical landmarks: asterion, inion, margins of suprameatal triangle and superior nuchal line. Measurements were standardized according to the cranial indices (cranial index=anteroposterior diameter/transverse diameter) of each skull. Results Thirty-two adult skulls (male:female=22:10) were studied. Mean cranial index, width of transverse and sigmoid sinuses were 0.785±0.045, 9.1±2.3mm and 9.7±1.2mm respectively. Mean vertical distances from asterion and inion to the transverse sinus were 1.1±3.4mm and 14.7±5.9mm respectively. Posterior border of the sigmoid sinus was located 14.7±5.9mm, and 59.9±7.4mm anterior to asterion and inion respectively. t-tests did not show significant differences of these distances on either sides (p>.05). Pearson's correlations were insignificant between the measurements and the cranial indices (p>.05). Measurements from the suprameatal triangle to the dural-sinuses had the minimum variance. In >95% of the times the sigmoid sinus was located ≤23 mm posterior and ≤7 mm superior to the suprameatal triangle. Discussion and conclusions Suprameatal triangle was a consistent surface landmark to locate dural-sinuses. Dural-sinus damage could be avoided in 95% of the times by placing burr hole at least 7mm superior and 23 mm posterior to the suprameatal triangle.

The Asterion-to-Transverse Process of the Atlas Line as a Surgical Landmark

“…In many developing countries, neuronavigation is not available, and surgery is planned solely based on patient's anatomy. 22 While the A-TPC1 line does not contribute to placing the key burr hole in the retrosigmoid craniotomy at the TSJ, it is helpful in predicting the distal trajectory of the sigmoid sinus, allowing for more "educated" drilling 13 From mastoid notch to the squamosal suture Lateral to transverse-sigmoid junction 91.5% lateral to transversesigmoid junction Squamosal-parietomastoid suture junction 11,12 Squamosal-parietomastoid suture junction…”

“…In many developing countries, neuronavigation is not available, and surgery is planned solely based on patient's anatomy. 22 While the A-TPC1 line does not contribute to placing the key burr hole in the retrosigmoid craniotomy at the TSJ, it is helpful in predicting the distal trajectory of the sigmoid sinus, allowing for more "educated" drilling Between the asterion and the lateral aspect of the transverse process of the atlas Posterior to the sigmoid sinus/jugular vein 100% posterior to the sinus, closest at digastric point during its exposure. This has special implications for the "extended" or trans-mastoid retrosigmoid approach, 23 where the sigmoid sinus is exposed then gently retracted with dural sutures to maximize the retrosigmoid corridor.…”

Computed Tomography Study of the Retrosigmoid Craniotomy Keyhole Approach Using Surface Landmarks

“…While other skull-surface landmarks are also used to locate the transverse-sigmoid junction, they have anatomic variations, and some are too far from the surgical incision to be practical for surgical use [12]. Tree-dimensional (3D) computed tomography (CT) image-guided surgery allows for correct craniotomy placement but is not applicable in hospitals lacking the necessary equipment or for patients with contrast hypersensitivity, nor is it practical in emergency surgery [13]. However, an anatomical study of surface landmarks and their relationship with the transverse-sigmoid junction can provide relevant information regarding accurate retrosigmoid craniotomy placement without image guidance.…”

Morphometric evaluation and quantification using Fiji

“…A myriad of studies in gross anatomy, radiological anatomy and developmental biology utilize measurements such as distance, angle, area, volume and curvature to describe morphology of different structures. The classical approach of obtaining these measurements was to use instruments such as calipers (1), measuring tapes (2), set squares (3) and goniometers (4). Often magnifying glasses were used to aid measurements since fine structures could not be accurately resolved by the naked eye (5).…”