2025 Proffered Presentations
S345: MEASUREMENTS OF THE FRONTAL SINUS IN CORRELATION TO TRANS FRONTAL SINUS KEYHOLE APPROACHES TO THE ANTERIOR SKULL BASE
Miguel Saez-Alegre, MD, PhD; Antonio Bon Nieves, BS; Lazaro Peraza, MD; Carlos Pinheiro Neto, MD, PhD; Mayo Clinic, Rochester, MN, USA
Background: The frontal sinus, due to its anatomical position, has gained interest as a minimally invasive pathway for neurosurgery, with a number of trans-frontal sinus keyhole (TFSK) approaches been described. However, the variability in the size of the frontal sinus necessitates a thorough study of the feasibility of TFSK approaches. The goal of this study was to assess the feasibility of various TFSK approaches to the anterior skull base by measuring frontal sinus dimensions.
Methods: We conducted a retrospective analysis of 108 high-quality CT scans from patients without head and neck pathology. The dimensions of the frontal sinuses were measured using area contouring and linear measurements. We assessed the height, width, and area of the frontal sinus in the coronal plane. Approaches were categorized into lateral and midline TFSK, based on whether one or both frontal sinuses were used. A keyhole craniotomy was defined as an area of at least 2x2 cm (4 cm²). Lateral TFSK approaches were defined as feasible if the lateral frontal sinus had an area greater than 4cm2 (2x2cm). Midline TFSK approaches were defined as feasible if the total area of the frontal sinus was greater than 4cm2.
Results: Among the 108 patients, 94.44% had at least one frontal sinus present, with 42.59% having a sinus large enough for a right or left lateral TFSK approach (≥4 cm²). For midline TFSK, 77.78% of patients had a frontal sinus large enough. Notably, 14.68% of patients exhibited either unilateral or bilateral frontal sinus absence.
The mean frontal sinus area was 4.04 ± 2.21 cm² on the right and 4.33 ± 2.39 cm² on the left. There was no significant difference between the sizes of the right and left frontal sinuses (p = 0.37).
Discussion: The variability in the size and pneumatization of the frontal sinus presents both opportunities and challenges for TFSK surgery. Our study shows that while most patients have sufficient sinus size for midline approaches, a notable percentage (14.68%) lack sufficient pneumatization for any TFSK approach. The definition of a keyhole craniotomy as 2x2 cm (4 cm²) provides a useful threshold, but further research is needed to optimize this definition and evaluate outcomes based on varying sinus sizes.
Conclusions: Trans-frontal sinus keyhole surgery represents a viable option for accessing the anterior skull base in a majority of patients, especially those with adequately pneumatized frontal sinuses. However, variations in sinus size and anatomy necessitate tailored approaches. Our findings show that lateral TFSK approaches are feasible in 42.59% of patients, and midline approaches are feasible in 77.78%.
Violin plot of the measurements of the frontal sinus showing the area of the left and right frontal sinuses
Image #1: CT measurements of the frontal sinus in the coronal view. The horizontal A line corresponds to the width, the vertical B line corresponds to the height, and the C corresponds to the contour of the sinus.