New Approach—Biportal Endoscopic Transfrontal Sinus Approach: A Novel Minimally Invasive Approach to the Anterior Cranial Fossa: Cadaveric Feasibility Study

Introduction: The transglabellar approach has been described as a direct access to the anterior cranial fossa and an alternative to the bifrontal craniotomy in certain cases. However, the incision in the nasion can be cosmetically undesirable. In this study we propose to transfer the concept of endoscopic endonasal (EEA) transsphenoidal surgery to the frontal sinus. This new minimally invasive approach, the biportal endoscopic transfrontal sinus (BETS) approach has the potential to avoid the complications associated with the bifrontal craniotomy and provide a more central access compared to the supraorbital approach, minimizing the aesthetic impact on the patient.

Methods: Four formalin specimens were used for this study. Incisions were made over both eyebrows from the supraorbital notch to the medial end of the eyebrow. The subgaleal plane below the forehead was then dissected through these incisions with the aid of the endoscope. A periosteal flap was harvested and pedicled toward one of the incisions. A craniotomy of the external table of the frontal sinus over the frontal sinus was performed. The mucosa was removed, and all the septa were drilled for subsequent cranialization. A craniotomy was performed including the posterior table of the frontal sinus. Dura mater was opened at the basal level parallel to the anterior cranial fossa bilaterally. The superior sagittal sinus along with falx were divided immediately superior to the crista galli. Dural reconstruction was performed with fat graft, pediculated periosteal flap and fibrin glue. Bone flap replacement was performed with titanium plates and filling of the external table defect with bone cement. After the approach, the integrity of the supraorbital vasculonervous bundle was verified in all specimens.

Results: Intradurally, like in EEA, this approach allows working with the endoscope and suction through one of the incisions and an instrument in the other. The approach allows access to the whole anterior cranial fossa, subfrontal, and interhemispheric corridors, all the way up to the suprachiasmatic corridor and through the lamina terminalis to the third ventricle. It also permits extension in the coronal plane up to both Sylvian fissures.

Discussion: This novel approach provides direct access to the anterior fossa, allows sectioning of the sagittal sinus just above the crista galli, minimizes the level of frontal lobe retraction, and provides potentially less tissue disruption and improved cosmesis. The size and morphology of the frontal sinus impacts the operation, being small sinuses more challenging. The superior extension of the approach is determined by the height of the frontal sinus. CSF fistula risk remains as one of the bigger concerns due to the narrow corridor that make it difficult for a watertight closure. However, this risk can be minimized with a pedicled flap as in EEA. Mucocele risk is minimized with full cranialization of the frontal sinus.

Conclusion: BETS approach is a minimally invasive approach that translates the concepts of EEA to the frontal sinus. It allows excellent access to the anterior cranial fossa structures with minimal frontal lobe retraction.

Publication History

Article published online:
05 February 2024