Endoscopic Anterior Cranial Base Resection on Patients with Previous Frontal Sinus Cranialization: Challenging Reconstruction

Objective To review a difficult case of anterior cranial base resection and reconstruction with a history of frontal sinus cranialization, and compare anatomical defect sizes for those with cranialization and review reconstructive options

Background Anterior cranial base surgery for tumor resection has its own innate challenges for surgical access, and subsequent reconstruction. Although frontal sinus cranialization is becoming less common for trauma and infectious management, it continues to be performed when an open approach for tumor resection is required. In these situations, the defect is significantly larger with a defect now measuring to the anterior frontal table. This study measures the expected defect from traditional endoscopic anterior cranial base resection versus expected defect from cranialization, and reviews a related difficult case.

Study Design Anatomical study of CT scans and case report.

Methods CT sinus scans of 50 patients, who had FESS for chronic rhinosinusitis, were analyzed in a period from December 2016 to August 2017. On sagittal views, measurements were performed from the tuberculum to the anterior border of the crista galli for expected anterior-posterior defect during endoscopic anterior cranial base resection. Further measurements were taken to the inner cortex of the anterior frontal table. On axial CT views, measurements were taken at the level of the crista galli from the posterior table to the inner cortex of the anterior table as a surrogate measure for length increase in cases of frontal sinus cranialization. We review these in the setting of our case report.

Illustrative Case Patient with history of previous bifrontal craniotomy with pericranial flap reconstruction for meningioma and postoperative radiation. The patient underwent endoscopic endonasal approach and eyebrow supraorbital craniotomy due to lateral extension of the tumor. Reconstruction was performed with nasoseptal flap, which was not enough to cover the entire defect. A 1-cm anterior gap was reconstructed with Alloderm and fat graft. Patient had postoperative CSF leak which was repaired endoscopically with fat graft. One month later, she had increased headache and CT scan showed extradural pneumocephalus with no obvious leak. Subsequently, she had bifrontal craniotomy and reconstruction of the anterior defect with galeal/frontalis muscle flap with resolution of the pneumocephalus and closure of the defect.

Results Fifty CT scans were reviewed, half were male. Sagittal view measurements from the tuberculum to the anterior crista galli averaged 48.8 mm (SD: 3.6 mm, 95% CI: 47.6–50 mm). Further measurements on sagittal view to the inner cortex of the anterior frontal table were significantly larger (average: 59.3 mm; SD: 5.7 mm). Measurements on the axial view of the posterior frontal table at the crista galli to the inner cortex of the anterior frontal table averaged 11.5 mm (SD: 3.5 mm, 95% CI: 10.4–12.6 mm).

Conclusion CT scan measurements can help predict the expected defect size for a standard patient undergoing anterior cranial base resection versus someone with a history of frontal cranialization. An anterior-posterior defect of 1 cm puts considerable strain on our standard rotational nasoseptal flap reconstruction, and being mindful of these size parameters will aid in successful repair and patient outcomes.