Mucosal Epithelial Preservation of Free Nasal Grafts Depending on the Recipient Site.

OBJECTIVES/HYPOTHESIS: Reconstruction of mucosal defects using free mucosal grafts has become a common procedure during endoscopic sinus surgery. Epithelialization of mucosal grafts affects postoperative complications and outcomes, which could be influenced by different recipient tissue. However, morphological changes occurring in the grafts transplanted over different tissues remain unexplored. STUDY DESIGN: An animal study. METHODS: Free mucoperichondrial grafts were prepared from the nasal septum of rabbits; the cartilage group had reconstruction on the nasal septal cartilage, and the perichondrium group had reconstruction on the contralateral perichondrium. The nasal septum was removed after 1 and 4 weeks of reconstruction, and the graft was histologically evaluated. RESULTS: After 1 week of reconstruction, the mucosal epithelium of grafts in the cartilage group disappeared, whereas the columnar epithelium of grafts was preserved in the perichondrium group. After 4 weeks of reconstruction, the mucosal defect site was covered with mucosal epithelium in both groups. However, while squamous epithelium was mostly observed in the cartilage group, columnar epithelium containing the healthy ciliary and goblet cells was observed in the perichondrium group. Statistically significant differences were detected in the parameters of epithelial morphology between the two groups, which were higher in the perichondrium group. CONCLUSIONS: In the reconstruction of mucosal defects using free mucosal grafts, difference in recipient tissue affects the graft epithelial morphology. LEVEL OF EVIDENCE: NA Laryngoscope, 132:2301-2306, 2022.

Frontal Sinus "Hump": An Anatomical Risk Factor for Anterior Skull Base Injury in the Endoscopic Modified Lothrop Approach (Outside-In Frontal Drill-Out).

Skull base injuries caused by the outside-in frontal drill-out technique have not been reported. In this report, we chose an outside-in approach to open the frontal sinus for olfactory neuroblastoma resection. Although we identified the first olfactory fibre, the anterior skull base was damaged while drilling into the frontal sinus on the tumour side. We reconstructed the skull base in multiple layers using fascia and cartilage. Postoperative cerebrospinal fluid leakage or intracranial haemorrhage was not observed. In this case, a morphological difference existed in the posterior wall of the frontal sinus between the right and left sides, like a "hump" in the posterior wall of the frontal sinus. This case of damage to the anterior skull base that could not be avoided by identifying the first olfactory fibre alone is the first published case of skull base injury caused by the outside-in approach due to morphological variations of the frontal sinus and skull base. In this approach, the posterior wall of the frontal sinus cannot be observed because the intraoperative landmark is limited to the first olfactory fibre. Therefore, morphological variations of the posterior wall of the frontal sinus should be analysed in advance to prevent cranial base injury.