Frontal lobe position after single-layer cadaveric dermal matrix repair of large anterior skull base defects

Objective:Endoscopic repair of large anterior skull base(ASB)defects has excellent results when using multilayered repairs with a nasoseptal flap.However,in extensive intranasal tumors,a nasoseptal flap may not always be available.One alternative option is a flexible single-layer ASB repair.Initial studies indicate low cerebrospinal fluid leak rates with a single-layer repair.However,the level of frontal lobe support,particularly the propensity for a significant inferior displacement of the frontal lobe,is not known.The goal of this study is to determine the frontal lobe position after single-layer acellular dermal allograft repair in large ASB defects.Study Design:Retrospective cohort study.Setting:Tertiary care medical center.Subjects and Methods:This cohort study compares the frontal lobe position in adults who underwent endoscopic endonasal ASB tumor resection and single-layer cadaveric dermal matrix repair(ASB cohort)with control subjects without intracranial abnormalities(control cohort).The ASB cohort includes subjects with an ASB defect of≥5 cm anterior/posterior and≥1.5 cm wide and who had imaging at least 2 months after surgery.The frontal lobe position is measured on sagittal CT/MRI using a reference line from the base of the sella to the nasion.A value of zero indicates that the inferior-most aspect of the frontal lobe is at the level of the nasion-sellar line.A positive value indicates that the frontal lobe is inferior to the nasion-sellar line.The ASB cohort frontal lobe position is compared with the control cohort using the Mann-WhitneyU test.A priori we set an absolute difference of 5 mm as a clinically significant difference.Results:The ASB cohort includes 47 subjects who are 57%male with an average age of 60 years(range:31-89 years).The most common ASB pathology is esthesioneuroblastoma(n=21)and 81%of the ASB cohort had postoperative radiation.The control cohort includes 20 subjects who are 60%male,with a mean age of 45 years(range:19-74 years).The majority of controls underwent imaging for head trauma(n=13).The ASB mean frontal lobe position is-0.2 mm superior to the nasion-sellar line(range:-9.2 to 10.4 mm),while the control’’s mean frontal lobe position is 1.1 mm inferior to the nasion-sellar line.This difference is not statistically significant(P=0.13)and does not reach our a priori definition of clinical significance.The frontal lobe position of ASB subjects who had radiation is closer to the nasion-sellar line as compared with those who did not undergo radiation.Conclusions:Single-layer acellular dermal graft repair maintains frontal lobe support and position in large ASB defects.