Impact of Dural and Olfactory Nerve Resection on Sinonasal Malignancies with Skull Base Encroachment

Background: The treatment of sinonasal malignancies with anterior cranial base encroachment but without obvious dural invasion varies by institution and surgeon. The need to resect the bony skull base and dura often varies depending on the histopathology, patient functional status, and surgeon preference. Surgeons must balance the risk of microscopic residual disease with the risk of cerebrospinal fluid leak and potential neurologic sequelae. Pre-operative imaging with CT or MRI may predict the extent of invasion, but in cases where the dura is not clearly invaded, there is still uncertainty about the extent of resection.

Methods: We performed a retrospective review of patients with nasal cavity or paranasal sinus malignancies treated surgically at University Health Network in Toronto between 2001 and 2014. Patients were included if they had cribriform plate or fovea ethmoidalis encroachment or erosion without any signs of dural invasion on CT or MRI, as determined by a head and neck radiologist. Relevant prognostic features related to demographics, treatment, tumor extent and histopathology were collected. Rates of occult dural invasion in those undergoing dural resection were reported as were dural recurrence rates in patients who underwent dural resection versus those who did not. Survival analyses were completed using Kaplan-Meier methods.

Results: Thirty-nine patients (mean age 55.5 years; SD 13.8; 54% male) met our inclusion criteria. Fourteen patients (36%) had esthesioneuroblastoma, six patients (15%) had squamous cell carcinoma and the remaining 19 patients (49%) had other malignancies. Twenty-three patients (59%) had dural resections, of whom only 14 patients (61%) had reporting of whether or not dura was invaded. Of those 14 patients, 7 patients (50%) had dural invasion. Five patients had dural recurrences, two with dural resections (9%), and three (19%) without dural resections. There were no differences in five year dural control, loco-regional control and disease specific survival in the dural resection and no dural resection groups (94% vs 86%, p = 0.25; 84% vs 86%, p = 0.49, 87% vs 68%, p = 0.91).

Conclusions: Sinonasal malignancies that encroach the bony anterior skull base, but without overt dural invasion require surgical extirpation with margin control. The risk of microscopic disease of the dura is not clear. This study provides some preliminary evidence that there may be occult dural involvement despite no overt imaging evidence. Dural resection, however, does not seem to be associated with any survival advantage. A surgeon must balance this risk with the added morbidity of dural resection and possible cerebrospinal fluid leak in determining the extent of resection.