The management of patients with SWMs has evolved over the past decades, resulting in minimal morbidity and a satisfactory surgical mortality rate of ~4%.39
After gross total resection, almost all of the larger series with a minimum 5-year follow-up report a 5 to 10% recurrence rate. Subtotal resection, however, has at times been reported to increase the recurrence rate to as high as 60%, while in other cases it has appeared to facilitate growth arrest of the tumor.12,40,41
Our review found an overall mortality rate of 2% and recurrence rates of 13 and 5% for patients undergoing partial versus complete resection, respectively. Additionally, we found that the recurrence rate in Simpson Grade IV patients was 24% (8 of 34 patients). Interestingly, although we noted an increase in recurrence rate in incompletely versus completely resected SWMs, it was not statistically significant. This leads to the question: Does the benefit of completely resecting the remaining tumor outweigh the risk? Initially, we anticipated that a greater extent of resection would be associated with higher morbidity. However, we found this to be untrue. Patients undergoing incomplete resection (Simpson Grade II, III, IV) actually have a higher rate of morbidity than those whose tumors were completely removed (Simpson Grade I).
We hypothesized that tumor location and invasion, rather than extent of resection, caused increase risk of morbidity. Unfortunately, because SWM location and World Health Organization categorization were insufficiently reported, we were unable to fully analyze this hypothesis. In support of our hypothesis, invasion of cavernous sinus when noted in the literature and has been widely associated with high postoperative morbidity. In our view, this is an adequate approximation of overall tumor invasiveness. Upon review and analysis, we noted a significant elevation in cranial nerve III palsy (from 0 to 14%) in patients with cavernous sinus invasion compared with those without. There was also a notable increase in postoperative diplopia, although it did not meet our threshold for statistical significance. These results are no doubt due to the anatomical proximity of cranial nerves III, IV, and VI within the walls of substance of the cavernous sinus. These nerves are likely to already be compromised prior to surgery, and, with cavernous sinus invasion, require minimal disruption to cause marked postoperative morbidity. Therefore, patients with cavernous sinus invasions should be counseled about this risk associated with surgery, irrespective of the surgeon’s preference for complete or incomplete tumor resection. There were no changes in visual acuity in patients with or without cavernous sinus invasion.
In the subgroups (cavernous sinus invasion versus no invasion), there was an unequal distribution of Simpson Grade resections. The distribution showed higher rate of Grade I and II resection without cavernous sinus invasion and a higher rate of Grade III and IV resection with cavernous sinus invasion. This result is not unexpected, due to the known operative difficulty of tumor resection within the cavernous sinus. In the studies reviewed, there was limited data available on the value of radiation therapy as an adjuvant treatment. Future studies should explore the role of postoperative radiation therapy in controlling recurrence.
The observation that the deficits increase in patients who have cavernous sinus invasion can also be attributed to the likelihood that these patients are usually patients with advanced disease. Tumor size, although not statistically significant, is increased in both incompletely resected patients and patients with cavernous sinus invasions. We did not attempt to classify the extent of cavernous sinus involvement by compartment or volume, and this may be a limit of our review. The difficulty with removing tumor from the lateral wall is much different than removing tumor from the contents of the sinus between nerves and the carotid artery. On the other hand, large tumors of the sphenoid wing with diffuse attachments are much more difficult to manipulate surgically and even more difficult to achieve complete removal. The difficulty of the surgical maneuvers required for these tumors is reflected in our series in that it does confirm that cranial nerve deficits continue to be the leading surgical morbidity among patients surgically treated for sphenoid ridge meningiomas.
Consequently, the recent trend in the management of these patients has targeted near complete excision of the tumor with conservation of cranial nerve function, reserving reoperation or adjuvant treatments with radiotherapy or radiosurgery for recurrence. Based on our data, we can argue that preservation of cranial function is more important for satisfactory patient outcomes, as extent of resection is not as strongly correlated to recurrence as previously thought. In addition, the finding of cavernous sinus invasion should be considered a risk to postoperatively ocular motor morbidity, independent of the intention of extent of resection. Consideration of ocular motor morbidity must always be a priority when treating these patients surgically because even in cases where surgical intervention has been contraindicated (e.g., due to advance age), these patients survive for a rather lengthy period of time, from 5 to 22 years, but a major disability is the loss of normal eye movement.18
There are several studies in the literature that focus on visual acuity outcome of patients undergoing surgical intervention for sphenoid ridge meningioma, and surgical measures taken to avoid this significant morbidity. For instance, one study done by Lee et al42
demonstrated that extradural bony decompression of the superior orbital fissure, optic canal and anterior followed by sectioning of the falciform ligament, all before tumor resection produced an improvement in preoperative vision in 75% of the patients. Another study conducted by Russell et al30
adds that although minimizing the indirect compression of optic nerve by releasing it from against the falciform ligament during tumor resection attributes to good visual outcome, but careful surgical manipulation and strict preservation of all vessels feeding the optic structures is equally if not more germane to positive visual outcome. An investigation into decompression and minimizing disruption of the cavernous sinus and the ocular motor cranial nerves would be as useful information as those stated above, which focus primarily on the optic nerve manipulation.