Planned Subtotal Resection Followed by GKR for Complex Skull Base Meningiomas: Lausanne Experience

Objective: We retrospectively reviewed all patients operated for skull base meningiomas, who benefited from a combined approach (planned subtotal surgery followed by Gamma Knife surgery (GKS) on the remnant tumor). We focused on clinical outcome and oncological control.

Methods: All cases treated by this approach, between 2010 to 2016, operated by the senior neurosurgeon (R.D.) in Lausanne University Hospital.

Results: From 103 patients were operated for a skull base meningioma, 11 fitted the selection criteria, median age 58 years (44–88). Median follow-up was 25 months (1–49 months). Tumor locations were: petroclival (55%), clinoidal region (18%), spheno-orbital (9%) and cerebello-pontine angle (18%). Clinical presentation was as follows: visual impairment (28%), diplopia (18%), hypoacusia (28%), gait impairment (18%), low cranial nerve disturbances (9%). Multi-staged surgery (multiple surgical approaches: cranaial and/or endonasal) was used in 3 cases. Ten cases resulted in WHO grade I and one in WHO grade II. Six patients (55%) were stable or improved considering with respect to their preoperative status, 2 (18%) experienced visual improvement but developed a mild ophthalmoparesis, 3 (27%) worsened. The mean dose delivered by GKS was 12.4 Gy (median 12, 12–14 Gy) at the 50% isodose line. The mean target volume was 5.14 cc (1.7–7.6 cc) and mean prescription isodose volume 5.75 cc (2.3–9.04 cc). Volume-staged GKS was necessary in 4 cases. Clinical adverse radiation effects were noted in one patient, who developed trigeminal pain and trigeminal hypoesthesia, 6 months after GKS, due to perilesional edema, currently under corticosteroid. After a median follow-up of 25 months (6–49 months) after GKS, available for 10 patients, 60% of tumors regressed in size and 40% remained stable.

Conclusion: Skull base meningiomas requiring combined treatment are challenging lesions, with non-neglectable morbidity. Performing planned subtotal resection to make GKS possible seems to be a valid strategy to achieve local control while limiting neurological morbidity. Surgical chiasmopexy proofed to be very useful in those cases with residual tumor close to optic pathways, to limit the radiation dose received by the former. In cases when single fraction GKS is not suitable, hypofractionation with the new Leksell Gamma Knife ICON can be a valuable alternative.