311 - Cranial Neuropathy Outcomes Following Stereotactic Radiosurgery or Radiotherapy for Skull Base Meningioma

Y. Kesbeh¹, A. Beighley², N. J. Zhou², J. Rahimian¹, K. Lodin¹, M. R. Girvigian¹, and O. Bhattasali¹; ¹Southern California Permanente Medical Group, Los Angeles, CA, ²Kaiser Permanente Los Angeles Medical Center, Los Angeles, CA

Purpose/Objective(s): Cranial neuropathy is a common presenting symptom or possible complication following treatment of skull base meningioma. This study evaluates the impact of radiotherapy (RT) on pre-existing cranial neuropathy and evaluates the risk of new or worsening cranial neuropathy post-treatment.

Materials/

Methods: Retrospective chart review was conducted of 343 patients with 358 skull base meningiomas treated with frameless LINAC-based image-guided stereotactic radiosurgery over one (n=101) or five (n=54) fractions or conventionally fractionated stereotactic radiotherapy (n=203) between January 2008 and January 2022. Patients with prior surgical management (n=75) were included. Cranial neuropathy status was obtained from history and physical exam as well as objective metrics including visual acuity/field testing or audiogram.

Results: Median follow-up was 99.6 months. Median patient age was 64 years. In the study cohort, 196 (54.7%) patients presented with 249 cranial neuropathies with 35 (9.8%) patients presenting with multiple cranial neuropathies. Median tumor volume was larger in patients with pre-RT cranial neuropathy compared to those without (5.61cc v. 2.89cc), p=<0.001. When evaluating all-comers, improvement or resolution was noted for 83 (33.3%) CN, whereas 41 (16.5%) worsened post-RT.

The most common cranial neuropathies at presentation included cranial nerve (CN) II (31.3%), CN V (23.7%), CN VI (16.9%), and CN VIII (14.1%). Of these, CN V was most likely to improve or resolve post-RT (p<0.001), whereas CN VIII was most likely to worsen post-treatment (p<0.001). Incidence of improved or resolved cranial neuropathy was as follows: CN II: 17.9%, CN V: 54.2%, CN VI: 52.4%, CN VIII: 8.6%. Incidence of worsened cranial neuropathy was as follows: CN II: 23.1%, CN V: 13.6%, CN VI: 2.4%, CN VIII: 40%. Among the 17 new cranial neuropathies that developed post-RT, 4 (23.5%) occurred in CN II, and 7 (41.2%) were attributable to local tumor progression.

Conclusion: This retrospective analysis reveals the differential impact of radiotherapy on cranial neuropathies in the management of skull base meningioma. Nearly one-third of cranial neuropathies improved or resolved post-RT with the most favorable responses observed in CN V and CN VI. In contrast, CN VIII was most likely to be negatively impacted by treatment with 40% of patients experiencing worsening of symptoms post-RT. Further research is warranted to identify CN-specific prognostic factors to optimize treatment strategies and improve quality of life for patients suffering from skull base meningiomas and associated cranial neuropathies.

Abstract 311 – Table 1: Rates of pre-radiation neuropathies and their outcomes post treatment *In order to meet the 10x10 table size submission requirement, CN I, IX, X, XI were removed due to their small sample size.

Cranial Nerve	Pre-RT	Stable	Improved	Resolved	Worse	New
II	78	45	14	2	17	5
III	17	11	1	5	0	2
IV	3	3	0	0	0	0
V	59	19	18	14	8	3
VI	42	19	14	8	1	3
VII	7	6	0	1	0	3
VIII	35	18	3	0	14	2
XII	3	1	2	0	0	0
Total	249	118	51	30	40	18