Effect of pseudoprogression of vestibular schwannomas on dynamics of trigeminal and facial nerves dysfunction after stereotactic radiosurgery

Abstract

The use of stereotactic radiosurgery (SRS) in the treatment of vestibular schwannomas (VS) is due to a high level of local control of tumor growth, a lower level of functional impairment, a relatively low cost of treatment compared to microsurgery, and the preservation of a high quality of life [1–7]. The development of post-radiation pseudoprogression of the VS can lead to increased compression of adjacent brain structures, including the trigeminal and facial nerves with the appearance of their irritation or lack of function. The purpose of the study: to investigate the effect of post-radiation pseudoprogression on the function of cranial nerves 5 and 7 after SRS. Material and methods. The analysis included 128 patients with 3 or more control MRIs and a follow-up period of 12 months and over, who had at least 3 control examinations by a neurologist and otoneurologist. The median clinical follow-up was 52 months. The analyzed patients (n=128) were divided into 2 main groups: group 1 (n=99) — without previous microsurgery (MS), group 2 (n=29) — previously operated patients. Results. Irritation of nerves 5 and 7 is observed after SRS for VS exclusively against the background of pseudoprogression. Persistent de novo facial nerve failure after SRS is a rare complication (0.9 %). Symptoms of dysfunction of the 5th and 7th nerves predominate in the group of large VS (stages C and D according to Hasegawa) (p<0.0001). The prolonged course of pseudoprogression determines a tendency to longer dysfunction of the cranial nerves, but does not affect the final result. Conclusion. Irritation of the 5th and 7th nerves, relieved by anticonvulsants, is not an indication for surgical removal of the tumor or re-irradiation, as it goes away on its own due to subsequent natural shrinkage of the tumor. However, the pharmacoresistant course of trigeminal neuralgia may be due to compression of the trigeminal nerve root between the tumor and petrous apex, and therefore subtotal tumor removal may be justified for root decompression.