Purpose: The purpose of this study was to investigate follow-up MR findings of spinal foraminal nerve sheath tumors after stereotactic irradiation.
Materials and methods: Thirty-five foraminal nerve sheath tumors in 28 patients who underwent stereotactic radiosurgery (SRS) (n = 28) or stereotactic radiotherapy (SRT) (n = 7) were included. The MR images were reviewed to identify serial changes in tumor volume and intratumoral necrosis. Growth and shrinkage were defined as volume changes of ±19.7 % or more; stability was within ±19.7 %. Transient swelling was defined as shrinkage preceded by significant growth. A tumor with shrinkage or stability was regarded as tumor control.
Results: Of 35 tumors, 16 (46 %) were stable, 14 (40 %) shrunk, and 5 (14 %) grew. Transient swelling was seen for 13 (37 %) lesions. Newly developed intratumoral necrosis was observed for 19 (54 %) of 35 tumors and was significantly associated with transient swelling (p = 0.039) and with tumor control (p = 0.017). SRS was not significantly associated with transient swelling.
Conclusion: In follow-up MR images of spinal foraminal nerve sheath tumors after stereotactic irradiation, newly developed intratumoral necrosis and transient swelling were often seen. Intratumoral necrosis was associated with transient swelling and tumor control.