Follow-up MR findings of spinal foraminal nerve sheath tumors after stereotactic irradiation

The purpose of this study was to investigate follow-up MR findings of spinal foraminal nerve sheath tumors after stereotactic irradiation. 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. 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. 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. (author)