Stereotactic radio-neurosurgery for jugular foramen schwannomas

Abstract

Background: Stereotactic radiosurgery (SRS) represents a minimally invasive and valuable alternative for jugular foramen schwannomas (JFS), both as upfront and/or adjuvant treatment (in hybrid approaches).

Methods: We conducted a retrospective review of our cases treated at the Lausanne University Hospital (CHUV) from June 2010 to October 2023. Eleven patients underwent SRS, among whom three had prior surgery, two in our center in the frame of a planned combined approach and one in another center. Two patients received "volume-staged" SRS. The mean age at SRS was 60 years (median 68; range 29-83). Cranial nerve (CN) symptoms were present in six patients, while five were asymptomatic. The mean tumor volume at SRS was 2.1 cc (median 1.2; range 0.068-7.3 cc), with a 12 Gy marginal dose prescribed in all cases.

Results: The mean follow-up period was 3.9 years (median 2, range 1-7). Cranial nerve function improved after SRS in six patients, while five remained stable. At the last follow-up, all tumors showed a decrease in volume, except for one patient, who underwent surgery at 18 months after SRS, for volumetric increase at 6 and 12 months, with further XII^-th CN palsy and medulla oblongata compression. Although tumor decreased at 18 months, such patient needed microsurgical resection for symptom persistence and was further controlled. The mean tumor volume at 1 year post-SRS was 1.6 cc (median 0.55; range 0.028-7.77 cc), at 2 years was 1.31 cc (median 0.76; range 0.19-5), and at 3 years was 1.32 cc (median 0.59; range 0.23-4.8). No adverse radiation events were observed.

Conclusions: Stereotactic radiosurgery is considered a safe and effective treatment for jugular foramen schwannomas, ensuring high rates of tumor control in all patients over the long term. The cranial nerve function improved after SRS in the 6 patients who had deficits and the other 5 patients who had no deficits remained asymptomatic. For larger tumors, combined/hybrid approaches can be a valuable alternative, to obtain tumor control and to preserve neurological function.

Keywords: Cranial nerves; Gamma Knife; Jugular foramen; Schwannoma; Stereotactic radiosurgery.

Fig. 1

Illustration of all cases treated in Lausanne; the dosimetry is colored in yellow for single session treatments and in yellow and blue for staged volume treatments. Are depicted therapeutic images, as well as follow-up MRIs, co-registered with the therapeutic ones. For illustration purposes, we selected for detailed explanations the following: Case 3: example of an upfront SRS approach with initial tumor volume, 3 years after SRS and 7 years after SRS (with major decrease and 20.8% from the initial volume); Case 5: example of a volume-staged radiosurgery, with the first stage (a) and second stage (b). Case 8: example of a combined approach with preoperative volume, at the time of SRS, 6 months after SRS with transient tumor swelling and further decrease at 3 years after SRS

Fig. 2

Volume evolution after radiosurgery for each individual patient. The cases are numbered from 1 to 11. The letters “a” and “b” correspond respectively to “stage 1” and “stage 2” for each patient