Gamma Knife Stereotactic Radiosurgery for Trigeminal Neuralgia Secondary to Recurrent Skull Base Malignancies

Purpose/Objective(s): To assess the outcome of Gamma Knife stereotactic radiosurgery (GKS) reirradiation for patients with painful trigeminal neuralgia secondary to malignant skull base tumor recurrence.

Materials/Methods: Between 2009 and February 2015, 20 patients previously irradiated to the head and neck were treated with GKS for palliation of trigeminal neuralgia secondary to malignant skull base tumors. Those without local progression or recurrence and >1 month follow-up, were retrospectively assessed for symptom palliation. Self-reported pain was evaluated using the Numeric Rating Scale (NRS) and M.D. Anderson Symptom Inventory-Head & Neck “Pain Item” (MDASI-HN Pain) scores (0–10). Frequency of PRN analgesic use and overall opioid requirement were assessed. Opioid dose was reported as a fentanyl patch-equivalent dose (FED) if scheduled and an oral morphine-equivalent dose (OMED) if PRN for breakthrough pain. The Chi-Squared and Student’s t-tests were used to determine differences before and after GKS.

Results: Four patients (25%) were excluded due to local disease. One had local progression on first follow-up, 3 had local recurrence from disease progression outside GKS volume. There were 2 deaths; both were among those who recurred locally. Sixteen patients were assessed for symptom palliation with a median follow-up of 6.2 months (3.0 -19.9 months). Fifteen patients were treated with a single fraction GK-SRS to a median dose of 16 Gy (range 10–20 Gy) prescribed to 50% (range 43–55%) and one patient treated with the GK-Extend system to 24 Gy in 3 fractions prescribed to 50%. At 3 months post GKS: The NRS scores (n = 16) decreased from 4.92 ± 3.79 to 1.39 ± 2.17 (p < 0.01); MDASI-HN Pain scores (n = 10) decreased from 4.97 ± 1.89 to 1.89 ± 1.61 (p < 0.01); scheduled FED (n = 16) decreased from 58.2 ± 109.1 to 21.8 ± 36.3 mcg/hr (p < 0.01); PRN OMED (n = 16) decreased from 48.4 ± 87.6 to 11.2 ± 22.3 mg/day (p < 0.01); and frequency of PRN any analgesic use (n = 15) decreased from 0.44 ± 0.62 to 1.13 ± 0.92 per day (p < 0.05). At 6 months post GKS, 6 of 10 patients (60%) reported being pain free (NRS 0), with 4 (67%) completely off analgesic use. One patient treated early in our experience developed a temporary increase in trigeminal pain 3–4 days post GK-SRS requiring hospitalization. All subsequently treated patients were given a single dose of IV steroid immediately post GKS followed by a 2–3 week oral steroid taper, with no further cases of increased or new pain after treatment.

Conclusion: Early results after GKS for trigeminal pain secondary to malignant skull base tumor recurrence demonstrate a significant decrease in patient-reported pain and opioid requirement. More patients and longer follow-up are needed to assess durability of symptom relief and local control.