Comparison of repeat GK-SRS for refractory or recurrent trigeminal neuralgia: Does dose matter

Abstract

Gamma Knife stereotactic radiosurgery (GK-SRS) is an important and minimally invasive treatment modality for patients with trigeminal neuralgia (TN). It is unclear, however, how best to manage patients whose pain is refractory or recurrent after the initial GK-SRS treatment. Here we report and compare the treatment outcomes for patients treated with repeat radiosurgery for refractory or recurrent TN with a low dose (70–75 Gy) at the University of Maryland Medical System (UM) and high dose (90 Gy) at the University of Kentucky Medical Center (UK). From 1996 to 2004, a total of 69 patients received repeat GK-SRS for refractory or recurrent TN at UM and UK. Complete follow-up data were available in 63 patients (64 procedures). Patients at UM (n = 28) underwent the repeat GK-SRS within a median of 13 months (range, 2–56 months) after the initial treatment. Median prescribed Dmax doses for the first and second treatments were 75 Gy (range, 70–80 Gy) and 70 Gy (range, 45–75 Gy), respectively. In addition, patients at UK (n = 35; GK-SRS = 36) underwent a second GK-SRS within a median of 12.5 months (range, 6–60 months) after the initial treatment. One patient required repeat treatment of both nerves. Median prescribed Dmax doses were 90 Gy for both first (range, 80–90 Gy) and second procedures (range, 70–90 Gy). Efficacy was measured through follow-up visits and standardized questionnaires. Pain relief was defined as: excellent (pain-free requiring no medications), good (pain-free but continuing medications), fair (≥50% pain reduction), and poor (<50% pain reduction). The median follow-up for UM and UK patients were 14 months (range: 1–65 months) and 19 months (range: 1–63 months), respectively. Following initial GK-SRS at UM, 24 of 28 patients (85.7%) had excellent (42.9%) or good responses (42.9%) responses. After the second GK-SRS procedure, pain outcomes were excellent in 11 (39.3%), good in 12 (42.9%), and poor in 5 (17.9%) patients, for a total complete pain relief rate of 82.4%. All 3 patients with poor response after the initial GK-SRS did not respond to second GK-SRS. Although 12 patients (42.9%) reported numbness after the second GK-SRS treatment, only 7 (25%) of these were new or increased. Four patients (14.2%) described this as somewhat bothersome; however, all 4 patients had complete pain relief. Similarly, following initial GK-SRS at UK, 20 out of 36 procedures (55.6%) achieved excellent (33.3%) or good (22.2%) responses. After the second GK-SRS procedure, pain outcomes were excellent in 23 (63.9%), good in 7 (19.4%), fair in 3 (8.3%), and poor in 3 (8.3%) patients, for a total complete pain relief rate of 83.3%. Of the 8 patients who were never pain free after the first treatment, 4 (50%) reported obtaining excellent results after the second procedure. Twelve patients (33%) reported numbness or dysesthesia after the second procedure, but only 9 (25%) were increased or new onset; only one (2.8%) patient reported this to be bothersome. Although the chance of achieving complete pain relief was similar in UM (median cumulative dose 150 Gy) and UK (median cumulative dose 180 Gy) patients after repeat GK-SRS, UK patients had a significantly higher chance of discontinuing all medications (p < 0.05). The toxicity was similar in both groups. Despite different cumulative doses, repeat GK-SRS provided similar rates of pain control in both the UK (83.3%) and UM (82.4%) groups. It appears that cumulative doses of 180 Gy increases the probability of discontinuing all medications compared to a cumulative dose of 150 Gy in patients with recurrent or refractory TN. Our study suggests that doses as high as 90 Gy are effective for treating refractory or recurrent trigeminal neuralgia pain, and cumulative doses up to 180 Gy to the Dmax appear safe with minimal residual bothersome side effects. Long-term follow-up is required to see if these results are durable. To date this is the largest reported series of repeat GK-SRS for TN