Gamma Knife surgery (GKS) is an effective treatment option for intractable trigeminal neuralgia (TN). The incidence of trigeminal nerve dysfunction, such as facial numbness or dysesthesia, has been reported to be higher than previously published, and the degree and prognosis of trigeminal nerve dysfunction has not been well evaluated. The authors evaluated the incidence, timing, degree, and outcome of trigeminal nerve dysfunction after GKS for TN.
One hundred four patients with medically refractory TN were treated by GKS. Thirty-nine patients were men and 65 were women; their median age at GKS was 74 years. Using a single isocenter and a 4-mm collimator, 80 or 90 Gy was directed to the trigeminal nerve root. Follow-up data were obtained at clinical examinations every 3–6 months after GKS. Each patient's pain-control status and degree of trigeminal nerve dysfunction were recorded. The incidence, timing, and degree of dysfunction (assessed using the Barrow Neurological Institute facial numbness scale [BNI-N]) and the prognosis and factors related to trigeminal nerve dysfunction were analyzed.
The median duration of follow-up in these patients was 37 months (range 6–121 months). At the final clinical visit, a pain-free status was still observed in 71 patients (68.3%). In 51 patients (49.0%), new or increased trigeminal nerve dysfunction developed at a median of 10.5 months (range 4–68 months) after GKS. In 24 patients (23.1%), this dysfunction was categorized as BNI-N Score II, in 20 patients (19.2%) as BNI-N Score III, and in 7 patients (6.7%) as BNI-N Score IV. Among those patients, 18 patients, including 3 patients with BNI-N Score IV, experienced improvement in nerve dysfunction between 24 and 108 months after GKS (median 52.5 months). At the final clinical visit, 43 patients (41.3%) reported having some trigeminal nerve dysfunction: in 26 patients (25.0%) this was categorized as BNI-N Score II, in 13 patients (12.5%) as BNI-N Score III, and in 4 patients (3.8%) as BNI-N Score IV. The only independent factor that was correlated to all trigeminal nerve dysfunction and also specifically to bothersome trigeminal nerve dysfunction was pain-free status at the final clinic visit.
The incidence of trigeminal nerve dysfunction after GKS for TN was 49%. The severity of the dysfunction improved in one-third of the afflicted patients, even in those with severe dysesthesia at long-term follow-up. A strong relationship between TN and good pain control was identified.
Abbreviations used in this paper: BNI = Barrow Neurological Institute; BNI-N = BNI facial numbness scale; BNI-P = BNI pain intensity scale; CISS = constructive interference in the steady state; DREZ = dorsal root entry zone; GKS = Gamma Knife surgery; TN = trigeminal neuralgia.
BalamuckiCJStieberVWEllisTLTatterSBDeguzmanAFMcMullenKP: Does dose rate affect efficacy? The outcomes of 256 Gamma Knife surgery procedures for trigeminal neuralgia and other types of facial pain as they relate to the half-life of cobalt. J Neurosurg105:730–7352006
LittleASShetterAGShetterMEBayCRogersCL: Long-term pain response and quality of life in patients with typical trigeminal neuralgia treated with gamma knife stereotactic radiosurgery. Neurosurgery63:915–9242008
MassagerNNissimOMurataNDevriendtDDesmedtFVanderlindenB: Effect of beam channel plugging on the outcome of gamma knife radiosurgery for trigeminal neuralgia. Int J Radiat Oncol Biol Phys65:1200–12052006
RiesenburgerRIHwangSWSchirmerCMZerrisVWuJKMahnK: Outcomes following single-treatment Gamma Knife surgery for trigeminal neuralgia with a minimum 3-year follow-up. Clinical article. J Neurosurg112:766–7712010
RogersCLShetterAGFiedlerJASmithKAHanPPSpeiserBL: Gamma knife radiosurgery for trigeminal neuralgia: the initial experience of The Barrow Neurological Institute. Int J Radiat Oncol Biol Phys47:1013–10192000