Repeat gamma knife radiosurgery for recurrent trigeminal neuralgia: a systematic review and meta-analysis

Trigeminal neuralgia is a disorder of the trigeminal nerve that results in intense episodic pain. Medical management is commonly used as the first therapeutic intervention; however, some patients become resistant to it, requiring further interventions. Stereotactic radiosurgery with the Gamma Knife (GK) is safe and effective in multiple retrospective series. However, in some cases, repeat radiosurgery may be needed, aiming to improve the patient's pain in the long term.

We performed a systematic review and meta-analysis following the PRISMA guidelines. We included papers in English that reported patients with trigeminal neuralgia who didn't have their pain solved with standalone medications or a single dose of GK, needing repeat GK. All statistical analyses were conducted using R.

Twenty-one studies met the inclusion criteria, totaling 2,486 patients initially treated and 2,020 undergoing repeat GKRS. The majority were female, with median ages 54.5-79.6 years, and idiopathic TN represented ~ 85% of cases. Most procedures targeted the trigeminal root entry zone using 70-80 Gy marginal doses. Pain relief occurred in 70-90% of patients, with marked improvement in BNI scores (typically IV-V to I-IIIb). Median follow-up ranged 14-74 months, and recurrence occurred in 10-35% of cases. Facial sensory disturbances were reported in 20-45%, while bothersome dysesthesias and anesthesia dolorosa were rare (< 3%). Meta-regression, including up to 10 studies, found no significant correlation between pain relief and age (p = 0.5682), pain duration (p = 0.3593), interval since last GKRS (p = 0.4093), or dose (p = 0.7857). Heterogeneity remained high (I² = 55.6-91.8%, p < 0.0001), indicating inter-study variability.

Repeat GKRS is a safe and effective option for TN patients experiencing persistent or recurrent pain after initial radiosurgery. Despite inter-study variability, outcomes support its use for long-term pain control. Further prospective studies are needed to optimize patient selection and treatment parameters.