Intra-fractional corrections and clinical outcomes in frameless image-guided radiosurgery for trigeminal neuralgia.

Purpose: Precision targeting is crucial to successful stereotactic radiosurgery for trigeminal neuralgia (TGN). We investigated the impact of intra-fractional 6-dimensional corrections during frameless image-guided radiosurgery (IGRS) for pain outcome in TGN patients. Materials and methods: A total of 41 sets of intra-fractional corrections from 35 patients with TGN treated by frameless IGRS from 2009 to 2013 were retrospectively studied. For each IGRS, the intra-fractional 6-dimensional shifts were conducted at 6 couch angles. Clinical pain outcome was recorded according the Barrow Neurological Institute (BNI) 5-points score. The relationship in 6-dimensional corrections and absolute translational distances between patients with pain relief score points <2 versus ≥2 were analyzed. Results: The absolute mean lateral, longitudinal, and vertical translational shifts were 0.46 ± 0.15 mm, 0.36 ± 0.16 mm and 0.21 ± 0.08 mm, respectively, with 97% of translational shifts being within 0.7 mm. The absolute mean lateral (pitch), longitudinal (roll), and vertical (yaw) rotational corrections are 0.33 ± 0.24°, 0.18 ± 0.09°, and 0.27 ± 0.15°, respectively, with 97% of rotational corrections being within 0.6°. The median follow-up duration for pain outcome was 26 months after IGRS. The average calculated absolute shift for patients with pain relief <2 and ≥2 BNI points, were 0.228 ± 0.008 mm and 0.259 ± 0.007 mm, respectively. There was no statistically significant difference in the translational shifts, rotational corrections or absolute distances between these two patient groups. Conclusions: Our data demonstrate high spatial targeting accuracy of frameless IGRS for TGN with only nominal intra-fraction 6-dimensional corrections.