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

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.

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.

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.

Our data demonstrate high spatial targeting accuracy of frameless IGRS for TGN with only nominal intra-fraction 6-dimensional corrections.