Fifty-eighth annual meeting of the american association of physicists in medicine
SU-F-T-631: Linear Accelerator-Based Frameless Extracranial Radiosurgery for Treatment of Occipital Neuralgia for Non-Surgical Candidates
Occipital neuralgia is a condition wherein pain is transmitted by the occipital nerves. Non-invasive therapies generally alleviate symptoms; however, persistent or recurring pain may require invasive procedures. Repeated invasive procedures upon failure are considered higher risk and are often contraindicated due to compounding inherent risk. SRS has not been explored as a treatment option largely due to the extracranial nature of the target (as opposed to the similar, more established trigeminal neuralgia), but advances in linear-accelerator frameless-based SRS now present an opportunity to evaluate the novel potential of this modality for this application.
Patient presented with severe occipital pain following decompression and fusion of the cervical vertebrae with prior intervention attempted via radiofrequency ablation yielding temporary pain cessation. A 0.6 mm slice spacing CT was obtained for treatment planning, and a cervical spine oriented 1.0 mm slice spacing CT myelogram was obtained for the purpose of defining the targeted C2 occipital dorsal root ganglion (to receive 80 Gy to the isocenter) and spinal cord.
The spinal cord was most proximally 12.0 mm from the isocenter receiving a maximum dose of 3.36 Gy, and doses to 0.35 and 1.2 cc of 1.84 Gy and 0.79 Gy, respectively. The brain maximum dose was 2.29 Gy. The treatment was successfully performed with a NovalisTX (Varian) equipped with ExacTrac stereoscopic x-ray image guidance (BrainLAB). Treatment time was 59 minutes for 18,323 MUs. Imaging was performed prior to each arc delivery resulting in twenty-one imaging sessions (twelve requiring positional corrections with the remaining verified within tolerance). The average deviation magnitude requiring a positional or rotational correction was 0.96±0.25 mm, 0.8±0.41° while the average deviation magnitude deemed within tolerance was 0.41±0.12 mm, 0.57±0.28°.
Linear accelerator-based frameless radiosurgery provides an accurate, non-invasive alternative for treating occipital neuralgia where an invasive procedure is contraindicated.