CLINICAL ARTICLE J Neurosurg 127:219–225, 2017 S tereotactic radiosurgery (SRS) is the least invasive procedure for managing medically refractory typi- cal trigeminal neuralgia (TN). 10,14,18 In some cases, a 3- to 5-mm zone of contrast enhancement develops after SRS ablation at the radiosurgical trigeminal target seen on high-defnition MRI scans. 9,22 In a baboon model, this contrast enhancement was observed at 6 months after SRS and correlated with pathological evidence of both small and large myelinated fber degeneration and region- al infammation in the retrogasserian nerve. 8 Although the ABBREVIATIONS BNI = Barrow Neurological Institute; BNI-NS = BNI Numbness Scale; BNI-PS = BNI Pain Scale; SRS = stereotactic radiosurgery; TN = trigeminal neural- gia. SUBMITTED January 14, 2016. ACCEPTED May 13, 2016. INCLUDE WHEN CITING Published online July 29, 2016; DOI: 10.3171/2016.5.JNS16111. The clinical signifcance of persistent trigeminal nerve contrast enhancement in patients who undergo repeat radiosurgery Seyed H. Mousavi, MD, 1 Berkcan Akpinar, BA, 2 Ajay Niranjan, MD, 1 Vikas Agarwal, MD, 3 Jonathan Cohen, BA, 2 John C. Flickinger, MD, 4 Douglas Kondziolka, MD, 5 and L. Dade Lunsford, MD 1,4 Departments of 1 Neurological Surgery, 3 Radiology, and 4 Radiation Oncology, University of Pittsburgh Medical Center; 2 University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; and 5 Department of Neurological Surgery, New York University Medical Center, New York, New York OBJECTIVE Contrast enhancement of the retrogasserian trigeminal nerve on MRI scans frequently develops after radiosurgical ablation for the management of medically refractory trigeminal neuralgia (TN). The authors sought to evalu- ate the clinical signifcance of this imaging fnding in patients who underwent a second radiosurgical procedure for recur- rent TN. METHODS During a 22-year period, 360 patients underwent Gamma Knife stereotactic radiosurgery (SRS) as their frst surgical procedure for TN at the authors’ center. The authors retrospectively analyzed the data from 59 patients (mean age 72 years, range 33–89 years) who underwent repeat SRS for recurrent pain at a median of 30 months (range 6–146 months) after the frst SRS. The isocenter was 4 mm, and the median maximum doses for the frst and second proce- dures were 80 Gy and 70 Gy, respectively. A neuroradiologist and a neurosurgeon blinded to the treated side evaluated the presence of nerve contrast enhancement on MRI series at the time of the repeat procedure. The authors correlated the presence of this imaging change with clinical outcomes. Pain outcomes and development of trigeminal sensory dys- function were evaluated with the Barrow Neurological Institute (BNI) Pain Scale and BNI Numbness Scale, respectively. The mean length of follow-up after the second SRS was 58 months (95% CI 49–68 months). RESULTS At the time of the repeat SRS, contrast enhancement of the trigeminal nerve on MRI scans was observed in 31 patients (53%). Five years after the SRS, patients with this enhancement had lower actuarial rates of complete pain relief after the repeat SRS (27% [95% CI 7%–47%]) than patients without the enhancement (76% [95% CI 58%–94%]) (p < 0.001). At the 5-year follow-up, patients with the contrast enhancement also had a higher risk for trigeminal sensory loss after repeat SRS (75% [95% CI 59%–91%]) than patients without contrast enhancement (26% [95% CI 10%–42%]) (p = 0.001). Dysesthetic pain after repeat SRS was observed for 8 patients with and for 2 patients without contrast en- hancement. CONCLUSIONS Trigeminal nerve contrast enhancement on MRI scans observed at the time of a repeat SRS for TN was associated with less satisfactory pain control and more frequently detected facial sensory loss. Residual contrast enhancement at the time of a repeat SRS may warrant consideration of dose reduction or further separation of the radio- surgical targets. https://thejns.org/doi/abs/10.3171/2016.5.JNS16111 KEY WORDS trigeminal neuralgia; stereotactic radiosurgery; MRI; contrast enhancement; pain ©AANS, 2017 J Neurosurg Volume 127 • July 2017 219 Unauthenticated | Downloaded 02/16/23 03:15 PM UTC