Radiation Necrosis Following Stereotactic Radiosurgery for Trigeminal Neuralgia

The patient experienced some improvement in the emergency room, and tissue plasminogen activator was not administered. [...]MRI alone has low specificity (33.4%) and is usually insufficient for distinguishing radiation necrosis from tumor recurrence.2 Several studies have compared more advanced imaging techniques.3 Shah et al. found that single-photon emission computed tomography has the highest specificity (97.8%); meanwhile, MRS has good sensitivity (85.9%) and specificity (79.9%).2 Zhang et al. studied MRS in particular and found that metabolite ratios Cho/NAA (sensitivity 88%; specificity 86%) and Cho/Cr (sensitivity 83%; specificity 83%) were both useful in distinguishing radiation necrosis from glioma recurrence.4 A literature review identified one previously reported case of radiation necrosis following stereotactic radiosurgery for trigeminal neuralgia.5 In Montoure et al.’s report, the patient had undergone TomoTherapy for trigeminal neuralgia 1 year prior to the development of a ring-enhancing lesion in the mesial temporal lobe (Table 1). Comparison of cases from literature review Authors and year Montoure et al.5 Present study Age at Dx (years)/gender 74/F 85/M Radiation type TomoTherapy (6× photon energy mode) CyberKnife Radiation dose 40 Gy 64 Gy Radiation location Unknown Right Gasserian ganglion Time to presentation 1 year 16 months Presenting symptoms Gait instability, headache, and confusion Dysarthria, hemiparesis, and numbness MRI findings Ring enhancement in mesial temporal lobe with surrounding FLAIR hyperintensity Ring enhancement in mesial temporal lobe with surrounding FLAIR hyperintensity Diagnostic method Histological examination Clinical course and radiographic evidence (MRI and MRS) In summary, radiation necrosis is a complication of stereotactic radiosurgery that can present similarly to other entities such as high-grade glioma and is important to recognize in any patient who has had radiation to the central nervous system.