The authors report on a patient in whom monoradicular pain was caused by ganglionitis of a spinal nerve. Neuroimaging and intraoperative findings identified what were thought to be tumorlike changes in the affected nerve root. The neuropathological examination, however, revealed typical signs of ganglionitis. This rare inflammation usually appears with viral infections, as part of paraneoplastic symptoms, or in the presence of Sjögren disease. Because all of these differential diagnoses were negative in the treated patient, chronic nerve root compression due to disc herniation was suspected as the causative factor for the spinal ganglionitis.