Filum terminale schwannoma with new onset of severe low back pain and radiculopathy: illustrative case.

backgroundSchwannomas are CNS WHO grade 1 benign peripheral nerve sheath tumors. They can occur anywhere in the body where there are peripheral nerves, but they are most common in the vestibular system. To the authors' knowledge, there has been only one previous report of their presentation in the filum terminale. OBSERVATIONS: The author present the case of a 36-year-old man who presented to the emergency department with acute-on-chronic right low back pain and shooting pain to his right groin with radiation to his knee. He was found to have an L1-2 intradural extramedullary lesion on MRI abutting the conus. His preoperative neurological examination was otherwise unremarkable, and he was promptly taken for L1-2 laminectomy and resection of the lesion. Final pathological diagnosis was intradural extramedullary cellular schwannoma, CNS WHO grade 1, of the filum terminale. Postoperative MRI demonstrated gross-total resection. The patient had new urinary fullness and constipation, which resolved by the 2-month follow-up, and otherwise recovered well with resolution of his back and leg pain. LESSONS: This case illustrates a rare presentation of an intradural extramedullary cellular schwannoma at the filum terminale, emphasizing the importance of a broad differential diagnosis. Resection of these neoplasms offers a definitive and safe treatment. https://thejns.org/doi/10.3171/CASE25333.