Greene, Karl A.

BACKGROUND Ecchordosis physaliphora (EP), a benign extraosseous notochordal remnant, has been found in 0.4%–2% of autopsies. It most commonly occurs on the dorsal surface of the clivus and is rarely symptomatic. Extraosseous notochordal lesions involving the spine are also rare, with the majority being diagnosed as chordoma. OBSERVATIONS The authors report a case of an extradural extraosseous notochordal lesion within the left L5–S1 nerve root foramen resulting in left lumbar L5 radiculopathy in a 46-year-old woman. Microdecompression at the left lumbar L5–S1 level permitted successful removal of the lesion and complete resolution of radiculopathy. The combined histopathological and retrospective imaging findings were felt to be consistent with EP. Thirty-nine-month follow-up imaging revealed no recurrence of the lesion, and the patient remains asymptomatic at last follow-up. LESSONS Challenges in diagnosing EP, particularly distinguishing it from extraosseous chordoma, and the implications of diagnostic terminology on the management of these lesions are discussed. https://thejns.org/doi/10.3171/CASE26203