Notochord-derived lesion presenting with cerebrospinal fluid rhinorrhea: illustrative case.

backgroundChordomas are rare neoplasms derived from the notochord, primarily affecting the skull base and sacral regions. While cranial nerve deficits are common, CSF rhinorrhea as an initial symptom is rare. Ecchordosis physaliphora (EP), another notochord-derived lesion, is typically asymptomatic but may also be present with CSF leakage. Differentiating between these entities remains challenging due to overlapping histopathological and imaging features. OBSERVATIONS: The authors report the case of a woman in her 50s with persistent CSF rhinorrhea for 4 months. Imaging revealed a central clival defect with mucosal protrusion, and endoscopic endonasal repair identified a fragile, whitish lesion. Histopathological examination confirmed a chordoma with features suggestive of EP, including low Ki-67 labeling. Given the lack of contrast enhancement on MRI and the benign clinical course, EP was suspected rather than an aggressive chordoma. LESSONS: This case highlights the need to consider notochordal lesions in patients with idiopathic CSF rhinorrhea, particularly with clival defects. When CSF leakage with a suspected fistula at the central clivus is encountered, a notochord-derived lesion should be considered, and skull base reconstruction should be performed accordingly. https://thejns.org/doi/10.3171/CASE25157.