Spinal subependymoma mimicking an intradural extramedullary tumor: illustrative case.

BACKGROUND

Spinal subependymomas are rare, benign tumors that typically arise within the spinal cord and usually appear as intramedullary lesions on MRI. The authors report a rare case of cervical spinal subependymoma with exophytic growth that mimicked an intradural extramedullary tumor on MRI.

OBSERVATIONS: A 53-year-old man presented with right-sided paresthesia. MRI revealed a spinal tumor causing marked spinal cord compression. The lesion was isointense on T1-weighted images, slightly hyperintense on T2-weighted images, and showed no gadolinium enhancement. A focal CSF cleft between the tumor and spinal cord led to a preoperative diagnosis of an intradural extramedullary tumor, and schwannoma was suspected. However, intraoperative pathological examination suggested a low-grade glioma, prompting a change in the surgical strategy. Subtotal resection was therefore performed to preserve neurological function. Histological examination subsequently confirmed the diagnosis of subependymoma.

LESSONS: Spinal subependymoma may rarely present with an apparent intradural extramedullary appearance on MRI. The presence of a CSF cleft and exophytic growth should not exclude an intramedullary origin. Awareness of this atypical presentation and avoidance of anchoring bias are essential for appropriate intraoperative decision-making. When subependymoma is suspected, maximal safe resection should be prioritized over aggressive tumor removal to preserve neurological function. https://thejns.org/doi/10.3171/CASE26728.