Intradural Cauda Equina Metastasis of Colorectal Adenocarcinoma: A Case Report.

Intradural spinal metastasis of non-neurogenic tumors is rare. Even more uncommon is intradural metastasis involving the cauda equina. Among these, colorectal adenocarcinoma metastasizing to the cauda equina is exceedingly rare, with no previously documented cases. We report a case of a 44-year-old male with a history of descending colon adenocarcinoma, initially treated with laparoscopic resection in 2011, followed by radical proctectomy for recurrent sigmoid adenocarcinoma in 2013. Over time, he developed progressive left-sided sciatica and foot drop. Imaging revealed an intradural extramedullary lesion at the cauda equina. The patient underwent L4-S2 left hemilaminectomy and S2 foraminectomy, with histopathology confirming metastatic adenocarcinoma. His postoperative recovery was uneventful, with significant pain relief and partial motor function improvement. However, local recurrence occurred at 16 months postoperatively, and the patient passed away 5.8 years after surgery. This case represents the first reported instance of intradural cauda equina metastasis from colorectal adenocarcinoma. The presumed metastatic route was via the Batson venous plexus, as systemic metastases were absent. Despite surgical resection improving symptoms, the long-term prognosis remains poor. Contrast-enhanced T1-weighted MRI is crucial for diagnosis, and total resection may contribute to prolonged survival in select patients.