Microsurgical removal of intramedullary spinal cord gliomas in a rat spinal cord decreases onset to paresis, an animal model for intramedullary tumor treatment

Objective: Intramedullary spinal cord tumors (IMSCT) pose significant challenges given their recurrence rate and limited treatment options. Using our previously described rat model of IMSCT, we describe a technique for microsurgical tumor resection and present the functional and histopathological analysis of tumor progression. Methods: Twenty-four Fischer 344 rats were randomized into two groups. All animals received a 5-μl intramedullary injection of 9L gliosarcoma cells. Animals were evaluated daily for signs of paralysis using the Basso, Beattie, and Bresnahan (BBB) scale. Group 1 continued with daily assessments using the BBB scale following tumor implantation, but received no further treatment. Group 2 underwent surgical removal of intramedullary tumor on postoperative day five. At a BBB score less than 5 (e.g., functional paraplegia), all animals of both groups were killed and sent for histopathological analysis. Results: Group 1 had a median onset of functional hind limb paraplegia at 15±1.0 days. Group 2 had a median onset of hind limb paresis at 53±0.46 days. Hematoxylin-eosin cross-sections confirmed the presence of intramedullary 9L tumor invading the spinal cord in both groups. Conclusion: Animals with 9L IMSCTs consistently developed hind limb paraplegia in a reliable and reproducible manner. Animals undergoing microsurgical resection of IMSCT had a significant delay in the onset of functional paraplegia compared to the untreated controls. These findings suggest that this model may mimic the behavior of IMSCTs following operative resection in humans and thus may be used to examine efficacy of new treatment options for high-grade intramedullary tumors.