Intradural extramedullary spinal metastases of non-neurogenic origin: a distinct clinical entity or a subtype of leptomeningeal metastasis? A case-control study.

BACKGROUND: Leptomeningeal metastases from carcinoma are still poorly understood.

OBJECTIVE: To better define the management of unique intradural extramedullary spinal metastases (IESM) from solid cancers of non-neurogenic origin, in particular regarding leptomeningeal metastasis (LM).

METHODS: We conducted a retrospective, multicenter, case-control study including 11 patients with IESM matched with 11 patients with LM. Primary endpoint was overall survival; secondary endpoints were diagnostic criteria and prognostic factors.

RESULTS: Descriptive analysis showed a clinically significant difference between IESM and LM patients regarding preexisting neurological deficit (45.5% vs 90.1%, P = .06) and malignant cells in cerebrospinal fluid (0% vs 54.5%, P = .03). The median overall survival was significantly higher for IESM patients (732 days) than for patients with LM (53 days; P < .0002). Multivariate analysis showed that preexisting neurological deficit was a negative prognostic factor for overall survival (hazard ratio: 10.2; 95% confidence interval: 1.88-102; P = .04), in contrast to functional improvement with treatment (hazard ratio: 0.01; 95% confidence interval: 0.00-0.52; P = .04). We propose the following diagnostic criteria for IESM: (1) a solid lesion located within the intradural extramedullary space, (2) the absence of other leptomeningeal lesion seen on full-spine injected magnetic resonance imaging, (3) the absence of malignant cells in cerebrospinal fluid, and (4) a histological confirmation of the metastatic nature of the lesion.

CONCLUSION: The significant difference in survival between IESM and LM suggests that they are 2 distinct evolutions of the metastatic disease. Distinguishing IESM also has therapeutic consequences because patients can benefit from a focal surgical treatment with functional improvement and extended survival.