Primary leptomeningeal lymphoma of the cauda equina: a rare cause of radiculopathy

Abstract

Primary leptomeningeal lymphoma (PLML) is a particularly rare neoplasm, accounting for only 7% of all primary central nervous system lymphomas. PLML is defined as a syndrome of lymphomatous meningeal infiltration without identification of systemic lymphoma or parenchymal CNS lymphoma in the clinical course of the disease [6, 12]. The diagnosis is challenging and requires a high index of suspicion. Early diagnosis, however, is crucial as immediate treatment may be beneficial. We here report a case of PLML of the cauda equina to raise awareness for this disorder and reduce the delay to diagnosis in similar cases. A 69-year-old immunocompetent man complained about increasing low back pain and moderate weakness of the left leg, which had slowly developed over 1 year. Neurologic examination and electrodiagnostic studies indicated a left-sided L5–S1 radiculopathy. There was no evidence of polyneuropathy. MRI of the spine, the pelvis, and the brain, including contrast-enhanced sequences, was unremarkable. Routine lumbar puncture yielded normal findings. The patient underwent an extensive laboratory and image work-up to rule out malignant, autoimmune, or infectious disease. Due to negative findings, he was discharged to home. High-resolution, contrast-enhanced MR neurography [7, 10] and a second lumbar tap were performed 36 days later. Analysis of the cerebrospinal fluid (CSF) revealed 0 cells/ll with a normal glucose and protein content and imaging findings were again inconclusive (Fig. 1a and b). Short inversion time inversion recovery (STIR) images, however, then illustrated hyperintensity and contrast enhancement of the left piriformis muscle and the left medial gluteal muscle, suggesting acute denervation (Fig. 1c). Subsequent treatment with intravenous methylprednisolone 10 mg/kg/day for 5 days was without clinical benefit at that point. Only 9 months later, the patient was readmitted with a pronounced flaccid lower extremity paraparesis and severe low back pain. Contrast-enhanced MRI of the lumbar spine then disclosed abnormal thickening and marked linear enhancement coating multiple cauda equina nerve roots highly suggestive of leptomeningeal infiltration by tumor (Fig. 2a–c). Urgent analyses of the CSF revealed elevated protein (439 mg/dl; normal range: 15–45) and a lymphocytic pleocytosis (70 cells/ll) with many atypical cells consistent with lymphoma. A biopsy of an anterior cauda equina nerve root as highlighted by immunohistochemistry with S100 (Fig. 2d) and NSE revealed a massive diffuse interstitial infiltrate of atypical lymphocytic cells, that reached the marginal area of the small specimen with epithelial membrane antigen (EMA) positive cells indicating leptomeningeal infiltration [14]. The cells expressed CD20 and CD79, but were negative for Kl-1, EMA, CD56, M. Beitzke (&) C. Enzinger F. Fazekas Department of Neurology, Medical University of Graz, Auenbruggerplatz 22, 8036 Graz, Austria e-mail: markus.beitzke@klinikum-graz.at