Central Nervous System Diffuse Large B-Cell Lymphoma Diagnosed With Cauda Equina Biopsy: A Visual Vignette

We report a case of a 44-yr-old immunocompetent man from the Ivory Coast with no significant medical history. He was admitted to the intensive care unit after presenting with neurogenic pain, diffuse weakness, decreased lower limb sensation, and urinary retention. Initial examination revealed nuchal rigidity, diffuse hypoesthesia, and against gravity asymmetric paresis, which preferentially affected the left distal upper and proximal lower limbs. He then rapidly deteriorated, with worsening weakness and an altered level of consciousness. Whole spine magnetic resonance imaging revealed multilevel leptomeningeal and spinal cord enhancement (Fig. 1), as well as severe widespread involvement of the cauda equina, nearly obliterating the subarachnoid space (Fig. 2). Brain magnetic resonance imaging showed similar abnormalities and the patient required an external ventricular drain for hydrocephalus. Imaging and clinical presentation suggested subacute lymphocytic meningitis secondary to tuberculosis or fungal infection. Neurosarcoidosis was also considered in the differential diagnosis. An empirical treatment of Decadron and an antituberculosis drug regimen was started, but the patient continued to deteriorate.FIGURE 1: Cervical spine magnetic resonance imaging revealed leptomeningeal enhancement extending along the spinal cord with lesions that appear to extend into the spinal cord or minimally into the anteromedian and posteromedian fissure on axial sequences.FIGURE 2: Thoraco-lumbar spine magnetic resonance imaging revealed leptomeningeal enhancement extending to the thoracic spinal cord and diffuse enhancement of all cauda equina roots affecting virtually all the subarachnoid space.Initial lumbar puncture revealed markedly increased cerebrospinal fluid protein (29.30 g/L) and cell count (740*106) (flow cytometry: 92% lymphocytes; 27% polyclonal B, 67% T cells), and very low glucose (0.3 mmol/L). There was no evidence of lymphoproliferative syndrome on repeat lumbar puncture. Cerebrospinal fluid tuberculosis PCR and mycobacterium cultures were negative. Autoimmune antibodies and extensive infectious workup serology were also negative. A nerve biopsy at the level of the cauda equina was then performed, considering the lack of improvement with empiric treatment. This led to a diagnosis of primary diffuse large B-cell lymphoma of the central nervous system, and chemotherapy was initiated. The patient has been improving with medical treatment and rehabilitation. Aside from central nervous system lymphoma,1 two main conditions can exhibit the striking imaging findings displayed in this report, namely, tuberculosis2 and neurosarcoidosis.3 Diagnosis is challenging because of variability in disease presentation and limitations in investigations. Demonstration of Mycobacterium tuberculosis in the cerebrospinal fluid is considered the ‘gold standard’ for diagnosing tuberculous meningitis.2 Neurosarcoidosis can also manifest in various ways, including medullary and cauda equina involvement, and tends to affect a younger population.3 Other cases of large B-cell lymphoma with cauda equina involvement at presentation and absence of neoplastic cells in cerebrospinal fluid flow cytometry have been reported.1 Therefore, nerve biopsy should be considered in the absence of a diagnosis.