SHM Converge Scientific Abstract ePoster Gallery-False Alarm: Arachnoiditis Masquerading as CNS Malignancy

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A 50-year-old previously healthy man developed 3 weeks of progressive low back pain, bilateral leg weakness, perineal numbness, and night sweats after a recent tooth extraction. Exam showed lumbar tenderness, bilateral proximal leg weakness, and positive straight-leg raise. Inflammatory markers were elevated, and because spinal epidural abscess (SEA) was suspected, he was started on vancomycin and ceftriaxone.<br /><br />Multiple lumbar puncture attempts failed, so a C1-C2 puncture was performed. CSF showed pleocytosis, elevated protein, low glucose, and negative Gram stain/culture, but cytology unexpectedly showed plasma cells, raising concern for leptomeningeal myeloma. However, extensive workup including serum/urine electrophoresis, immunofixation, free light chains, flow cytometry, PET-CT, and bone marrow biopsy found no evidence of a clonal plasma cell disorder.<br /><br />MRI of the lumbar spine revealed diffuse inflammatory enhancement, microabscesses, and thecal sac involvement consistent with arachnoiditis secondary to SEA. The patient completed 6 weeks of daptomycin and improved neurologically by 4-week follow-up.<br /><br />The case highlights that SEA is often difficult to diagnose because the classic triad of fever, back pain, and neurologic deficits is present in fewer than 10% of patients at presentation. Arachnoiditis, especially the adhesive form, can mimic infection, autoimmune disease, or malignancy. In this patient, repeated failed lumbar punctures suggested dense arachnoid adhesions, and the plasma cells in CSF likely reflected a reactive inflammatory process rather than cancer. Improvement with antibiotics and absence of monoclonal or clonal findings supported this conclusion.<br /><br />Takeaway: SEA-associated arachnoiditis can imitate neoplastic disease when plasma cells are present in CSF.

Asset Subtitle

Harleen K. Sidhu

Meta Tag

Author List Adithan Ganesh, Hannah Hugo, Harleen K. Sidhu, Mohamed Abdelghffar, Oikigbeme Oikeh

Category Clinical Vignettes

Concept Spinal Epidural Abscess

Concept Neurologic Deficit

Concept Arachnoiditis

Concept Cerebrospinal Fluid

Concept Leptomeningeal Myeloma

Distinguished Non-Finalist

Presenter Organization Department of Medicine, NYC Health + Hospitals/Elmhurst, Icahn School of Medicine at Mount Sinai

Presenting Author Harleen K. Sidhu

Track Adult

Keywords

spinal epidural abscess

arachnoiditis

plasma cells in CSF

leptomeningeal myeloma

lumbar back pain

neurologic deficits

vancomycin

ceftriaxone

daptomycin

reactive inflammatory process

Spinal Epidural Abscess

Neurologic Deficit

Arachnoiditis

Cerebrospinal Fluid

Leptomeningeal Myeloma