351 - A Diagnostic Dilemma: Paraneoplastic Sensorimotor Neuropathy Masquerading as Radiculopathy

Case Diagnosis: Paraneoplastic Sensorimotor Neuropathy

Case Description: A 51-year-old male presented to the ED complaining of worsening numbness and weakness in his lower extremities, that was exacerbated since a car accident 9 months prior. Additionally, he noted a 25 lb. weight loss over the past several months. His initial MRI showed a disc bulge. His electrodiagnostic studies revealed evidence of polyradiculopathy characterized by proximal demyelination and sensory polyneuropathy.

His clinical exam was notable for significant lower extremity atrophy, weakness, and sensory impairment coupled with mild upper extremity weakness. Laboratory workup revealed positive antinuclear antibodies and serum protein electrophoresis detected IgM lambda proteins. Cerebrospinal fluid studies revealed significant lymphocytic pleocytosis and elevated protein levels. Flow cytometry demonstrated a population of CD5-positive B-lymphocytes. Those findings were consistent with small lymphocytic lymphoma. The patient’s constellation of symptoms was concerning for paraneoplastic sensorimotor neuropathy. Patient was admitted to inpatient rehab and was started on high-dose steroids and oncology treatment with Ibrutinib.

Discussions: Paraneoplastic neurologic syndromes (PNS) is a rare autoimmune disorder that occurs secondary to occult malignancies, affecting approximately 0.1% of cancer patients. Diagnosing PNS can be challenging, owing to sparse clinical data and absence of specific imaging or laboratory abnormalities to guide the diagnosis. Notably, in most cases, peripheral neuropathy symptoms present before any overt signs of malignancy. Hence, accurately diagnosing PNS is imperative to expedite the detection of underlying malignancies and initiate timely cancer therapies.

Conclusions: While the prognosis for patients with paraneoplastic sensorimotor neuropathy remains complex, this case highlights the significance of early diagnosis and a multidisciplinary approach to care, involving neurology and hematology/oncology specialists. Increased awareness of PNS among healthcare providers may ultimately improve patient outcomes. Due to the high neurological morbidity and mortality associated with PNS, empiric immunomodulatory therapy should be considered before the medical evaluation is completed.