Poster 22: Monoclonal Gammopathy of Unknown Significance as a Cause of Noncompressive Radiculopathy: A Case Report

Abstract

Setting: Tertiary care cancer hospital. Patient: A 59-year-old woman with history of monoclonal gammopathy of unknown significance (MGUS) and right-sided breast cancer status post lumpectomy, chemotherapy, and radiation. Case Description: The patient presented with a 2-year history of bilateral burning, numbness, and tingling in the soles of her bilateral feet and toes with left greater than right. She denied any low back pain, weakness, or bowel and bladder changes. Manual muscle testing demonstrated 5/5 strength throughout bilateral upper and lower extremities. All reflexes were 2+ and symmetric bilaterally. Sensation was intact to light touch, proprioception, thermal perception, and pinprick throughout. Magnetic resonance imaging of the lumbar spine demonstrated minimal early degenerative changes without central or neuroforaminal stenosis. Nerve conduction studies exhibited normal motor and sensory nerve amplitude, distal latency, and conduction velocities. F waves were normal except for a minimally prolonged left tibial F-response latency. Electromyography revealed fibrillation potentials and positive sharp waves in the left tibialis anterior and centered on paraspinal muscles innervated by L5. Polyphasic motor units with increased amplitude and duration were noted in the left tibialis anterior. Needle electromyography was normal elsewhere. Laboratory evaluation, including complete blood count, antinuclear antibody, erythrocyte sedimentation rate, rheumatoid factor, C-reactive protein, vitamin B12, glycosylated hemoglobin, cryoglobulins, and Lyme titers, were all negative. Assessment/Results: MGUS associated noncompressive radiculopathy. Discussion: MGUS is a common cause of chronic idiopathic demyelinating polyradiculoneuropathy (CIDP). Noncompressive radiculopathy is a component of CIDP and can exist in isolation from other peripheral nervous system dysfunction, in part due to anatomic and physiologic differences in the nerve root as well as the potentially vasculitic nature of CIDP. Conclusions: Noncompressive radiculopathy can be seen as a component of MGUS associated CIDP and can exist without electrophysiologic evidence for neuropathy.