The electrophysiologic test results and the MRI scans support a diagnosis of lumbosacral radiculoplexus neuropathy (LRPN). Contrast enhancement in the cauda equina and active denervation potential in the paraspinal muscles are consistent with nerve root inflammation. Contrast enhancement in the lumbosacral plexus and reduced lower-extremity sensory response support involvement of the peripheral nerves and plexus. The absence of demyelinating features on the electrodiagnostic study and the normal upper-extremity study argue against chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). The negative cytology, normal MRI scans of the brain and spine, and normal CSF cell count make meningeal carcinomatosis unlikely. Because pain is a predominant symptom in this patient, radiation-induced lumbosacral plexopathy is less likely.
Additional serum and CSF studies were obtained and revealed elevated glial fibrillary acidic protein (GFAP) antibodies, with a titer of 1:1920 in the serum. MRI scans of the chest, abdomen, and pelvis demonstrated diffuse wall thickening of the urinary bladder, an ill-defined soft tissue mass around the rectum (Figure 2), and left supraclavicular adenopathy. A biopsy of the supraclavicular lymph node was positive for metastatic squamous cell carcinoma (Figure 3). A biopsy of the bladder showed only fibrotic tissue. A biopsy of the soft-tissue mass with chemical analysis confirmed a bladder origin.
Additional testing confirmed that the patient's progressive decline resulted from paraneoplastic LRPN associated with GFAP antibody. LRPN is an immune-mediated neuropathy that presents with asymmetric radicular pain, followed by weakness in the corresponding region as well as sensory loss. Over time, it spreads to the opposite limb.[1,2]
Clinical examination reveals asymmetric proximal and distal weakness and sensory loss, with reduced lower-extremity reflexes. Significant weight loss is common.[1,2,3,4] Nerve conduction studies and electromyography demonstrate reduced sensory and motor responses, as well as active denervation changes that span multiple nerve roots.[2,3,4] Nerve pathologic findings show axonal degeneration with associated microvasculitis, ischemic changes, and inflammatory cells. Serum and CSF studies demonstrate upregulation of inflammatory markers, which supports an inflammatory etiology.[3,5,6,7,8]
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Cite this: Xuan Kang. Neurology Case Challenge: A Man With Buttocks Pain, Bladder and Bowel Incontinence - Medscape - Jul 21, 2022.