Differential Diagnosis

• Single most likely diagnosis
  • Chronic Inflammatory Demyelinating Polyneuropathy (CIDP): The presence of cauda equina enhancement, sciatic nerve enlargement, elevated CSF protein, and motor axonal neuropathy on nerve conduction studies are all consistent with CIDP, particularly the Lewis-Sumner variant, which is characterized by multifocal involvement and asymmetric onset.
• Other Likely diagnoses
  • Multifocal Motor Neuropathy (MMN): Although MMN typically presents with pure motor involvement and conduction block, some cases may have elevated CSF protein and could be considered in the differential diagnosis.
  • Neuropathy associated with IgM Monoclonal Gammopathy: This condition can present with demyelinating neuropathy and elevated CSF protein, but the presence of cauda equina enhancement and sciatic nerve enlargement might be less common.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Malignant nerve root infiltration (e.g., lymphoma, leukemia): Although less likely, malignant infiltration of the nerve roots could present with similar imaging findings and elevated CSF protein, making it a critical diagnosis not to miss due to its severe implications.
  • Infectious radiculitis (e.g., Lyme disease, HIV): Certain infections can cause radiculitis and neuropathy, and although less common, they are important to consider due to their potential for serious consequences if left untreated.
• Rare diagnoses
  • Neurosarcoidosis: This condition can cause neuropathy and elevated CSF protein, but the presence of cauda equina enhancement and sciatic nerve enlargement would be unusual.
  • POEMS syndrome: A rare multisystem disorder that can cause demyelinating neuropathy, but it typically presents with other systemic features such as organomegaly, endocrinopathy, and monoclonal gammopathy.