Differential Diagnosis for Decreased Sural Snap, Conduction Block Tibial CMAP with Normal SPE and Peroneal
- Single Most Likely Diagnosis
- Guillain-Barré Syndrome: This condition is characterized by rapid-onset muscle weakness caused by the immune system damaging the peripheral nervous system. The presence of conduction block in the tibial nerve with normal sensory nerve action potentials (SNAPs) like the sural nerve, and involvement of motor nerves (indicated by decreased CMAP) fits with the diagnosis, although the pattern can vary.
- Other Likely Diagnoses
- Chronic Inflammatory Demyelinating Polyneuropathy (CIDP): Similar to Guillain-Barré Syndrome but with a more chronic course, CIDP can present with conduction blocks and mixed sensory and motor nerve involvement.
- Multifocal Motor Neuropathy (MMN): Characterized by asymmetric muscle weakness and wasting, MMN often presents with conduction blocks in motor nerves, which could explain the tibial CMAP findings.
- Do Not Miss Diagnoses
- Lyme Disease: Although less common, Lyme disease can cause neuropathy, including radiculoneuropathy or mononeuropathy multiplex, which might present with focal nerve conduction abnormalities.
- Vasculitic Neuropathy: Conditions like polyarteritis nodosa or granulomatosis with polyangiitis can cause mononeuropathy multiplex, presenting with asymmetric nerve involvement and conduction blocks.
- Rare Diagnoses
- POEMS Syndrome: A rare paraneoplastic syndrome associated with a plasma cell disorder, characterized by polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, and skin changes. The neuropathy can present with demyelinating features.
- Tangier Disease: A rare genetic disorder affecting lipid metabolism, leading to neuropathy among other symptoms. The neuropathy can be multifocal and presents with features of demyelination and remyelination.