Differential Diagnosis for Severe Increased CMAP Latency with Normal Amplitude
- Single Most Likely Diagnosis
- Demyleinating Polyneuropathy: This condition, such as Guillain-Barré syndrome or chronic inflammatory demyelinating polyneuropathy (CIDP), is characterized by damage to the myelin sheath surrounding nerve fibers, leading to slowed nerve conduction velocities and increased latencies without significantly affecting the amplitude of the compound muscle action potential (CMAP) initially.
- Other Likely Diagnoses
- Diabetic Neuropathy: Although typically associated with axonal damage, the early stages or certain types of diabetic neuropathy can present with demyelinating features, including increased latency.
- Uremic Neuropathy: Uremia can cause a mix of demyelinating and axonal damage, potentially leading to increased latency with relatively preserved amplitude in the early stages.
- Toxic Neuropathy: Exposure to certain toxins can cause demyelination, resulting in increased latency with normal or near-normal amplitude.
- Do Not Miss Diagnoses
- Botulism: This condition can present with demyelinating features on electrophysiological studies due to its effect on the neuromuscular junction, and missing this diagnosis could be fatal.
- Lyme Disease: Neuroborreliosis, particularly in its early stages, can cause a demyelinating neuropathy, and prompt recognition is crucial for effective treatment.
- Rare Diagnoses
- POEMS Syndrome: A rare paraneoplastic syndrome that can cause demyelinating neuropathy among other systemic symptoms.
- Tangier Disease: A rare genetic disorder affecting lipid metabolism, which can lead to neuropathy with demyelinating features.
- Refsum Disease: A genetic disorder leading to the accumulation of a specific fatty acid, which can cause demyelinating neuropathy.