Differential Diagnosis for Decreased Amplitude Lateral Antebrachial Nerve and Mild Neurogenic Changes
Single Most Likely Diagnosis
- Radial Neuropathy: This condition is characterized by damage to the radial nerve, which can lead to decreased amplitude in the lateral antebrachial nerve and mild neurogenic changes in muscles innervated by the radial nerve, such as the biceps, while sparing the triceps and extensor indicis proprius (EIP) which are also innervated by the radial nerve but at different levels.
Other Likely Diagnoses
- C7 Radiculopathy: This condition involves damage to the C7 nerve root, which can cause neurogenic changes in muscles innervated by the C7 root, including the biceps and flexor digitorum profundus (FDI), while potentially sparing the triceps and EIP due to their different innervation patterns.
- Brachial Plexopathy: Involvement of the brachial plexus, particularly affecting the posterior cord or the C7 root within the plexus, could lead to the observed pattern of nerve involvement, though it might be less common to see such a selective pattern.
Do Not Miss Diagnoses
- Amyotrophic Lateral Sclerosis (ALS): Although less likely, ALS is a critical diagnosis not to miss due to its severe prognosis. ALS can present with focal weakness and neurogenic changes in a variety of muscle groups, including those mentioned, and can mimic other neuropathies or radiculopathies in its early stages.
- Multifocal Motor Neuropathy (MMN): This is a rare condition characterized by asymmetric muscle weakness and atrophy, often with conduction block on nerve conduction studies. It can present with a pattern that might mimic the described neurogenic changes and should be considered to ensure appropriate treatment.
Rare Diagnoses
- Neuralgic Amyotrophy: Also known as Parsonage-Turner syndrome, this condition involves acute, severe pain and subsequent weakness and atrophy of the muscles around the shoulder and arm. It can affect various nerves, including the radial nerve, and might present with a similar pattern of involvement.
- Lyme Disease: In rare cases, Lyme disease can cause neuropathy, including radiculopathy or mononeuritis multiplex, which might present with a pattern of nerve involvement similar to what is described, though this would typically be accompanied by other systemic symptoms.