Can Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) present with features of axonal neuropathy on nerve conduction studies?

Can CIDP Present with Axonal Neuropathy on Nerve Conduction Studies?

Yes, Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) can present with features of axonal neuropathy on nerve conduction studies, particularly in atypical forms of CIDP. 1

Understanding CIDP and Its Electrodiagnostic Patterns

CIDP is traditionally characterized as a demyelinating polyneuropathy, but its presentation can be more complex:

• While classic CIDP shows predominantly demyelinating features on nerve conduction studies, atypical forms may present with significant axonal involvement 1
• Nerve biopsy is considered useful in evaluating atypical forms of CIDP, suggesting that these variants may have distinctive pathological features that differ from typical presentations 1
• The American Academy of Neurology recognizes that CIDP can have varied electrodiagnostic patterns, making diagnosis challenging in non-classic presentations 1

Evidence for Axonal Features in CIDP

Several clinical observations support the existence of CIDP variants with axonal features:

• Some patients with CIDP may show a pattern consistent with axonal polyneuropathy on initial nerve conduction studies 2
• There are documented cases of steroid-responsive axonal polyneuropathies that may represent one extreme of the CIDP spectrum 2
• The term "chronic inflammatory polyneuropathy" has been suggested to encompass cases ranging from pure demyelinating to pure axonal neuropathies that respond to immunomodulatory treatment 2

Distinguishing Features from Other Neuropathies

When evaluating potential CIDP with axonal features, consider these distinguishing characteristics:

• CIDP typically shows more uniform slowing of nerve conduction compared to other demyelinating neuropathies like POEMS syndrome, which shows more predominant slowing in intermediate nerve segments 3
• Conduction block is common in typical CIDP (found in approximately 44% of tested nerves) but may be rare in atypical forms or those with predominant axonal features 3
• Pure motor CIDP variants have been described that maintain demyelinating features without sensory involvement over long periods, suggesting specific immunological processes rather than random inflammation 4

Diagnostic Approach for Suspected CIDP with Axonal Features

When axonal features are present on nerve conduction studies but CIDP is suspected:

• Consider nerve biopsy in patients with atypical presentations, as this may help establish the diagnosis 1
• Look for other supportive features of CIDP such as elevated CSF protein, which is present in most but not all cases 2
• Evaluate for response to immunomodulatory therapy, as treatment responsiveness can be a diagnostic clue in cases with atypical electrodiagnostic findings 2

Treatment Implications

The recognition of axonal variants of CIDP has important treatment implications:

• Patients with predominantly axonal features who might otherwise be diagnosed with chronic idiopathic axonal neuropathies may respond to immunomodulatory treatments 2
• Some axonal variants may be steroid-responsive despite not meeting classic electrodiagnostic criteria for CIDP 2
• Intravenous or subcutaneous immunoglobulin has demonstrated efficacy in CIDP, including in some patients with atypical presentations 5

Common Pitfalls in Diagnosis

To avoid misdiagnosis when evaluating potential CIDP with axonal features:

• Relying solely on electrodiagnostic criteria may lead to underdiagnosis of CIDP variants with predominant axonal features 6
• At least 16 different sets of electrodiagnostic criteria for CIDP have been proposed, reflecting the challenge in capturing all presentations of this condition 6
• The complexity of formal CIDP diagnostic criteria makes them difficult to apply in clinical practice, potentially leading to missed diagnoses of atypical forms 6

In conclusion, while CIDP is classically considered a demyelinating neuropathy, axonal features can be present, especially in atypical forms. Recognizing these variants is crucial for appropriate treatment, as they may respond to immunomodulatory therapies despite not meeting traditional electrodiagnostic criteria for demyelination.