From the Guidelines
Nerve conduction studies and electromyography in patients with granulomatosis with polyangiitis (GPA) may reveal findings consistent with peripheral nerve involvement, typically showing evidence of mononeuritis multiplex or polyneuropathy. These tests are crucial in assessing the extent of nerve damage and guiding treatment decisions, as outlined in the 2021 American College of Rheumatology/Vasculitis Foundation guideline for the management of antineutrophil cytoplasmic antibody-associated vasculitis 1.
Key Findings
- Nerve conduction studies often demonstrate asymmetric, multifocal sensory and motor axonal damage with reduced compound muscle action potential (CMAP) amplitudes and sensory nerve action potential (SNAP) amplitudes in affected nerves.
- Electromyography may show denervation potentials such as fibrillations, positive sharp waves, and complex repetitive discharges in affected muscles, along with reduced recruitment patterns and large motor unit potentials in chronic cases.
- A more symmetric polyneuropathy pattern may be observed in some GPA patients.
Clinical Implications
These neurophysiological findings reflect the vasculitic process in GPA that affects the vasa nervorum, leading to ischemia and axonal degeneration of peripheral nerves. The severity and distribution of these findings correlate with the extent of vasculitic nerve damage and can help monitor disease progression and response to immunosuppressive therapy, such as rituximab (RTX) or cyclophosphamide (CYC) for remission induction, and methotrexate (MTX) or azathioprine (AZA) for remission maintenance 1.
Treatment Considerations
The choice of treatment should be based on the patient's clinical condition, values, and preferences, with consideration of the potential benefits and risks of each therapy, as outlined in the guideline 1.
From the Research
Nerve Conduction Studies and Electromyography in Granulomatosis with Polyangiitis
- There is limited information available on the specific changes in nerve conduction studies and electromyography in patients with granulomatosis with polyangiitis (GPA) 2, 3, 4, 5, 6.
- However, it is known that GPA can cause mononeuritis multiplex, which is a form of vasculitis that affects the nerves 6.
- Mononeuritis multiplex can lead to abnormalities in nerve conduction studies and electromyography, such as conduction velocity slowing, amplitude reduction, and denervation changes 6.
- The diagnosis of GPA relies on a combination of clinical findings, imaging study results, laboratory test results, serologic markers, and histopathologic results, but nerve conduction studies and electromyography may be useful in evaluating the extent of nerve involvement 6.
- Treatment strategies for GPA involving immunosuppression and adjuvant therapies may improve the prognosis, but the specific effects on nerve conduction studies and electromyography are not well documented 2, 3, 4, 5.