The diagnosis of CIDP can be challenging. Patients generally have both proximal and distal weakness on examination. Deep tendon reflexes are markedly reduced or absent. Distal sensory loss is often found on clinical examination. Electrodiagnostic studies are extremely important and typically show clear signs of demyelination, with prolonged distal and F-wave latencies and slow conduction velocities on nerve conduction studies. Conduction block and temporal dispersion of compound motor action potentials are common. Cerebrospinal fluid examination generally reveals significantly elevated spinal fluid protein without an increased white blood cell count. Nerve biopsy is almost never needed for diagnosis but, if performed, may demonstrate segmental demyelination and endoneurial and epineurial inflammation. Teased nerve fiber preparation may show features of demyelination and remyelination along individual nerve strands, and routine studies may show the presence of onion bulbs and inflammatory exudates.
The differential diagnosis of CIDP can be broad, but in most cases, the clinical and laboratory features point to the diagnosis without need for a large differential diagnosis. Diagnosis of CIDP becomes more complex in cases of late-stage CIDP, when there may be significant axonal injury found on electrodiagnostic studies, making it difficult to assess if the demyelinating or axonal component is primary. Diabetic polyneuropathy often shows mixed axonal and demyelinating features electrodiagnostically; some authors have described a form of “diabetic CIDP.” It remains controversial if diabetic CIDP is a true entity because epidemiologic studies have not found an increased rate of CIDP in diabetic patients. A rare condition called POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, skin changes) syndrome can present with a demyelinating polyradiculoneuropathy; this is often diagnosed when suspected CIDP patients are refractory to immunotherapy. POEMS is discussed later under “Monoclonal Protein–Associated Neuropathies.” Lymphoma can also manifest as a polyradiculoneuropathy and should be carefully considered if there are risk factors; CSF cytology and nerve biopsy can also be helpful diagnostically in cases where this is suspected. Immunoglobulin M (IgM) monoclonal gammopathy of undetermined significance (MGUS) neuropathy, another acquired demyelinating polyneuropathy, is discussed later under “Monoclonal Protein–Associated Neuropathies.”
Variants of CIDP include focal or multifocal forms, which are described by various names in the literature, including CIDM (chronic inflammatory demyelinating mononeuropathy), MADSAM (multifocal acquired demyelinating sensory and motor neuropathy) and CISP (chronic inflammatory sensory polyradiculopathy). In these less classic forms, diagnosis is more difficult, and sometimes magnetic resonance imaging and fascicular nerve biopsy can be helpful.
The treatment of CIDP is varied, and large clinical trials are limited. Patients are generally treated with immunomodulatory agents. There are three first-line treatments: oral or intravenous corticosteroids, intravenous immunoglobulin, and plasma exchange. Controlled trials have shown these agents to be effective. Oral steroid-sparing immunomodulatory agents are often used, without good comparative data for their relative efficacy. The treatment of CIDP is very effective; without treatment many patients will need aids to walk or will be wheelchair confined. With treatment, many can lead essentially normal lives. In general, longterm treatment with some type of immunosuppressive drug is required, because this is a chronic condition.
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