Allen JA and Lewis RA. Neurology 2015;85:498-504
Submitted by Zaeem A. Siddiqi, MD, PhD & Andrew W. Tarulli, MD, News Science Editorial Board
Clinical and electrodiagnostic data of 58 patients with a diagnosis of CIDP referred to a single center over a 1.5-year period were reviewed. Only 53% of patients met European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) criteria for CIDP. Therefore, 47% of patients were diagnosed with “not-CIDP”. After careful evaluation, the most commonly identified of the 16 alternative diagnoses for the not-CIDP patients were diabetic polyneuropathy, amytrophic lateral sclerosis, fibromyalgia, and idiopathic small-fiber neuropathy. Cerebrospinal fluid elevations were mild in the not-CIDP group, measuring greater than 100 mg/DL in only 2 of 20 patients, as compared to 17 of 31 in the patients with CIDP. Slowed conduction velocities were identified frequently in the not-CIDP patients, though usually in association with reduced CMAP amplitudes or co-existing with another neuropathic condition such as diabetic polyneuropathy. Patients with not-CIDP were treated with IVIg for an average of 1.5 years. Of these patients, 85% reported a subjective improvement. Of the four not-CIDP patients who demonstrated objective improvement in strength with immunotherapy, the ultimate diagnoses were multifocal motor neuropathy, multiple sclerosis, neurosarcoidosis, and stiff-person syndrome.
Comment: This is an important study, as it demonstrates the troubling frequency with which patients are misdiagnosed with CIDP and even treated with immunotherapy. Neuromuscular subspecialty referral and closer adherence to published guidelines would reduce this problem considerably, though likely not eliminate it. The report of subjective improvement in 85% of patients without CIDP is striking, and is likely comprised of (1) a large placebo component and (2) treatment of other immune-mediated conditions. Despite the temptation to treat patients to achieve a subjective improvement, this approach should be avoided.
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