Electrodiagnostic errors contribute to chronic inflammatory demyelinating polyneuropathy misdiagnosis

Introduction: Documentation of peripheral nerve demyelination is an important part of the chronic inflammatory demyelinating polyneuropathy (CIDP) diagnostic process. Methods: We performed a retrospective analysis of patients referred with a diagnosis of CIDP who were found to have a different condition. Electrodiagnostic study data and interpretations formulated at the time of the initial diagnosis were compared to those obtained during the reevaluation. Results: Thirty-nine of 86 patients were found not to have CIDP. Initial electrodiagnostic data quality was generally acceptable, but initial electrodiagnostic conclusions were confirmed in only 45% of misdiagnosed studies. Discussion: Vulnerability to interpretive errors increases when amplitude-dependent slowing occurs with length-dependent axonal neuropathies or motor neuron disease, amplitude-independent slowing occurs in diabetic patients, fibular nerve to extensor digitorum brevis (EDB) muscle findings are the focal diagnostic abnormality, conduction block is absent, conduction velocity (CV) slowing is limited to compressible sites, and accurate electrodiagnostic interpretations are dismissed in favor of equivocal clinical and cerebrospinal fluid findings. Muscle Nerve 57: 542–549, 2018.