S6-1. Electrodiagnosis of Guillain-Barré syndrome

Abstract

Electrodiagnostic methods (EDx), including nerve conduction studies (NCSs), play an important role in the diagnosis of Guillain-Barre syndrome (GBS). It has a merit that the results are known immediately, which is an advantage over antibodies, another prevalent diagnostic measure, whose results are usually known after a few weeks. Consequently, treatment of GBS is usually started based on NCS results, as well as on neurological evaluation. High sensitivity, even in the disease onset, is another advantage of NCSs over antibodies: the sensitivity of the latter is 50–60%. Historically, NCS features of GBS have been believed to be demyelination. However, axonal variant (AMAN) was discovered in 1990s, and EDx of this subtype was extensively studied in Japan, especially by Kuwabara and colleagues. Their important finding was that AMAN may show certain “demyelinating” features such as prolonged distal motor latency (DML) or conduction block in the early stage of clinical course, which rapidly resolve, usually within 2 weeks. In this regard, serial NCS examination is necessary to accurately determine the EDx subtype of GBS. We added abundant A-waves as a feature characterizing AIDP. Maximal DML of the median nerve after 2 weeks was another single determinant discriminating AMAN and AIDP.