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The correlation between the change of distal motor latency of the median nerve and the abundant A-waves in Guillain-Barré syndrome
  1. Akiko Kadoya1,2,
  2. Go Ogawa1,
  3. Shingo Kawakami1,3,
  4. Isao Yokota4,
  5. Yuki Hatanaka1,
  6. Ayumi Uchibori5,
  7. Atsuro Chiba5,
  8. Masahiro Sonoo1
  1. 1 Department of Neurology, Teikyo University School of Medicine, Itabashi, Tokyo, Japan
  2. 2 Division of Neurology, Department of Internal Medicine, National Defense Medical College, Tokorozawa-shi, Saitama, Japan
  3. 3 Department of Neurology, Omori Red Cross Hospital, Ota-ku, Tokyo, Japan
  4. 4 Department of Biostatistics, Graduate School of Medicine, The University of Tokyo, Bunkyo, Tokyo, Japan
  5. 5 Department of Neurology, Kyorin University School of Medicine, Mitaka-shi, Tokyo, Japan
  1. Correspondence to Dr Go Ogawa, Department of Neurology, Teikyo University School of Medicine, Kaga 2-11-1, Itabashi-ku, Tokyo 1738605, Japan; cqw17450{at}nifty.com

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Introduction

A-waves are intermediate components that are observed between the compound muscle action potential (CMAP) and the F-waves. We recently suggested that abundant A-waves in Guillain-Barré syndrome (GBS) can be a novel marker of demyelination because they were strongly correlated with the acute inflammatory demyelinating polyneuropathy (AIDP) subtype and the absence of anti-glycolipid antibodies.1

Hiraga et al 2 reported that patients with AIDP without anti-ganglioside antibodies showed progressive prolongation of the distal motor latency (DML) of the median nerve, whereas the DML of patients with AIDP with anti-ganglioside antibodies may initially be prolonged but rapidly return to normal, suggesting an essentially axonal pathology. These results imply the possibility that the time course of DML of the median nerve (median DML) can be used as another marker of demyelination.

In this report, we reanalysed the data collected in our previous study1 and compared the A-waves with other parameters, using the time course of the median DML as a gold standard.

Methods

The data of 30 patients with GBS (21 men and 9 women, 43.7±19.5 years old) were reanalysed. The abundant A-waves were defined as three or more identifiable peaks between the CMAP and F-waves, observed in the median or ulnar nerves at least once during weeks 3–6 from onset.1 Clinical features of patients with abundant A-waves were compared with those without.

Patients were classified into two groups using three different criteria, which were already determined in the preceding study.1 The first criterion was the abundant A-waves, which were positive in 9 and negative in 21patients. The second was Ho's criteria,3 applied …

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