Dynamics of Nerve Conduction Studies in Patients With Guillain–Barré Syndrome

Introduction/Aims: The value of electrodiagnostic subtyping of Guillain–Barré syndrome (GBS) is still debated. This study aimed to determine the diagnostic yield, timing, and changes of the electrodiagnostic subtyping in patients with GBS in serial nerve conduction studies (NCS). Methods: Data were extracted from the International GBS Outcome Study (IGOS) database. Serial NCS were available for 469 patients. For the serial NCS analysis, the intervals between the first and second study were defined as ≥ 7 and ≤ 42 days after onset of weakness. All NCS were classified according to the electrodiagnostic criteria sets of Hadden et al. and Rajabally et al. Results: In NCS conducted within 3 days of onset of weakness, an axonal or demyelinating subtype could be demonstrated in 58.4% (Hadden) and 52.1% (Rajabally). NCS performed at a later timepoint demonstrated a similar yield of axonal and demyelinating subtypes. In patients with motor-sensory and motor GBS, the electrodiagnostic subtype changed on serial NCS in 37.8% (Hadden) and 44.7% (Rajabally). As the subtypes changed in multiple and opposite directions, the total proportion of axonal and demyelinating subtypes remained stable across time points. In patients with motor GBS, both axonal and demyelinating subtypes were found. Discussion: This study demonstrates the highly dynamic disease course of GBS. The role of NCS remains to support the clinical diagnosis of GBS and should be performed as quickly as possible after onset of weakness. If these early NCS are non-diagnostic, repeating the study should be considered. Electrodiagnostic subtyping offers no additional value.