To date there is no electrophysiological gold standard in defining the subtypes of GBS. Recovery of abnormal CMAP amplitude reduction and of conduction slowing, without development of temporal dispersion, has been described in AMAN and AMSAN and is considered related to the impairment of nodes of Ranvier, leading to a transient dysfunction of excitability.
The two main neurophysiological approaches to GBS are the serial studies approach (SSA) and the One Study approach (OSA). The former, sustained by the authors, showed 22-38% of patients had their GBS subtype changed by serial studies. The OSA however showed no differences in the overall frequencies of diagnostic subtypes at the second study. 1 Rajabally and colleagues2 proposed a different criteria set which showed similar frequencies of GBS subtypes and of patients changing classification in relation to previous reports, which applied serial recording approach, concluding that a single study might suffice for electro-diagnosis of GBS subtypes.
However, comparison of sparse linear discriminant analysis (SLDA), a supervised statistical classification method, with Hadden’s, Rajabally’s and Uncini’s criteria showed lower misclassification error rates for SLDA.3
The authors conclude the review recommending a second electrophysiological study, within 3–8 weeks from disease onset, in patients affected by GBS who show at first study low amplitude distal CMAPs, conduction block without temporal dispersion or in cases without clear demyelinating features. However, if such follow-up study is not feasible, the authors recommend application of Uncini’s or Rajabally’s criteria with additional analysis of temporal dispersion at first study.
- To date there is no electrophysiological gold standard in defining the subtype of GBS
- The two main neurophysiological approaches to GBS are the serial studies approach (SSA) and the One Study approach (OSA)
- A second electrophysiological study is recommended in patients with GBS who show at first study low amplitude distal CMAPs, conduction block without temporal dispersion or no clear demyelinating features. When this is not feasible, application of Uncini’s or Rajabally’s criteria at first study, with additional analysis of temporal dispersion, is recommended.
References:
1. Van den Bergh PYK, Piéret F, Woodard JL, Attarian S, Grapperon AM, Nicolas G, et al. Guillain-Barré syndrome subtype diagnosis: a prospective multicentric European study. Muscle Nerve 2018. https://doi.org/10.1002/mus.26056.
2. Rajabally YA, Durand MC, Mitchell J, Orlikowski D, Nicolas G. Electrophysiological diagnosis of Guillain-Barré syndrome subtype: could a single study suffice? J Neurol Neurosurg Psychiatry. 2015;86:115-119. doi: 10.1136/jnnp-2014-307815
3. Uncini A, Ippoliti L, Shahrizaila N, Sekiguchi Y, Kuwabara S. Optimizing the electrodiagnostic accuracy in Guillain-Barré syndrome subtypes: criteria sets and sparse linear discriminant analysis. Clin Neurophysiol 2017;128:1176–83.