Prognostic Value of "A" Waves in Patients With Guillain Barre Syndrome

Identical late motor responses in early Guillain-Barré syndrome: A-waves and repeater F-waves

Electrodiagnostic (EDx) studies play a key role in the investigation of suspected Guillain-Barré syndrome (GBS), providing diagnostic and prognostic information. However, initial EDx findings may not fulfill the neurophysiological criteria for the disease. The aim of this study was to estimate the occurrence and characteristics of A-waves and repeaters F-waves (Freps), both late motor responses identical in latency and configuration, in early stages of GBS. We retrospectively analyzed the initial nerve conduction study (NCS) of 26 GBS patients performed within 10 days from symptom onset. The final subtype diagnosis was acute inflammatory demyelinating polyneuropathy (AIDP) in 16 patients (six met the criteria at the initial EDx study and 10 at follow-up) and acute motor axonal neuropathy (AMAN) in 10 patients (six initially). Identical late responses were commonly found in the majority of nerves (84%). A-waves were present in 59% and an increased frequency of Freps was calculated in 61% of the 105 studied nerves. A-waves morphology (single or complex) could not distinguish between AIDP and AMAN. Nerves with normal NCS had a significantly higher frequency of A-waves, either isolated or in combination with increased index total Freps, as compared to nerves with low compound muscle action potential (CMAP) amplitudes or conduction block. Our findings suggest that both late responses can be useful as early markers of conduction changes of various pathophysiology, being frequently present even prior to abnormalities of CMAP parameters.

A-waves are associated with neuropathic pain in leprosy

INTRODUCTION/AIMS

The A-wave is a late response related either to demyelination or early axonal regeneration. It may be helpful in the evaluation of some peripheral neuropathies. In leprosy, previous studies suggested that A-waves could be a neurophysiological marker of pain in patients during reactions. Herein we have attempted to further assess the profile and clinical correlates of A-waves by exploring a large leprosy cohort.

METHODS

Between 2015 and 2018, 63 patients with leprosy (47 men and 16 women) had A-waves in nerve conduction studies and were included in this study. We included patients regardless of whether they were experiencing leprosy reactions or not. We then compared clinical features in nerves with and without A-waves.

RESULTS

The mean age of study participants was 46.5 ± 12.3 years and most had borderline leprosy. From this cohort, we assessed separately 83 motor nerves that demonstrated A-waves (group A⁺ ) and 29 motor nerves that did not demonstrate A-waves (group A^- ). Neuropathic pain (NP) was found in 66 of 83 nerves in group A⁺ , but only 5 of 29 in group A^- (79.5 vs 17.2%, P < .001). In contrast, no significant between-group difference emerged regarding presence of reactions, sensory function (based on Semmes-Weinstein evaluations), or muscle strength. A-waves were found in nerves with neuropathic pain experiencing (39 of 66 = 59%) or not experiencing (27 of 66 = 41%) leprosy reactions.

DISCUSSION

These results show that A-waves are associated with neuropathic pain in leprosy patients, regardless of the nerves affected and the immune status (in reaction or not).

Association Between A-Waves and Outcome in Pediatric Guillain-Barré Syndrome

Introduction

To examine the importance of abundant A-waves in electrophysiological classification and prognosis of pediatric Guillain-Barré Syndrome (GBS).

Methods

A single-center and retrospective study enrolling 65 children-patients, aged 16 years and younger, with clinically diagnosed GBS between 2013 to 2020. Hughes grade was used to assess functional disability at nadir, 1 month, and 6 months after symptom onset. Patients were divided into 2 groups according to the presence of abundant A-waves. Clinical features and prognosis between the 2 groups were compared.

Results

The distal motor latency of the median nerve in patients with GBS with A-waves (9.18 ms) was more prolonged than that of patients with GBS without A-waves (4.1 ms). An electrophysiological variant of these two groups was also statistically different (p = 0.006). The short-term prognosis of patients with AIDP with A-waves was worse than patients with AIDP without A-waves (χ² = 5.022, p = 0.025), and univariable logistic regression analysis showed statistically significant (OR: 5.844, 95% CI 1.118–30.553; p = 0.036).

Conclusion

A-waves were strongly associated with demyelination and poor short-term prognosis of AIDP in children. We proposed an electrophysiological marker for early prediction of outcome in the AIDP subtype of GBS, applicable for clinical practice and future treatment administration.