Clinical Significance of A Waves in Acute Inflammatory Demyelinating Polyradiculoneuropathy

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.

The Presence and Significance of A-Waves-A Retrospective Review of 679 Patients

PURPOSE

A-waves are late responses that have been reported in healthy individuals and patients with neurologic conditions. The mechanism(s) responsible for their generation and their clinical significance are not fully understood. The aim was to better characterize A-waves.

METHODS

A retrospective study was conducted in a high-volume Neurophysiology Department in a tertiary hospital in Melbourne, Australia. Consecutive neurophysiological tests including F-wave studies performed between July 2017 and September 2018 were reviewed to identify A-waves. Patients' characteristics and neurophysiological diagnoses were recorded.

RESULTS

A total of 679 patients were included in the analysis and a total of 2,730 nerves were studied. A-waves were most commonly found in tibial nerves, followed by peroneal, median, and ulnar nerves. A-waves were seen in 39.4% of individuals with otherwise normal nerve conduction studies and 39.1% of individuals with entrapment neuropathy. They were most seen in demyelinating neuropathy (85.7%), followed by mixed neuropathy (73.3%), anterior horn cell disease (66.7%), axonal neuropathy (61.2%), and radiculopathy (53.1%). Most patients with demyelinating neuropathy had multiple A-waves (61.9%), but these were also seen in 15.2% of individuals with otherwise normal nerve conduction studies and in 40% of those with other neurologic conditions. A-waves were more often seen in individuals older than 60 years.

CONCLUSIONS

A-waves are commonly seen in symptomatic individuals with otherwise normal nerve conduction studies and individuals with various neurologic conditions but are more commonly found in nerves with otherwise abnormal electrophysiological testing. A-waves are most seen in tibial nerves. Multiple A-waves were more commonly seen in demyelinating neuropathy than other conditions.

Characteristics of A-waves in patients with amyotrophic lateral sclerosis (ALS) versus demyelinating neuropathies (DN)

Objective

Detect the occurrence and characteristics of A-waves in amyotrophic lateral sclerosis (ALS) and demyelinating neuropathies (DN).

Methodology

Nerve conduction studies (NCS) of 28 patients (14 patients with ALS and 14 patients with DN) were reanalyzed to look for A-waves.

Results

We studied 61 nerves of the ALS group and 64 nerves of DN. In the ALS group, A-waves were detected in 21 nerves out of 61 nerves (34.4%). In the DN group, A-waves were recorded from 25 nerves out of 64 nerves (39%). In the DN group, A-waves were detected more often in nerves of upper extremities than lower extremities (out of a total of 25 nerves with A-waves, 18 median and ulnar nerves showed A-waves (72%) and that was statistically significant (P = 0.0021)). Complex A-waves (CAWs) occurred exclusively in patients with DN.

Conclusion

Most of the A-waves in the DN group were recorded more frequently from nerves of the upper extremities than those from lower extremities. CAWs occurred only in DN.

Significance

CAW seems to be a useful specific electrodiagnostic tool to distinguish DN from ALS.

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

INTRODUCTION

The "A" wave is a compound action potential evoked consistently from a muscle by submaximal electric stimulation to the nerve. "A" waves were usually associated with the presence of conduction block and abounded in lower limbs more than in upper limbs. Guillain Barre syndrome is an autoimmune polyradiculoneuropathy that usually follows respiratory or gastrointestinal infections.

PURPOSE

To study the prognostic value of "A" waves in patients with Guillain Barre syndrome with different recovery patterns.

METHODS

In this study, 50 patients with GuillainBarreSyndrome were enrolled. They were divided into two groups based on the presence or absence of "A" waves in their neurophysiologic study at onset of illness. Strength of limb muscles of the involved patients was assessed at onset of the study and 6 weeks later (short-term clinical recovery) using the Medical Research Council Scale.

RESULTS

Patients with waves (29 patients: 58%) showed poorer short-term follow-up parameters than those without "A" waves (21 patients: 42%).

CONCLUSIONS

Presence of "A" waves is usually associated with conduction block and marked degree of demyelination. "A" waves carry poor prognostic value in short-term follow-up parameters in patients with Guillain Barre syndrome.