Clinical importance of F-waves as a prognostic factor in Guillain-Barré syndrome in children

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.

Clinical and Electrophysiological Factors Predicting Prolonged Recovery in Children with Guillain-Barré Syndrome

OBJECTIVE

To compare clinical and nerve conduction studies (NCS) parameters predictive of outcome in children with acute inflammatory demyelinating polyneuropathy (AIDP) and acute motor axonal neuropathy (AMAN).

METHODS

In this prospective observational study, NCS was done on all children at admission and repeated before discharge. Functional status of patients was graded as per Hughes Disability score. These children were followed up till they achieved independent walking. Clinical and NCS criteria were compared between (a) AMAN and AIDP and (b) two subgroups of children with AMAN-those who achieved early (within 60 d) versus delayed (i.e., after 60 d) walking.

RESULTS

Fifty-seven children were initially enrolled, first NCS showed inexcitable nerves in 10, AMAN in 29, acute motor-sensory axonal neuropathy (AMSAN) in 3, AIDP in 13, and 2 were normal. Subsequent NCS showed AMAN in 37, AIDP in 15, AMSAN in 3 patients. There were no deaths, 16 required ventilation. Follow-up till independent walking, was available for 40 patients. AMAN was associated with faster progression, greater peak disability, prolonged hospital stay, and delayed walking (p < 0.05). Asymmetrical nerve involvement predicted prolonged hospital stay as well as delayed walking. In the AMAN group, prolonged ulnar F-wave latencies were significantly associated with delayed walking (p = 0.02).

CONCLUSION

Long term prognosis of pediatric GBS is generally satisfactory. AMAN, asymmetric involvement and prolonged ulnar F-wave latencies in children with AMAN were associated with delayed walking.

Establishing Normal Values for F-Wave Latencies in Diagnosing Peripheral Neuropathies for the Pediatric Population

PURPOSE

We present a unique technique applying F-wave latencies to assist in the diagnosis of peripheral neuropathy within the pediatric age group.

METHODS

We calculated an F-wave estimated deviance adjusted for limb length measurements, distal motor conduction velocity, and distal motor latencies. We compared the F-wave estimated deviance from the normal subjects with those with peripheral neuropathy (both axonal and demyelinating) to establish diagnostic accuracy in pediatric patients.

RESULTS

The normal range for the F-wave estimated deviance in the upper limb was -1 to +6 ms and in the lower limb was -8 to +5 ms. When compared with 82 subjects with peripheral neuropathy, there was a significant difference between the normal subjects and those with neuropathy (P values between 0.002 and 0.0005 for each of the individual nerves tested).

CONCLUSIONS

The F-wave estimated deviance is independent of age and can be accurately applied to the electrodiagnostic testing of pediatric patients with suspected neuropathy.

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.

F wave, A wave, H reflex, and blink reflex

Late responses include F waves, A waves, H reflex, and the blink reflex. These responses help enhance routine nerve conduction studies. Despite the use of F waves in multiple clinical applications, their studies can technically challenge even the most experienced electromyographers. They vary in latency, amplitude, and configuration, whereas A waves show no change in latency or morphology. Electrical stimulation of the supraorbital branch of the trigeminal nerve on one side results in a reflexive activation of the facial nucleus causing contraction of the orbicularis oculi muscle, short latency R1 ipsilaterally, and long latency R2 bilaterally. F waves can help determine the presence of a polyneuropathy. A waves can reflect axonal damage. H reflexes provide nerve conduction measurements along the entire length of the nerve, demonstrating abnormalities in neuropathies and radiculopathies. Abnormalities in the blink reflex can suggest the presence of an acoustic neuroma or a demyelinating polyneuropathy, which can affect the cranial nerves. This reflex, which also needs appropriate technical expertise, helps to assess cranial nerves V and VII along with their connections in the pons and medulla. The blink reflex, the electrical version of the corneal reflex, represents a polysynaptic reflex.

Bickerstaff Brainstem Encephalitis and overlapping Guillain-Barré syndrome in children: Report of two cases and review of the literature

Bickerstaff Brainstem Encephalitis (BBE) is a rare autoimmune encephalitis, characterized by acute ophthalmoplegia, ataxia and altered state of consciousness. Together with Guillan-Barrè Syndrome (GBS) and Miller-Fisher Syndrome, it forms a spectrum of post-infectious demyelinating diseases. Overlapping forms between BBE and GBS (BBE/GBS) are described in patients with lower limbs weakness and typical signs of BBE, suggesting a combined involvement of Central and Peripheral Nervous System (PNS), but only few reported cases are focused on pediatric population. We reviewed all cases of pediatric BBE in the literature, to determine if any patient showed features suggestive for BBE/GBS. Data analysis focused on the diagnostic tests performed (e.g. anti-GQ1b antibodies), neuroimaging and nerve conduction studies (NCS). Further attention was given to the therapeutic management and to patients' outcome. We additionally present two previously unreported pediatric cases. Our review retrieved 19 cases of BBE/GBS, only 2 of which were originally and correctly diagnosed by the authors. The prevalence was higher in male subjects (ratio 3:1) and median age at diagnosis was 8 years. Anti-GQ1b were positive in 46% of the patients, while NCS were altered in 64%. Only 25% of the patients that underwent brain MRI showed abnormal findings. The incidence of BBE/GBS has been underrated in the past, mostly due to an underestimation of the PNS involvement. We therefore suggest to investigate all patients with a clinical picture suggestive of BBE/GBS through electroencephalogram, NCS, brain and spine MRI in order to promptly achieve the correct diagnosis.