Acute Reversible Motor Predominant Polyradiculoneuropathy among Thai Prisoners after the Outbreak of H3N2 Influenza: A Case Series

Abstract

Objective: This study aims to describe the clinical, laboratory and electrophysiological findings of the prisoners who developed acute reversible motor predominant polyradiculoneuropathy after the outbreak of H3N2 influenza. Material and Methods: Among H3N2 infected Thai prisoners, all patients with acute flaccid weakness were included in this retrospective case series. We analyzed the results of electromyography (EMG), cerebrospinal fluid analysis, and serum levels of antiganglioside antibodies, folate, thiamine, and vitamin B12.Results: Among 262 H3N2 influenza patients, motor predominant polyradiculoneuropathy predominantly affecting the lower limbs developed in 10 patients. EMG revealed significantly decreased compound muscle action potentials with preserved distal latencies and conduction velocities in the peroneal nerves. Early fibrillation potentials were demonstrated on EMG performed 12-14 days post-onset of symptoms. The cerebrospinal fluid study showed normal profiles. All laboratory results appeared normal except for the significantly low mean±standard deviation serum folate level of 1.80± 0.78 [reference value 3.89–26.80 nanograms per milliliter (ng/mL)] as compared to the mean serum folate level in the normal Thai population of 10.80 ng/mL (p-value<0.001, 95% confidential interval -9.55 to -8.45). All patients were treated with 15 milligram per day of folic acid and all patients improved clinically. Conclusion: Although the relationship between low plasma folate level and polyradiculoneuropathy is unclear, a superimposed folate deficiency contributing to the pathophysiology is possible.