Subacute Motor Neuron Hyperexcitability with Mercury Poisoning: A Case Series and Literature Review

Abstract

Motor neuron hyperexcitability (MNH) indicates a disorder characterized by an ectopic motor nerve discharge on electromyogram (EMG). Here, we present a series of three cases of subacute MNH with mercury poisoning. The first case showed hyperhidrosis, insomnia, generalied myokymia, cramps, tremor, weight loss, and myokymic and neuromyotonic discharges, followed by encephalopathy with confusion, hallucinations, and memory decrease. The second case was similar to the former but without encephalopathic features. The third case showed widespread fasciculation, fatigue, insomnia, weight loss, and autonomic dysfunction, including constipation, micturition difficulty, and impotence, with multiple fibrillation, unstable fasciculation, widened motor neuron potential, and an incremental response at high-rate stimulation in repetitive nerve stimulation. Based on the symptoms, the three cases were diagnosed as Morvan's syndrome, Isaacs' syndrome, and Lambert-Eaton myasthenic syndrome with ALS-like syndrome, respectively. Mercury poisoning in the three cases was confirmed by analysis of blood and urine samples. All cases recovered several months after chelation therapy and were in good condition at follow-up. Very few cases of MNH linked with mercury exposure have been reported in the literature. The mechanism of mercury-induced MNH may be associated with ion channel dysfunction.

Healing of Amyotrophic Lateral Sclerosis: A Case Report

“…There are reports in the literature showing that chelation therapy is capable of reducing ALS or ALS-like symptoms after exposure to mercury [20], but there are also cases without success [21]. The chelation therapy applied here is different from earlier approaches.…”

Mercury toxicity following unauthorized siddha medicine intake – A mimicker of acquired neuromyotonia - Report of 32 cases

“…[ 17 ] A large number of case reports and case series analysis are available in the world literature about the association of native medicines intake or heavy metal poisoning with neuromyotonia like presentation. [ 18 19 20 ]…”

“…Zhou et al . reported[ 18 ] three cases of mercury poisoning associated with motor nerve hyperexcitability; two of these three cases also had encephalopathic features. Panagariya et al .…”

Peripheral nerve hyperexcitability following titanium marker placement

“…[2][3][4][5][6] The mechanism of PNH in these cases is typically due to toxicity resulting in ion channel dysfunction or acetylcholinesterase inhibition. [2][3][4][5][6] Titanium is used extensively in surgical and radiological procedures due to its sustainability and biocompatible properties. It has been demonstrated that titanium may alter the kinetics of voltage-gated potassium channel currents resulting in changes in neuron excitability.…”