10. Neurophysiological profile of multifocal motor neuropathy. Issue 3 (March 2016) - Garg, Nidhi
Abstract : Introduction: Multifocal motor neuropathy (MMN) is a rare immune-mediated neuropathy, typically presenting with asymmetrical, and slowly progressive, distal upper limb wasting and weakness without sensory abnormalities. The disorder is associated with GM1 antibodies in approximately 50% of cases but the pathogenic role of such antibodies along with the mechanism of conduction block remains unclear. Methods: Nerve conduction studies and motor axonal excitability studies were undertaken in 7 patients with MMN (mean age: 52.3). Axonal excitability studies were undertaken in the median nerve at the wrist and compared to 70 healthy controls (mean age: 49.6). Results: When compared healthy controls, patients with MMN had greater threshold changes in threshold electrotonus in both depolarizing (TEd 90–100 ms: 54.09 ± 1.3 vs 45.0 ± 0.5; p < 0.01) and hyperpolarizing directions (TEh 90–100 ms: −157.7 ± 9.1 vs −117.8 ± 2.0; p < 0.01). In addition, they demonstrated greater superexcitability (−40.2 ± 2.1 vs −23.7 ± 0.7; p < 0.01) and reduced refractoriness at 2.5 msec (−6.7 ± 7.4 vs 28.2 ± 2.1; p < 0.01). Conclusion: Patients with MMN have a unique neurophysiological profile demonstrated on axonal excitability studies which are consistent with axonal hyperpolarization.