Are electrophysiological features related to disability in patients with anti-MAG neuropathy?

Abstract

Objectives: To explore clinical-neurophysiological correlations in anti-myelin-associated glycoprotein (anti-MAG) neuropathy.

Methods: Clinical and electrophysiological data of 42 patients with anti-MAG neuropathy were retrospectively analysed. Disability was evaluated using the Overall Neuropathy Limitation Scale (ONLS), motor impairment through MRC sum score and sensory deficiency through INCAT sensory score. Compound motor action potential (CMAP) sum score was calculated adding the distal CMAP amplitude of the median, ulnar, tibial and fibular nerves of both sides.

Results: In multivariate analysis, motor impairment was associated with CMAP sum score (r=0.35, P=0.047) and distal motor latency in the median nerves (r=-0.45 P=0.012), sensory deficiency was related to motor conduction velocity in the median nerve (r=-0.65. P=0.02). Disability was correlated with CMAP sum score (r=-0.37, P=0.022).

Conclusion: Electrophysiological features are associated with clinical involvement in anti-MAG neuropathy. Reduction of CMAP amplitudes reflects distal motor latency delay and is mainly due to axonal loss. Since it is related to muscle weakness and disability, CMAP sum score may be a good marker in the evaluation of patients with anti-MAG neuropathy.

Keywords: Anti-MAG neuropathy; CMAP sum score; Disability; Incapacité fonctionnelle; Indice de latence distale; Myelin-associated glycoprotein (MAG); Neuropathie à anticorps anti-MAG; Overall Neuropathy Limitation Scale (ONLS); Somme des amplitudes motrices; Terminal latency index.