TY - JOUR
T1 - Excitability of motor and sensory axons in multifocal motor neuropathy
AU - Kovalchuk, Maria O
AU - Franssen, Hessel
AU - van den Berg, Leonard H
AU - van Schelven, Leonard J
AU - Sleutjes, Boudewijn T H M
N1 - Funding Information:
This project was supported by the European Federation of Neurological Societies scientific Fellowship and grant W.OR14-07 from the Prinses Beatrix Spierfonds .
Publisher Copyright:
© 2020 International Federation of Clinical Neurophysiology
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2020/11
Y1 - 2020/11
N2 - OBJECTIVE: To assess excitability differences between motor and sensory axons of affected nerves in patients with multifocal motor neuropathy (MMN).METHODS: We performed motor and sensory excitability tests in affected median nerves of 20 MMN patients and in 20 age-matched normal subjects. CMAPs were recorded from the thenar and SNAPs from the 3rd digit. Clinical tests included assessment of muscle strength, two-point discrimination and joint position.RESULTS: All MMN patients had weakness of the thenar muscle and normal sensory tests. Motor excitability testing in MMN showed an increased threshold for a 50% CMAP, increased rheobase, decreased stimulus-response slope, fanning-out of threshold electrotonus, decreased resting I/V slope, shortened refractory period, and more pronounced superexcitability. Sensory excitability testing in MMN revealed decreased accommodation half-time and S2-accommodation and less pronounced subexcitability. Mathematical modeling indicated increased Barrett-Barrett conductance for motor fibers and increase in internodal fast potassium conductance for sensory fibers.CONCLUSIONS: Excitability findings in MMN suggest myelin sheath or paranodal seal involvement in motor fibers and, possibly, paranodal detachment in sensory fibers.SIGNIFICANCE: Excitability properties of affected nerves in MMN differ between motor and sensory nerve fibers.
AB - OBJECTIVE: To assess excitability differences between motor and sensory axons of affected nerves in patients with multifocal motor neuropathy (MMN).METHODS: We performed motor and sensory excitability tests in affected median nerves of 20 MMN patients and in 20 age-matched normal subjects. CMAPs were recorded from the thenar and SNAPs from the 3rd digit. Clinical tests included assessment of muscle strength, two-point discrimination and joint position.RESULTS: All MMN patients had weakness of the thenar muscle and normal sensory tests. Motor excitability testing in MMN showed an increased threshold for a 50% CMAP, increased rheobase, decreased stimulus-response slope, fanning-out of threshold electrotonus, decreased resting I/V slope, shortened refractory period, and more pronounced superexcitability. Sensory excitability testing in MMN revealed decreased accommodation half-time and S2-accommodation and less pronounced subexcitability. Mathematical modeling indicated increased Barrett-Barrett conductance for motor fibers and increase in internodal fast potassium conductance for sensory fibers.CONCLUSIONS: Excitability findings in MMN suggest myelin sheath or paranodal seal involvement in motor fibers and, possibly, paranodal detachment in sensory fibers.SIGNIFICANCE: Excitability properties of affected nerves in MMN differ between motor and sensory nerve fibers.
KW - Excitability
KW - Ion channels
KW - Motor axons
KW - Multifocal motor neuropathy
KW - Schwann cell
KW - Sensory axons
UR - http://www.scopus.com/inward/record.url?scp=85090884557&partnerID=8YFLogxK
U2 - 10.1016/j.clinph.2020.08.004
DO - 10.1016/j.clinph.2020.08.004
M3 - Article
C2 - 32947198
SN - 1388-2457
VL - 131
SP - 2641
EP - 2650
JO - Clinical Neurophysiology
JF - Clinical Neurophysiology
IS - 11
ER -