Neurophysiological studies of the neuromuscular junction

[Guest guest]

Rev Neurol. 2005 Aug 1-15;41(3):163-76.

Neurophysiological studies of the neuromuscular junction.

-Hidalgo M.

Hospital Clinico San , 28040 Madrid, Espana.

INTRODUCTION. The role played by neurophysiological studies (NPS) in

the diagnosis of diseases affecting neuromuscular transmission (NMT)

is based on the study of the failure of muscle fibres to achieve a

sufficient degree of depolarisation for the junction potential to

reach the appropriate threshold and attain a muscular action

potential. This totally or partially blocked impulse will give rise

to different types of responses in neurophysiological tests.

AIMS. To analyse the different NPS as diagnostic methods in diseases

that affect NMT.

DEVELOPMENT. The article offers a review of the concept of the safety

margin at the neuromuscular junction and a description of the most

common neurophysiological techniques currently in use -repetitive

stimulation, as well as conventional or single fibre electromyography

(EMG) with voluntary activation or axonal electrical activation-. The

most frequent findings in diseases affecting NMT are also discussed.

CONCLUSIONS. NPS will be useful to confirm or reject the clinical

diagnosis, to exclude other concomitant neuromuscular diseases, to

establish whether the process is pre- or post-synaptic, to monitor

the clinical course of the disease (when it is both natural or in

response to the medical or surgical treatment) and also to enable the

physician to determine the status of NMT in cases of clinical

remission, as well as to detect subclinical disorders. Single fibre

EMG studies are the most sensitive method of neurophysiological

diagnosis when dealing with these diseases.