Mirror movements in amyotrophic lateral sclerosis

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Abstract

Background

Mirror movements (MMs) are involuntary movements that suggest a upper motor neuron involvement.

Objectives

The aim of this study was to assess the MMs phenomena as an early sign of upper motor neuron involvement in amyotrophic lateral sclerosis (ALS).

Patients and methods

Fifty patients with ALS were subjected to full clinical neurological examination and identification of the MMs phenomena in both upper limbs (ULs) and lower limbs (LLs), if present. Detection of MM was performed using a surface electromyography (EMG) study from the abductor digitiminimi and tibialis anterior muscles and transcranial magnetic stimulation and simultaneous recording of the EMG activity and motor evoked potentials (MEPs) from the ipsilateral and contralateral sides.

Results

MMs were detected by analyzing ipsilateral MEP and the EMG of the patients examined. MMs detected by EMG of the examined muscles correlated well with the increased muscle tone, exaggerated reflexes, and central motor conduction time in LLs. The specificity of the MM and the positive predictive value were higher compared with the sensitivity and the negative predictive value. Subclinically, MMs were detected by analysis of ipsilateral MEP of LLs (27%), ULs (45%), and by the EMG of the ULs (45%) and the LLs (45%).

Conclusion and recommendations

MMs are rarely detected clinically in ALS, but they can be detected using electrophysiological procedures such as the MEP and the EMG. Detection of MM is a good specific test with high positive predictive value in diagnosing the ALS.

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