Relapses in multiple sclerosis: effects of high-dose steroids on cortical excitability.
OBJECTIVE
High-dose steroid administration is the usual treatment of multiple sclerosis (MS) relapse, but it remains to determine whether this treatment may act by changing the excitability of cortical circuitry.


METHODS
The functional cortical effects of high-dose steroids in 21 MS patients before and after 3 days of intravenous administration of methylprednisolone (1 g/day) for the treatment of MS relapse were studied. Investigations included various clinical scales [Kurtzke Functional System Scale (KFSS), Expanded Disability Status Scale and Fatigue Severity Scale, 10-m walk] and transcranial magnetic stimulation (TMS) tests of cortical excitability [resting motor threshold, recruitment curve of motor evoked potentials, short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) at various interstimuli intervals (ISIs), cortical silent period and interhemispheric inhibition].


RESULTS
Following steroid administration, clinical improvement was significant for the KFSS pyramidal (motor) and total scores, whilst TMS showed a reduction of SICI (mean and maximum values) and an increase of ICF at 10 ms ISI.


CONCLUSIONS
Very rapid functional changes in the excitability of cortical circuits involved in motor control can be induced by steroids, before any process of remyelination or axonal regeneration has time to occur. The net effect of steroids on the balance between intracortical GABAergic inhibition and glutamatergic facilitation was in favour of weaker inhibition or stronger facilitation, which could lead to improving the motor performance in MS patients.
EA 4391, Faculté de Médecine de Créteil, Université Paris Est Créteil, Créteil, France; Service de Physiologie, Explorations Fonctionnelles, Hôpital Henri-Mondor, AP-HP, Créteil, France.
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SS
Ayache
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A
Créange
W H
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Farhat
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HG
Zouari
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Mylius
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Ahdab
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Abdellaoui
J-P
JP
Lefaucheur
D061605:Administration, Intravenous; D000328:Adult; D000368:Aged; D004185:Disability Evaluation; D004558:Electric Stimulation; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000187:drug effects* / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000187:drug effects / Q000502:physiology; D005938:Glucocorticoids / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D008775:Methylprednisolone / Q000627:therapeutic use*; D008875:Middle Aged; D009044:Motor Cortex / Q000187:drug effects* / Q000503:physiopathology; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000188:drug therapy* / Q000473:pathology*; D009433:Neural Inhibition; D011712:Pyramidal Tracts / Q000187:drug effects / Q000503:physiopathology; D011930:Reaction Time; D055815:Young Adult
D005938:Glucocorticoids; D008775:Methylprednisolone
cortical excitability; intracortical facilitation; multiple sclerosis; short-interval intracortical inhibition; steroids