ABSTRACT
UNLABELLED: Evoked potentials and disability in multiple sclerosis: a different perspective to a neglected method. OBJECTIVE: Because evoked potentials (EP) are reflections of the functional integrity of sensory-motor systems, they are expected to reflect the abnormality in patients with disabilities and handicaps and also be in correlation with scales. This assumption was tested. METHODS: Patients with multiple sclerosis (MS) and myelopathy (M) and normal controls were investigated by EP, Multiple Sclerosis Walking Scale-12, timed 25-foot walk test and extended disability status scale (EDSS). EP results were converted to ordinal values, and correlations of these values with scales were calculated. Sensitivity and specificity analysis of EP parameters was also performed. RESULTS: Total EP scores revealed high rates of abnormality in both groups, but MS revealed a different correlation pattern from M. The SEP+MEP summed score showed high sensitivity and specificity for MS and this was also correlated with the MS-related disability-ambulation scales including EDSS. The most specific parameter was the minimum M latency in the MEP study. CONCLUSIONS: Four extremity recordings of EP with the use of more parameters than usual and ordinal expression of results seem to be benefical in MS. Although this study was cross sectional in nature, results indicated that EP might be useful in clinical follow up.
Subject(s)
Electroencephalography/standards , Evoked Potentials, Motor/physiology , Evoked Potentials, Somatosensory/physiology , Multiple Sclerosis, Relapsing-Remitting/physiopathology , Spinal Cord Diseases/physiopathology , Adult , Aged , Aged, 80 and over , Electroencephalography/methods , Electromyography/methods , Electromyography/standards , Exercise Test , Female , Humans , Male , Middle Aged , Multiple Sclerosis, Relapsing-Remitting/diagnosis , Sensitivity and Specificity , Severity of Illness Index , Spinal Cord Diseases/diagnosis , Young AdultABSTRACT
Long-latency reflexes (LLRs) of hand muscles include a transcortical component. Cortical relay time estimated by the subtraction of motor and somatosensory evoked potentials from LLR reflects the physiology of the central neural pathway of LLR. It is believed that 1-Hz repetitive transcranial magnetic stimulation (rTMS) of the primary motor cortex can decrease cortical excitability for approximately 15 minutes at intracortical level. The aim of the study was to analyze LLR and cortical relay time before and after 1-Hz rTMS. Long-latency reflex and H reflex obtained from the thenar muscles by electrical stimulation of the median nerve of 16 healthy subjects. Additionally, motor evoked potentials and somatosensory evoked potentials were also recorded. Cortical relay time was calculated by the subtraction of motor evoked potential and somatosensory evoked potential latencies from LLR. These electrophysiologic recordings were performed before and after 15 minutes of 1-Hz rTMS over the motor area for the thenar muscles in the primary motor cortex. The amplitudes of LLR and motor evoked potential were significantly decreased after rTMS, but the H reflex of the thenar muscle and somatosensory evoked potentials were unchanged. The major finding of our study was a shortened duration of cortical relay time after rTMS. In conclusion, our findings suggest that the LLR of the thenar muscles has a transcortical pathway and cortical relay time that can give some information about the physiology of the intracortical pathway of LLR.
