ABSTRACT
Magnetic stimulation was used to measure motor conduction time (MCT) between head and neck, and head and lumbar region, as well as amplitude of the motor evoked potential (MEP) in normal subjects and patients with multiple sclerosis (MS). Patients with definite MS had significantly longer MCTs and smaller amplitude MEPs than normal subjects when recording from arm and leg muscles. In a comparison with visual evoked potential (VEP) recordings, head to neck MCTs were abnormal less often than VEPs, and VEPs detected more silent lesions. Recording from leg as well as arm muscles significantly increased the yield of abnormal MCT measurements. The detection of silent lesions in the patients with definite MS was improved, but there was no improvement in the non-definite cases. Amplitude measurements provided very little extra diagnostic information over MCT measurements alone and did not improve the detection of silent lesions. Interside MCT differences yielded extra abnormalities when recording from the arms but not the legs. Interside MCT abnormalities increased the detection of silent lesions in both the definite and non-definite categories. It was concluded that the majority of useful diagnostic information in patients with MS should be obtainable from bilateral MCT (head to neck) measurements, together with estimation of interside MCT differences. However, VEP recording is a better diagnostic test for MS than MEP recording as more silent lesions are detected. This may be because MCT abnormalities tend to reflect the degree of pyramidal disability.
Subject(s)
Evoked Potentials , Magnetics , Multiple Sclerosis/diagnosis , Neural Conduction , Adult , Arm/innervation , Back/innervation , Evaluation Studies as Topic , Evoked Potentials, Visual , Female , Head/innervation , Humans , Leg/innervation , Male , Motor Neurons/physiology , Multiple Sclerosis/physiopathologyABSTRACT
Magnetic stimulation was used to measure motor conduction time (MCT) between head and neck in a prospective longitudinal study of patients with multiple sclerosis (MS) and normal subjects. MCT measurements showed a high degree of reproducibility in normal subjects and patients with stable MS. In patients with definite MS, there was significant positive correlation between MCT and motor disability. In patients treated with steroids for relapse of MS, there was significant shortening of MCT following treatment in those who clinically improved, but not in those who were clinically unchanged. In a smaller group of patients followed for 3 months, MCT changes tended to mirror the clinical pattern. Magnetic stimulation should prove a useful tool for the quantification of motor disability, and monitoring the response to new treatments in MS.
Subject(s)
Magnetics , Motor Neurons/physiology , Multiple Sclerosis/physiopathology , Neural Conduction , Adrenal Cortex Hormones/therapeutic use , Adult , Aged , Arm/innervation , Humans , Middle Aged , Multiple Sclerosis/drug therapy , Neck/innervation , Prospective Studies , Reproducibility of ResultsABSTRACT
The new technique of magnetic stimulation was used to measure amplitude of the motor evoked potential (MEP) recorded from abductor digiti minimi whilst stimulating at the head, and motor conduction time (MCT) between head and neck. Bilateral studies were made in 12 normal subjects and 56 patients with Parkinson's disease. The amplitudes of the MEPs were significantly larger (P less than 0.05) in the patients (mean 1.6 mV, SD 1.4) compared with the normal subjects (mean 0.9 mV, SE 0.6). MCTs were significantly shorter (P less than 0.001) in patients (mean 8.1 ms, SD 1.3) compared with the normal subjects (mean 9.4 ms, SD 1.2). Although the pathophysiological basis of these changes has not been determined, they provide objective measurements which may be clinically valuable in monitoring therapy.