[Subclinical lesions of peripheral nervous system in multiple sclerosis patients]

In the last years the presence of peripheral nervous system (PNS) lesions has been noted in patients with multiple sclerosis (MS). The frequency and degree of PNS damage reported by many authors differ among publications, so does the type of PNS lesions. The aim of our study was to perform an electrophysiological evaluation of the peripheral nervous system in patients with a definite diagnosis of multiple sclerosis and without any clinical signs of peripheral neuropathy.

110 patients were included in the study, comprising 70 people with a definite diagnosis of multiple sclerosis and 40 people without any symptoms of organic nervous system lesion serving as a control group. During neurologic examination of MS patients the degree of disability measured by EDSS scale, the duration of the disease as well as number of relapses were assessed. A "disease progression factor" was calculated by dividing a number of relapses by disease duration in years. Patients with common etiologies for peripheral neuropathy such as diabetes, renal insufficiency, thyroid gland dysfunction, proliferative disorders etc. were excluded from the study. Orthodromic motor conduction and late responses (F wave) in median, ulnar, peroneal and tibial nerves as well as sensory conduction in median, ulnar (orthodromic) and sural (antidromic) nerves were evaluated.

There was electrophysiological evidence of peripheral nervous system lesions in at least one nerve in 52 (74.2%) MS patients. In 30 patients (42.8%) more than one peripheral nerve was lesioned. There were more significant differences noted during the examination of sensory nerves. Sensory amplitudes in all of the sensory nerves examined were significantly lower than in control group. Furthermore we observed slow sensory conduction velocities and prolonged sensory latencies in ulnar and sural nerves. There were significant differences between the two groups of patients concerning motor conduction too: prolonged distal latency in tibial and sural nerves, prolonged F wave latency in median, peroneal and tibial nerves, low motor amplitude in ulnar and peroneal nerves, low motor conduction velocity in ulnar nerve -- all noted in MS patients. We found no correlation between conduction parameters and the patients' age, disease duration, number of relapses and disease progression degree.

We found out that subclinical peripheral nervous system abnormalities are very frequent in MS patients. We noted both sensory and motor nerve lesions of a demyelinating-axonal character. Sensory abnormalities were more pronounced than motor ones. There was no correlation between the degree of PNS lesions and the patients' age and/or progression of multiple sclerosis.