Cortical somatosensory magnetic responses in multiple sclerosis

Area of Science:

• Neuroscience
• Biophysics
• Clinical Neurology

Background:

• Multiple sclerosis (MS) is a demyelinating disease affecting the central nervous system.
• Somatosensory evoked magnetic fields (SEFs) provide a non-invasive method to assess the integrity of the somatosensory pathways.
• Understanding SEF alterations in MS can aid in diagnosing and monitoring disease progression.

Purpose of the Study:

• To investigate alterations in somatosensory evoked magnetic fields (SEFs) in patients with multiple sclerosis (MS).
• To correlate SEF abnormalities with lesion location identified by magnetic resonance imaging (MRI).
• To explore the diagnostic potential of early and middle-latency SEFs in MS.

Main Methods:

• SEFs were recorded using a 24-channel SQUID gradiometer in 10 MS patients and 8 healthy controls.
• Contralateral median and ulnar nerve stimulation was employed.
• Magnetic resonance imaging (MRI) was used to identify and localize lesions in MS patients.

Main Results:

• Seven out of ten MS patients exhibited abnormally large-amplitude SEF deflections at 60-80 milliseconds (ms).
• Five of these patients had multiple lesions around the lateral ventricles.
• Two patients with plaques in the ventricles and medulla showed enlarged 30 ms responses.
• Equivalent sources for early (20 ms) and middle-latency (30-80 ms) responses were localized to the primary hand sensorimotor cortex in both groups.

Conclusions:

• Early and middle-latency SEFs reflect parallel processing of somatosensory input.
• Abnormalities in middle-latency SEFs are associated with lesion load and location in MS.
• Recording middle-latency evoked responses, magnetic or electric, may enhance the assessment of somatosensory function in multiple sclerosis.