Insights from Magnetic Evoked Field Analysis in Patients with Wilson's Disease.

Aims: To study the latency, amplitude, and source localization of magnetic evoked field (MEF) responses to visual, auditory, and somatosensory stimuli in Wilson's disease (WD) using magnetoencephalography (MEG) and compare it with "healthy" controls, and correlate the observations with disease severity and brain MRI.

Methods: MEF of 28 patients with neurological WD (age: 22.82 ± 5.8 years; M:F = 12:16) and 21 matched controls (age: 25.0 ± 4.6 years; M:F = 10:11) were recorded using MEG. Source localization was performed using standard models on the components of M100, M20, and M100 for visual, somatosensory, and auditory evoked fields, respectively and its latency/amplitude was correlated with disease severity.

Results: There were significant differences in source location between control and WD during visual evoked field (VEF) and auditory evoked field (AEF) studies. Latencies of M20 (right-p = 0.02; left-p = 0.04) and M32 (right-p = 0.01) components of SSEF were significantly prolonged. The amplitude of M20 was significantly reduced in patients bilaterally (P = 0.001). There was a trend for the prolonged latency of M100 of VEF in patients (P = 0.09). Five patients had reduced right M145 compared to 8 controls. The left somatosensory evoked fields (SSEF) latency correlated with disease severity (P = 0.04). There was no significant correlation between major components of other MEF with disease severity or MRI score.

Conclusions: This study, first of its kind to use MEF analysis in a large cohort of patients with WD, detected subclinical but a variable degree of abnormalities, most consistently of SSEF. It provides valuable insights of functioning and localization of various pathways in a disease known to have protean clinical manifestations and widespread MRI changes.