Using advanced analysis of multifocal visual-evoked potentials to evaluate the risk of clinical progression in patients with radiologically isolated syndrome

This study aimed to assess the role of multifocal visual-evoked potentials (mfVEPs) as a guiding factor for clinical conversion of radiologically isolated syndrome (RIS). We longitudinally followed a cohort of 15 patients diagnosed with RIS. All subjects underwent thorough ophthalmological, neurological and imaging examinations. The mfVEP signals were analysed to obtain features in the time domain (SNRmin: amplitude, Latmax: monocular latency) and in the continuous wavelet transform (CWT) domain (bmax: instant in which the CWT function maximum appears, Nmax: number of CWT function maximums). The best features were used as inputs to a RUSBoost boosting-based sampling algorithm to improve the mfVEP diagnostic performance. Five of the 15 patients developed an objective clinical symptom consistent with an inflammatory demyelinating central nervous system syndrome during follow-up (mean time: 13.40 months). The (SNRmin) variable decreased significantly in the group that converted (2.74 ± 0.92 vs. 4.07 ± 0.95, p = 0.01). Similarly, the (bmax) feature increased significantly in RIS patients who converted (169.44 ± 24.81 vs. 139.03 ± 11.95 (ms), p = 0.02). The area under the curve analysis produced SNRmin and bmax values of 0.92 and 0.88, respectively. These results provide a set of new mfVEP features that can be potentially useful for predicting prognosis in RIS patients.

Occipital repetitive transcranial magnetic stimulation does not affect multifocal visual evoked potentials

Background To identify mechanisms of cortical plasticity of the visual cortex and to quantify their significance, sensitive parameters are warranted. In this context, multifocal visual evoked potentials (mfVEPs) can make a valuable contribution as they are not associated with cancellation artifacts and include also the peripheral visual field. Objective To investigate if occipital repetitive transcranial magnetic stimulation (rTMS) can induce mfVEP changes. Methods 18 healthy participants were included in a single-blind crossover-study receiving sessions of excitatory, occipital 10 Hz rTMS and sham stimulation. MfVEP was performed before and after each rTMS session and changes in amplitude and latency between both sessions were compared using generalized estimation equation models. Results There was no significant difference in amplitude or latency between verum and sham group. Conclusion We conclude that occipital 10 Hz rTMS has no effect on mfVEP measures, which is in line with previous studies using full field VEP.

Cerebral Functional Magnetic Resonance Imaging and Multifocal Visual Evoked Potentials in a Patient with Unexplained Impairment of Visual Function: A Case Report

We present a case of a young female with a slowly progressing visual impairment who was examined with multifocal visual evoked potentials and functional magnetic resonance imaging (fMRI) for underlying neuronal abnormality. The fMRI examination consisted of presenting black-and-white checkerboard stimuli, and her activation patterns were compared to the patterns from 4 normal-sighted subjects. The results showed clear differences in neuronal activation between the patient and the controls in the occipital and parietal lobes. Although we have shown neuronal correlates in a case of unexplained visual loss, it is still an open question as to whether this has an organic or functional cause, which should be the subject for future research.