Multimodal neurophysiological evaluation of primary progressive multiple sclerosis - An increasingly valid biomarker, with limits

Background: The promising utility of multi-modality evoked potential batteries to objectively measure multi-tract dysfunction has been evaluated by several groups using different methods.

Objective: To independently evaluate the use of multi-modality evoked potential batteries as surrogate biomarkers for both physical and cognitive status in a cohort of Primary Progressive Multiple Sclerosis patients and identify the most potentially useful scoring method of those described.

Methods: 28 Patients with Primary Progressive Multiple Sclerosis underwent clinical evaluation with Kurtzke's Modified EDSS and the Multiple Sclerosis Functional Composite (MSFC). 19 Participants also underwent the Minimal Assessment of Cognitive Function in Multiple Sclerosis. Visual, Brainstem Auditory, Somatosensory and Motor Evoked Potentials were recorded on all. Results were graded by variants of the Global Evoked Potential Score, Multiple Evoked Potential Score and Summation of Z transformed Evoked Potential Latencies for correlation against the clinical scores.

Conclusions: Multi-modal evoked potential batteries generally show moderate and useful correlation with clinical status as measured by the regulatory standard of EDSS (r = .65 vs. mEPS p < .005) and MSFC (r = .39 vs. mEPS p < .05). The graded qualitative mEPS scoring system displayed the strongest relationship although the influence of scoring system applied appeared reassuringly minimal. Non-association with cognitive impairment is an important limitation however.