Relevance of Brain Stem and Visual Evoked Potentials in Diagnosis of Central Demyelination in Guillain Barre Syndrome

Aims: Guillain Barre Syndrome (GBS) is an auto-immune mediated demyelination polyradiculo-neuropathy. Clinical features include progressive symmetrical ascending muscle weakness of more than two limbs, areflexia with or without sensory, autonomic and brainstem abnormalities. The purpose of this study was to determine subclinical neurological changes of CNS with GBS & to establish the presence of central demyelination in GBS.

Study Design: A prospective study to find out early Central demyelination in clinically diagnosed patients of GBS.

Place and Duration of Study: Department of Physiology, Pt. B.D. Sharma Post-Graduate Institute of Medical Sciences, University of Health Sciences, Rohtak, Haryana, India, between January 2014 and June 2015.

Methodology: The patients were referred from the Department of Medicine to our Department for electro-diagnostic evaluation. The study group comprised of 40 subjects (20 clinically diagnosed GBS patients and 20 healthy individuals) aged between 6-65years. Brain stem and visual evoked potentials were done in both groups using RMS EMG EP Mark II machine. BAEP parameters included the latencies of waves I to IV, inter-peak latencies I-III, III_IV & I-V while VEP included latencies of P100 waves.

Results: Statistically significant increase in absolute peak and inter-peak latency in the GBS group as compared to the control group was noted. Prolongation of latency of P100 wave latency in both the right and left eyes was also recorded in the GBS group.

Conclusion: Results of evoked potentials reflect impairment of auditory and visual pathways probably due to focal demyelination in Schwann cell derived myelin sheaths that cover the extra-medullary portion of the auditory nerves and also due to demyelination of optic pathways. Prolonged central conduction time in BAEPS & VEPS suggest the subclinical auditory and optical involvement in GBS. Early detection of the sub-clinical abnormalities is also important as timely intervention reduces morbidity and mortality.