P63-S Insidious neuromuscular deterioration in polio survivors demonstrated by CMAP scan analysis

Background This study aimed to explore the subtle motor unit(MU) changes in asymptomatic muscles of poliomyelitis survivors (PS) using CMAP Scan analysis. Material and method Nineteen PS cases and 21 controls were recruited. CMAP Scan recordings were obtained from asymptomatic thenar and hypothenar muscles. CMAP Scan parameters indicating nerve excitability [stimulus intensities producing 50%, 95% and 5% of the CMAP amplitude (SI%5, SI%50, SI%95), absolute range width (ARW) (SI%95-SI%5), relative width (RW) (SI95 − SI5)/SI5], all step parameters and D50 which reflect the MU motor unit loss and reinnervation were analyzed. The new motor unit number estimation (MUNE) method, MscanFit was also calculated. Results There were no significant differences in ages, maximum CMAP amplitudes and MScanFit MUNE between the groups. PS group median and ulnar D50 values (46.76 ± 10.98, 46.19 ± 12.42 respectively) were lower than control group (37.21 ± 17.37, 36.44 ± 11.99) ( p p p Conclusions CMAP Scan can show reduced axonal excitability and reveal insidious MU loss and reinnervation in presumably unaffected muscles of PS, regardless of the decrease in CMAP amplitudes or a significant reduction in MUNE values.