Correlation between loss of motor unit and jitter abnormality in amyotrophic lateral sclerosis

55 Vm. SUMMARY: ALS is pathologically characterized by degeneration of muscle fibers, secondary to degeneration of motor neurons in the spinal cord. In this study, jitter, fiber density and motor unit number estimates were measured in ALS patients. It was hypothesized that if a meaningful relation existed between these electrophysiologic measurements, single fiber EMG, used more often in routine electrodiagnostic investigations, would be good predictor of the natural history of the disease. We found the jitter displayed a good correlation with manual muscle scores (p=0.02 r=-0.589), upper extremity function (p=0.009 r=0.649) and MUNE (p=0.024 r=-0.574). Fiber density was not significantly correlated with manual muscle scores, functional scoring and MUNE (p>0.05). Mean sMUP was significantly associated with manual muscle scores (p=0.012 r=-0.628) and upper extremity function (p=0.004 r=0.698), whereas MUNE showed a good relation with manual muscle scores (p=0.003 r=0.704), upper extremity function (p=0.012 r=-0.630) and CMAP amplitude (p=0.000 r=0.939). It was concluded that as mean jitter showed a good relation with MUNE, this measurement would be helpful in identifying more severely affected patients.