NEEDLE EMG OF THE TONGUE - MOTOR UNIT ACTION-POTENTIAL VERSUS PEAK RATIO ANALYSIS IN LIMB AND BULBAR ONSET AMYOTROPHIC-LATERAL-SCLEROSIS

Objectives-to find out if conventional and automatic needle EMG of the tongue can be helpful in the diagnosis and differentiation of limb an d bulbar onset amyotrophic lateral sclerosis. Methods-Motor unit actio n potential (MUAP) analysis and peak ratio interference pattern analys is were performed in the right genioglossus muscle of 30 healthy subje cts aged 30-81 years, 10 patients aged 49-73 years with limb onset amy otrophic lateral sclerosis, and eight patients aged 52-75 years with b ulbar onset amyotrophic lateral sclerosis. Electrical activity was sam pled via standard concentric needle electrodes with a commercially ava ilable EMG recorder. Results-Normal mean (2SD) MUAP duration was 6.6 ( 1.5) ms. Normal mean (2SD) MUAP amplitude was 224 (97.4) mu V. Normal mean (2SD) peak ratio (PR), turns/second (T/s), amplitude/turn (A/T), and time intervals (TI1, TI2, TI3) were 1.68 (0.56), 732 (303.9), 446 (180.3) mu V, 2.62 (0.34), 2.31 (0.14), and 1.01 (0.50) respectively. Mean MUAP duration and amplitude were significantly increased in limb onset (P = 0.0001 and P = 0.013) and bulbar onset amyotrophic lateral sclerosis (P = 0.0001 and P = 0.017). Peak ratio indices stayed unchan ged in limb onset amyotrophic lateral sclerosis but were significantly decreased (PR, T/s, AIT, TI1, and TI2) or increased (TI3) in bulbar o nset disease. The sensitivity of the MUAP analysis was 70% in limb and 75% in bulbar onset amyotrophic lateral sclerosis. The sensitivity of the peak ratio interference pattern analysis was 20% in limb and 100% in bulbar onset amyotrophic lateral sclerosis. Subclinical involvemen t of the tongue was found in 20% of the patients with limb onset amyot rophic lateral sclerosis and could be more accurately assessed with MU AP analysis than with automatic EMG. Conclusions-both conventional and automatic needle EMG of the tongue are valuable electrophysiological devices to assess the clinical and subclinical involvement of the tong ue in patients with limb and bulbar onset amyotrophic lateral sclerosi s.