What can we assess with EMG? Erik Stålberg Uppsala Sweden Muscle membrane function - spontaneous Muscle fibre characteristics; diameter MU organization number of fibers grouping N-M transmission Motor units total number activation; pattern, fullness Stålberg Parameters to quantify in Conc/Monopolar EMG spontaneous activity shape of individual MUPs jiggle recruitment (early, reduced) fullness at strong activation dynamic changes with time (fatigue) 1
Spontaneous activity in normal Visual scoring Spontaneous activity from the muscle insertional activity end-plate noise nerve spikes positive wave at end-plate zone FINDING fibrillation potentials, psw myotonic discharges CRD myokymic discharges myogenic extra discharges MEASURE AS #/ 10 recording sites or +, ++, +++, ++++ few moderate abundant or spontaneous or after provocation FINDING neuromyotonic discharges myokymic discharges muscle cramps fasciculations neurogenic extra discharges Visual scoring Spontaneous activity from the nerve MEASURE AS #/ 10 recording sites or +, ++, +++, ++++ few (per time unit) moderate abundant indicate spontaneous or after provocation Spontaneous activity in myopathy Fib, PSW? Myotonic Disch.? No CRD? No Muscular dystrophies Myositis, IBM Debrancher Glycogenosis Acid Maltase Deficiency Hyperkalemic per paralysis Myotonic conditions LGMD 1A Nemaline myopathy Myotubular myopathy Mitochondrial myopathy Carnitine Deficency Hypothyroid myopathy Rhabdomyolysis oxic - Chloroquine - Alcoholic -Statins - Colchicine Courtesy R.Liguori, modified 2
Spontaneous activity in myopathy Spontaneous activity in myopathy Muscular dystrophies Muscular dystrophies Myositis, IBM Myositis, IBM Debrancher Glycogenosis Debrancher Glycogenosis Fib, PSW? Acid Maltase Deficiency Hyperkalemic per paralysis Myotonic conditions Fib, PSW? Acid Maltase Deficiency Hyperkalemic per paralysis Myotonic conditions LGMD 1A LGMD 1A Myotonic Disch.? Nemaline myopathy Myotubular myopathy Myotonic Disch.? Nemaline myopathy Myotubular myopathy Mitochondrial myopathy Mitochondrial myopathy Carnitine Deficency Carnitine Deficency CRD? No Hypothyroid myopathy Rhabdomyolysis CRD? Hypothyroid myopathy Rhabdomyolysis oxic - Chloroquine oxic - Chloroquine - Alcoholic - Alcoholic - Statins -Statins - Colchicine - Colchicine Spontaneous activity in myopathy Spontaneous activity in myopathy Muscular dystrophies Muscular dystrophies Myositis, IBM Myositis, IBM Debrancher Glycogenosis Debrancher Glycogenosis Fib, PSW? Acid Maltase Deficiency Hyperkalemic per paralysis Myotonic conditions Fib, PSW? No Acid Maltase Deficiency Hyperkalemic per paralysis Myotonic conditions LGMD 1A LGMD 1A Myotonic Disch.? No Nemaline myopathy Myotubular myopathy Mitochondrial myopathy Myotonic Disch.? Nemaline myopathy Myotubular myopathy Mitochondrial myopathy Carnitine Deficency Carnitine Deficency CRD? Hypothyroid myopathy Rhabdomyolysis CRD? No Hypothyroid myopathy Rhabdomyolysis oxic - Chloroquine oxic - Chloroquine - Alcoholic - Alcoholic - Statins -Statins - Colchicine - Colchicine 3
Conc. EMG signals from 2-15 muscle fibers Central spike Slow wave components Stålberg Monopolar EMG Generation of a MUP Central spike Slow wave components Stålberg 4
diameter 50±5 µm 10 mm from end plates normal size close rec. Simulation studies effect of rec. pos. effect of fiber size diameter 50±5 µm diameter 50±5 µm 30 mm from end plates 10 mm from end plates normal size dist. rec. normal size close rec. Simulation studies effect of rec. pos. effect of fiber size 5
diameter 40±15 µm diameter 40±15 µm 10 mm from end plates 30 mm from end plates diam. variation close rec. diam. variation close rec. Parameters used in MUP analysis start at nmj opposite side of nmj phase duration end of prop at tendon repolarisation slowly prop SFAP Stålberg parameter significance measurement Amplitude # fibers/0.5mm peak-peak Area # fibers/2 mm within dur Duration # fibers in 2.5 mm slope criteria hickness # close fibre area/ampl Size index MU size normalized thickness Phases temp dispersion 0-cross + 1 urns change in dir Irregularity length/ampl Rise time closeness to fibre neg-pos peak Satellites extreme delay late spike Jiggle n-m transm shape stability Stålberg 6
Decomposition; techniques to decompose a mixed signal into its constituents his example: Multi MUP analysis Stålberg Multi-MUP analysis in different disorders A Normal Neuropathy B C Myopathy 500 uv 10 ms Stålberg 7
A m p L I t u d e Amplitude Measured peak-peak * note that jiggle will reduce mean amplitude (measured after averaging) Duration area 8
C O M P L E X I Y Area Phases, turns Positive and negative signal segment between duration cursors; mvmsec he jiggle Phases, turns Way to express complexity >4 phases = polyphasic > 5 turns = complex, serrated 9
he jiggle he jiggle he jiggle he jiggle 10
Jiggle in normal and abnormal MUPs Normal So, shall I use all these parameters?? Which one is best? ALS Let us look at the diagnostic power of a few parameters Stålberg Amplitude (ib.ant.) Duration polymyositis 0.87 polymyositis 0.88-2SD +2SD SD ALS ALS,13.46 SD Stålberg,Erdem unpublished Stålberg,Erdem unpublished 11
Area Reference values necessary to separate abnormal from normal polymyositis.36 his is a crucial point in quantitative EMG analysis ALS mean, SD (# of SDs = Z-score) median, percentiles outliers combine different data (multivariate analysis, index) 0,85 Stålberg,Erdem unpublished A few examples Combination of abnormally small and large MUPs (Hereditary distal myopathy) Combination of abnormally small and large MUPs (Hereditary distal myopathy) outlier outliers Lat vastus m Lat vastus m 12
Methods Interference pattern recruitment analysis visual inspection (ampl, fullness) spectral analysis broad band filter analysis turns/amplitude analysis envelope, NSS, activity Myopathy Normal Neuropathy Stålberg, Daube 2003 13
Frequency bands in EMG, schematic 20 neuropathy 15 10 5 LUCIA 0 15 0-50 1 200-300 4 5 1000 9 Hz 10 2 3 6 7 8 11 12 normal 10 5 0 15 1 2 3 4 5 6 7 8 9 10 11 12 0-50 200-300 1000 Hz myopathy 10 5 0 1 2 3 4 5 6 7 8 9 10 11 12 0-50 200-300 1000 Hz mbiceps brachii EMG power spectrum urns-ampl (A) analysis normal myopathy neuropathy Neuropathy Normal Myopathy A Fuglsang-Frederiksen 14
ib ant Comparison of electrophysiological parameters Parameters nm-j myopathy den/reinn axon loss CB central SFEMG n n n Conv MUP abn n n n Conv IP n myo neur Macro n n n n n IP MUP MUNE n n n n n MS n n n abn Myopathy ib ant 18446 Reasons for performing QEMG standardized way of measuring improved sensitivity results can be transferred from one time to the other - follow up from one physician to the other from on lab to the other reliable results also from less experienced EMGers good during training 15