BACKGROUND:Amyotrophiclateralsclerosis(ALS)isthemostcommonofallthemotorneurondiseasesandtheabsenceofabiologicmarkerhasmadebothdiagnosisandtrackingevolutionofthediseasedifficult.Electrodiagnostictestsplayafundamentalroleinquantifyingpathologicalchangesinthemotorunitpool.OBJECTIVE:Weassesseddistal-proximalMotorUnit(MU)lossandchangesusingthemethodofmotorunitnumberestimation(MUNE).DESIGN,TIMEANDSETTING:Acase-controlstudywasperformedattheDepartmentofNeuroscience,PisaUniversityMedicalSchool,ItalyfromDecember1999toNovember2009.PARTICIPANTS:Atotalof50ALSpatientswererecruited,30males:meanage(59.6±13.3)years20females:meanage(63.9±11.7)years;range(30-82)years;allpatientshadprobableordefiniteALS.Thirtyhealthyvolunteerswererecruitedfromdepartmentstaffs,including20malesand10females;meanage(57.7±13.8)yearsservedascontrols.METHODS:MUNEwasperformedforboththebicepsbrachiiandabductordigitiminimimusclesothesameside.Thetechniqueusedrelayedsubstantiallyonmanualincrementalstimulationofthemotornerve,knownastheMcComastechnique(50mssweepduration,againof2mV/pforMwave,0.5mV/pforeachstep;filters10-20kHz).MAINOUTCOMEMEASURES:MUNEresultsweremeasured.RESULTS:FunctioningMUnumbers,measuredbyMUNE,decreasedinthebicepsbrachiiandabductordigitiminimimusclesovertheentireone-yearfollow-upperiod(oneassessmenteverythreemonths)comparedwithbaselinedetermination,therateofMUdecreasewassimilarinbothmuscles,butsteeperdistally.CONCLUSION:MUNEisafeasiblemethodforALSpatientsbothproximallyanddistallytotrackchangesovertimeinmuscleMUsduringthedisease'sevolution.
