Anterior Horn CellsSpinal Muscular Atrophies of ChildhoodMuscular Atrophy, SpinalNeuronal Apoptosis-Inhibitory ProteinSMN Complex ProteinsSpinal CordSurvival of Motor Neuron 1 ProteinSpinal Cord DiseasesMuscular AtrophyMotor NeuronsElectromyographyHornsPosterior Horn CellsMenisci, TibialArthrogryposisParalysisNeuromuscular DiseasesMotor Neuron DiseaseAmyotrophic Lateral SclerosisSpinal Nerve RootsNeural Conduction