Motor unit number estimation

Due to the anatomic location of motor neurons, it is has not been possible to directly quantify motor neuron loss in anterior horn cell disease. Motor neurons are located in the anterior spinal cord, one of the areas within the nervous system that are not amenable to biopsy and histological analysis in living patients. The spinal cord has a high density of eloquent fiber tracts. Biopsy-induced injury to these tracts would result in significant weakness, paraesthesiae and/or sphincter dysfunction. As a result, estimating the degree of actual motor neuron loss has remained elusive for motor neuron diseases such as amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA). Motor unit number estimation (MUNE) provides a reliable estimate of the number of functional motor units present in such diseases.