Motor unit number estimation in human neurological diseases and animal models

Motor unit number estimation (MUNE) was introduced in 1971 as a way of prov iding an objective and meaningful estimate of axon loss in diseases affecti ng the motor system. Over the last 30 years, different methods of MUNE have been proposed, with each having specific strengths and limitations. The go al of this paper is to review the available methods, and to present data ge nerated using MUNE in a variety of disease entities. The incremental, multi ple point stimulation, spike-triggered averaging, F-wave, and statistical m ethods of MUNE are reviewed, along with data obtained using these methods i n patients with neuropathy, motor neuron disorders, and muscle disease. All methods reviewed have theoretical concerns associated with them. However, with the exception of the spike-triggered averaging method, all give result s in normal subjects that are quite similar. MUNE has been of great value i n assessing progression of motor neuron disease, and has also shown promise in the assessment of generalized neuropathy. Despite the lack of a perfect method for performing MUNE, it has great clinical value in the assessment of progressive motor axon loss. Further refinements in the method will like ly increase its utility in the future. (C) 2001 Elsevier Science Ireland Lt d. All rights reserved.