DQEMG 20% data collection time was less (8.2 ± 1.9 vs. 13.7 ± 2.8 min.). Five to ten minutes was needed for off- line analysis only for DQEMG. Conclusion: DQEMG MUNE gives similar results to statistical MUNE more quickly and with less discomfort, but with greater variation among individuals. DQEMG offers a satisfactory alternative to statistical MUNE, but requires different normal values. doi:10.1016/j.clinph.2006.06.090 FC27.4 The electrophysiological muscle scan J. Blok , A. Ruitenberg, G. Visser Erasmus MC, Department of Clinical Neurophysiology, The Netherlands Background: Recording of compound muscle action potentials (CMAPs) in response to repetitive transcutane- ous stimulation of the motor nerve results in a so-called scan if stimulus intensity (SI) is gradually increased from subthreshold to supramaximal values. This electrophysio- logical muscle scan is used in a simple form in the statistical method of motor unit number estimation to derive sample ranges. By decreasing the SI step size by a factor of 10, the scan becomes a tool that shows much more detail. In this new form, it may be useful for other purposes as well. Objectives: To assess the information content and potential clinical value of the electrophysiological muscle scan. Methods: A scan of the m. abductor pollicis brevis was performed using 300 graded stimuli in 10 healthy subjects and 25 patients with various, mainly neurogenic, disorders. Response sizes were plotted versus SI, and the resulting scans were evaluated visually. Subsequently, this visual assessment was used to guide derivation of quantitative measures of the scan’s most important characteristics. Results: The scan contains clinically relevant informa- tion regarding denervating processes and axonal excitabil- ity. This information can be obtained visually and quantitatively from: (a) Steps, representing large, possibly reinnervated motor units (MUs); (b) Plateaus, resulting from large differences in stimulus threshold of groups of MUs; (c) CMAP variability, representing the number of simul- taneously probabilistically active MUs (alternation) and/or unstable MU potentials; and (d) SI values, reflecting overall axonal excitability at the stimulus site and excitability of the largest MUs individually. Conclusions: The electrophysiological muscle scan is an easy-to-use tool that can be applied qualitatively, for a quick overview of muscle characteristics, and quantitatively. Results of this pilot study merit further exploration and exploitation of the scan in electrodiag- nostic medicine. doi:10.1016/j.clinph.2006.06.091 FC28.1 MEMFIT: A computer program to aid interpreta- tion of multiple excitability measurements on human motor axons H. Bostock University College London, Institute of Neurology, UK Background: The measurement of multiple nerve excit- ability properties by automated threshold tracking has become a new tool to study peripheral neuropathies. The excitability measures, including strength–duration relationship, recovery cycle, and threshold electrotonus, contain information about membrane potential, ion channels and passive membrane properties. However, because of the electrical complexity of myelinated axons, interpretation of abnormal recordings has been uncertain. Aim: To provide a simple, objective means of interpret- ing abnormal nerve excitability recordings by matching them with a computer model. Method: A computer program was written in Visual Basic, based on a previously described 2-component (node + internode) model of human motor nerve excitabil- ity. This program allows: (1) tailoring the model to match recordings from a control group, (2) testing up to 30 parameters, to find which changes in 1, 2 or 3 parameters best account for the difference between the control and patient groups. The program was validated (a) on model data and (b) on recordings from experimentally altered normal nerves and from patients with well characterized neuropathies. Results: (a) All arbitrary changes in single model param- eters, and most changes in 2-parameters were correctly identified. (b) Membrane depolarization was identified as the most likely single change in normal nerves depolarized by DC current, Na + channel block as the most likely change in patients with puffer fish (TTX) poisoning, and an increase in nodal capacitance and fast K + conductance as the most likely change in 2-parameters in patients with CMT1A. Conclusion: zMultiple excitability data contains suffi- cient information for most changes in one or two model parameters to be identified correctly. For abnormal nerves, MEMFIT provides an objective interpretation of the likely underlying changes in membrane parame- ters which is more reliable than can currently be obtained by any other means. doi:10.1016/j.clinph.2006.06.092 Oral Communications / Clinical Neurophysiology 117 (2006) S49–S111 S85