Reference data for commonly used sensory and motor nerve conduction studies.

INTRODUCTION: The goal of this study was to generate reference data for a wide range of sensory and motor nerve conduction studies (NCSs) that are commonly used in routine electrodiagnostic practice.
METHODS: NCS data were collected from control subjects with a normal neurological examination and no known risk factors for or symptoms to suggest disease of the peripheral nervous system. Thirteen sensory and motor nerves were studied in the upper and lower limbs using standard recording techniques. Quantile regression was used to obtain estimates of the lower (e.g., 5th) percentiles for sensory and motor amplitudes and conduction velocities, as well as estimates of the upper (e.g., 95th) percentiles for distal motor latency and F-wave latencies.
RESULTS: Reference data for sensory and motor amplitudes required adjustment for age; F-wave latencies required adjustment for gender. Covariate adjustments were not required for other reference data. Data from N = 100 and N = 190 subjects permitted estimation of as low as the 4th and 2nd percentile, respectively, but further increases to N = 296 did not permit estimation of a more extreme percentile. DISCUSSION: Efforts to develop reference data require careful selection of study subjects; sufficient sample size; adjustment for relevant covariates; and appropriate statistical methods for analysis. Reference data that cannot be estimated reliably due to absent potentials or data variability must be interpreted with caution. We present data for a range of clinically applicable reference percentiles, but judgment regarding which is most appropriate for diagnostic purpose awaits empiric evaluation in a disease population.