Long and short of nerve conduction measures: reproducibility for sequential assessments

With steady improvement and standardisation of methods, nerve conduction studies have become a reliable means of testing peripheral nerve function. They supplement clinical observation by precisely localising the lesion and characterising the conduction abnormalities. Delineating the extent and distribution of the neural lesion by this means also helps to quantify the degree of involvement. Optimal results can be expected only with proper choice of techniques, which in turn depends on the type of lesions under consideration. Thus, the studies must be conducted as an extension of the clinical examination, rather than a laboratory test. To document sequential changes for clinical follow up in general and for drug trials in particular, conduction studies must yield high sensitivity and reproducibility. A question often posed, but rarely tested in regard to these criteria relates to the length of the nerve segment under study. Other factors being equal, should shorter or longer segments be studied for better results?