A useful electrophysiological test for diagnosis of minimal conduction block

Objective: To evaluate the usefulness, sensitivity and specificity of a new neurophysiological test for partial conduction block. Methods. In 17 patients (17 nerves) with clinical pictures strongly suggest ing the presence of motor conduction block and 20 healthy subjects (40 nerv es), motor nerve conduction studies were performed with the conventional su rface technique and with a new technique developed by us: the single fiber EMG (SFEMG) conduction block test. Moreover, we also evaluated patients wit h other neurological diseases. The recent American Association of Electrodi agnostic Medicine (AAEM) consensus criteria for partial conduction block we re used for the standard conduction block tests. Results: According to AAEM consensus criteria, 5/17 cases presented 'defini te' partial conduction block and 6 presented 'probable' partial conduction block. In contrast, 16/17 cases (94%) presented evidence of conduction bloc k at the SFEMG conduction block test. The 5/6 cases that did nor fulfill in the AAEM criteria and that presented abnormal findings at SFEMG nerve cond uction test could be considered affected by minimal conduction block. The s ensitivity of this new test was greater than conventional test. The specifi city was 100% (no abnormal findings in healthy subjects or patients with di seases other than neuropathy). Conclusions: The SFEMG conduction block test is a sensitive, complementary, technique for diagnosis of minimal conduction block in patients with norma l findings in standard nerve conduction studies. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.