Utility of vibration thresholds in patients with brachial plexus nerve compression

The diagnosis of brachial plexus nerve compression is controversial due to the subjective nature of patient symptoms and the lack of objective, quanti fiable tests. It has been hypothesized that quantitative sensory evaluation of sensory threshold is the most sensitive method of evaluating nerve comp ression, particularly in the early stages. This study evaluated the sensiti vity and specificity of vibration thresholds for detection of brachial plex us nerve compression. A multiple-frequency vibrometer was used to evaluate 40 control subjects and 35 patients with brachial plexus nerve compression. Calculated sensitivity values were modest (0.49 at 63, 250, and 500 cps) w ith high specificity values (0.98 at 8 cps) for individual frequencies usin g a fifth percentile criterion. The low sensitivity values indicate that th is instrument is not adequate as a screening device.