1997•Muscle & NerveRequires access
Sural/radial amplitude ratio in the diagnosis of mild axonal polyneuropathy
Seward B. Rutkove, Milind J. Kothari, Elizabeth M. Raynor, Michele L. Levy, Ricardo Fadić, Rachel Nardin
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Abstract
As proximal nerves are relatively spared in length-dependent, axonal polyneuropathy, we theorized that a sural/radial amplitude ratio (SRAR) might be a sensitive indicator of mild polyneuropathy. In this study, sural amplitudes and SRARs in patients with signs of mild axonal polyneuropathy were compared to those of normal, age-matched control subjects. Sural and radial sensory responses were measured in a standard fashion in all subjects. Thirty polyneuropathy patients had an average SRAR of 0.29 as compared to 0.71 for the 30 normal subjects. An SRAR of less than 0.40 was a strong predictor of axonal polyneuropathy, with 90% sensitivity and 90% specificity, as compared to an absolute sural amplitude of less than 6.0 μV, which had sensitivity of only 66%. Additionally, unlike the sural amplitude, the ratio did not vary significantly with age. We conclude that the SRAR is a sensitive, specific, age-independent electrodiagnostic test for mild axonal polyneuropathy. © 1997 John Wiley & Sons, Inc. Muscle Nerve 20: 1236–1241, 1997