Constant current sine wave transcutaneous nerve stimulation for the evaluation of peripheral neuropathy.

We have evaluated various forms of peripheral neuropathy with a new device which emits a constant sinusoid stimulus at varying frequencies to quantitate current perception thresholds (CPTs). In normal individuals, CPT measures increase with increasing stimulation frequency, are highest on the toe and lowest on the face. There is a significant effect of age and sex on threshold perception. In patients with neuropathy, there is a marked increase in thresholds on hands and feet, as well as a lesser but still significant increase of facial CPTs. Thresholds furthermore correlated with clinical severity in a group of patients with diabetic neuropathy. Facial thresholds were markedly elevated in the patients with moderate to severe neuropathy, suggesting that the device is sensitive to the systemic nature of peripheral neuropathy. The authors believe the device will be a useful tool in screening for sensory neurologic abnormalities.