Non-invasive measurement of the latency in somatosensory evoked potentials from tactile stimulation

The measurement of latency of the sensory potentials evoked by tactile stimuli can be done as a support for the diagnosis of diseases like diabetic peripheral neuropathy. The most used measurement method for recording such signals requires long needle electrodes to be inserted near the nerves under study as the signals coming from surface electrodes have a too low Signal-to-Noise Ratio (SNR). The paper shows how it is possible to overcome such limitation by means of a selective digital filtering that greatly improves the SNR allowing the latency measurement. A measurement instrument implementing such approach has been realized executing the tactile stimulation, the electrode signal amplification, digitization and filtering. The first validation phase has been carried out by measuring the latency on simulated as well as actual signals coming from healthy people and comparing them with reference signals coming from literature and from invasive measurements. The first results show a good agreement, particularly between the invasive and non-invasive methods.