Development and Validation of a New Hardware for a Somatosensorial Electrical Stimulator Based on Howland Current-Source Topology

Several neuropathies of the peripheral nervous system (PNS) cause sensory dysfunction, leading to information distortion or even sensory loss. For instance, Diabetes nerve-damaging process leads to progressive loss of sensation, which indicates that an early intervention could reduce its effects. Among available exams, electrical stimulation can provide quantitative metrics as current perception threshold (CPT) and reaction time (RT), which would serve as a screening tool for assessing the disease's evolution and differentiate the affected nerve fibers. We aim at developing a new multichannel hardware for the electrical stimulation system EELS, which would allow it to overcome limitations of the Neurometer and NeuroStim systems. We employ the Howland current-source topology combined with a bootstrapping power supply scheme to simplify the circuit design, reducing power stages and the number of required power rails. The new hardware presents high output linearity and stable load regulation when tested at frequencies (ranging from 1Hz to 3 kHz). It can generate current stimulus of up to 8.63 mA with 4.51 mu A resolution, showing total harmonic distortion (THD) inferior to 1%. When compared with NeuroStim and Neurometer, EELS presented similar or superior characteristics in term of stimulus generation (amplitude, frequency, bandwidth, linearity, and THD). Moreover, it presents two stimulation channels for the support of new exam protocols as, e.g., a two-point discrimination test. Therefore, EELS can be used for all the exams performed by its competitors (Neurometer and NeuroStim), adding new features to perform different exams.