Modulation of Somatosensory Evoked Potentials Via Focused Ultrasound Median Nerve Stimulation

Focused ultrasound (FUS) has been shown to modulate peripheral nerve activity, including decreasing perceived pain, with the acoustic radiation force proposed as the mechanism. Pain is subjective, however, and difficult to quantify. Instead, somatosensory evoked potentials (SSEP) from electrical stimulation can be used to quantify sensory signaling from the periphery to the brain and spinal cord. This study investigated the effect and mechanism of FUS median nerve neuromodulation by evaluating nerve displacement, cavitation, and changes in electrically-induced SSEPs. Median nerve FUS sonication at both 1.6 MPa and 2.5 MPa decreased SSEP amplitudes as measured by electroencephalography (EEG). Greater sonication pressure induced greater SSEP amplitude reductions and these reductions corresponded to the magnitude of cumulative median nerve displacement. SSEP reductions were not found with off-target sonication and no in vivo cavitation was found in any subject. Future work will apply this FUS median nerve sonication to modulate pain associated with carpal tunnel syndrome.