Background: Volatile anesthetics attenuate medium-frequency (250 to 500 Hz) pulse train transcranial electrical stimulation (TES) motor-evoked potentials (MEPs) better than propofol. High-frequency (1000 Hz) TES may restore hand MEP amplitude under volatile anesthesia, but its effect on leg MEPs critical for spine surgery monitoring is unknown.
Methods: The effects of sevoflurane and propofol and modulation of the stimulation frequencies on MEPs elicited by TES in the anterior tibial, abductor hallucis, and abductor pollicic brevis muscles were investigated in 31 patients undergoing spine surgery.