Steady-state analysis of somatosensory evoked potentials

• Published in: Electroencephalography and clinical neurophysiology Vol. 100; no. 5; pp. 453 - 461
• Main Authors: Noss, Roger S., Boles, Colby D., Yingling, Charles D.
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 01.09.1996; Amsterdam Elsevier
• Subjects: Adult; Amplitude modulation; Biological and medical sciences; Cerebrospinal fluid. Spinal cord. Spinal roots. Spinal nerves; Electric Stimulation; Evoked Potentials, Somatosensory - physiology; Fourier analysis; Humans; Intraoperative monitoring; Male; Median Nerve - physiology; Median nerve stimulation; Medical sciences; Middle Aged; Neurosurgery; Somatosensory evoked potentials; Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases; Amplitude modulation; Fourier analysis; Intraoperative monitoring; Median nerve stimulation; Somatosensory evoked potentials; Peripheral nervous system; Human; Spinal cord; Methodology; Electrical stimulus; Central nervous system; Electrophysiology; Frequency domain method; Wrist; Analysis method; Surgery; Median nerve; Somatosensory evoked potential; Monitoring
• ISSN: 0168-5597; 0013-4694
• DOI: 10.1016/0168-5597(96)96011-6

We report the development of a new method for frequency domain analysis of steady-state somatosensory evoked potentials (SEPs) to amplitude-modulated electrical stimulation, which can be recorded in significantly less time than traditional SEPs. Resampling techniques were used to compare the steady-state SEP to traditional SEP recordings, which are based on signal averaging in the time domain of cortical responses to repetitive transient stimulation and take 1–2 min or more to obtain a satisfactory signal/noise ratio. Median nerves of 3 subjects were stimulated continuously with electrical alternating current at several modulation frequencies from 7 to 41 Hz. Amplitude modulation was used to concentrate the power in higher frequencies, away from the modulation frequency, to reduce the amount of stimulus artifact recorded. Data were tested for signal detectability in the frequency domain using the T circ 2 statistic. A reliable steady-state response can be recorded from scalp electrodes overlying somatosensory cortex in only a few seconds. In contrast, no signal was statistically discriminable from noise in the transient SEP from as much as 20 s of data. This dramatic time savings accompanying steady-state somatosensory stimulation may prove useful for monitoring in the operating room or intensive care unit.