CHAPTER 72 Somatosensory-Evoked Potentials and Spinal Surgery
5 At what points along the neurosensory pathway are somatosensory-evoked potentials most commonly recorded?
6 Describe the characteristics of the somatosensory-evoked potential waveform
The SSEP is plotted as a waveform of voltage vs. time. It is characterized by:


A waveform is identified by the letter describing its deflection above or below the baseline followed by a number indicating its latency (e.g., N20) (Figure 72-1).
7 Name several characteristic peaks important for the evaluation of somatosensory-evoked potentials
See Tables 72-1 and 72-2.
TABLE 72-1 Characteristic Peaks for Evaluation of Median Nerve Stimulation
Peak | Generator |
---|---|
N9 | Brachial plexus (Erb’s point) |
N11 | Dorsal root entry zone (cervical spine) |
N13, 14 | Posterior column (nucleus cuneatus) |
P14 | Medial lemniscus |
N20 | Somatosensory cortex |
TABLE 72-2 Characteristic Peaks for Evaluation of Posterior Tibial Nerve Stimulation
Peak | Generator |
---|---|
N20 | Dorsal root entry zone (lumbar spine) |
N40 | Somatosensory cortex |

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