AAEM minimonograph 19: Somatosensory evoked potentials

Diagnostic validity of somatosensory evoked potentials in subgroups of patients with sciatica

“…Positive L4, L5, or S1 SEP therefore strongly indicate corresponding true nerve root compromise. The results also indicate that the true-positive rate is higher in patients with facet joint hypertrophy than in patients with disc pathology alone, in agreement with the view that SEP may be useful in patients with spinal stenosis [33,49,52], but less useful in patients with disc pathology without elements of bony entrapment [1,5,14,53]. Some of the variations between the results obtained in previous studies may be related to different prevalences of bony entrapment in the patients included in the study, since some of the studies reporting usefulness of SEP in patients with low back pain and sciatic radicular symptoms did not exclude patients with stenosis of the spinal canal or lateral recesses [30,31,46].…”

“…The segmental specificity of the sensory nerves used for stimulation in the present study is better than that of mixed nerves, but is not perfect [5,18,19,40]. P1 latency prolongation might therefore be more strongly associated with compromised nerve roots with than without a compromised neighboring nerve root.…”

“…One recent review concludes with a negative recommendation of dermatomal SEP [3]. Another assumes that dermatomal SEP may be more helpful in the evaluation of patients with lumbar spinal stenosis than of patients with unilateral, unilevel radiculopathies, but doubts that SEP elicited by cutaneous nerve stimulation have any role in the diagnosis of radiculopathies [5]. Finally, a third review suggests that both dermatomal and sensory nerve SEP may be useful in the assessment of chronic multilevel multiple rootlet disease, but not in the evaluation of acute radiculopathy [1].…”

Intraoperative somatosensory evoked potentials to facilitate peripheral nerve release

“…11 Regarding the LFCN, one limitation lies in the fact that this nerve is purely sensory, precluding the use of usual motor nerve stimulation patterns. Nevertheless, LFCN cutaneous supply zone stimulation is possible 7,12 according to techniques published previously, 13 and recently refined. 8 Moreover, others have demonstrated the ability to determine the extent of the LFCN cutaneous supply zone (by needle stimulation) and the saphenous nerve cutaneous supply zone (by transcutaneous stimulation).…”

Median nerve SEP after a high medullary lesion: preserved N18 and absent P14 components (case report)

“…The recent descriptions of selected cases with well defined lesions at the high medulla, showing preservation of the N18 component 9,13 , suggest that indeed the lower medulla is capable of generate the N18 component. However, some contradictions still persists 15 and this point does not seem to be universally accepted 16 . In view of this picture we believe that it is pertinent to report the SEP findings of another case with a lesion at high medullary level.…”