What is the role of somatosensory evoked potentials (SEPs) in the workup of multiple sclerosis?

Updated: Oct 25, 2019
  • Author: Andrew B Evans, MD; Chief Editor: Selim R Benbadis, MD  more...
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The SEP is positive in a number of patients with multiple sclerosis (MS). Abnormalities may include prolonged latencies or lack of development of the SEP. Lower-extremity studies are more often abnormal because of the longer pathway. Upper-limb SLSEPs are abnormal in about 40-60% of MS patients; lower-limb SLSEPs have an abnormality rate of about 70%, presumably because of the greater length of white matter involved. American Academy of Neurology (AAN) guidelines suggest that SEPs may be useful for diagnosing clinically silent MS lesions. [48]

Eisen et al reported abnormal results in trigeminal nerve stimulation in 41% of patients with MS. [49] Abnormalities of trigeminal SLSEPs have also been reported in patients who had MS, Wallenberg syndrome, cerebellopontine angle tumors, trigeminal neurinomas, or meningeal sarcoidosis with facial paralysis.

Approximately one third of SLSEP abnormalities in MS are unilateral. One fifth of the bilateral abnormalities are asymmetric. Some patients with MS show loss of N/P13 with preservation and normal latency of N19; this pattern is difficult to explain if SLSEP generator sources are assumed to be linked in series.

Comparisons of SEP, visual evoked potential (VEP), and brainstem auditory evoked potential (BAEP) have found that VEP testing and SEP testing are about equally sensitive for revealing clinically unsuspected lesions and that BAEP is one half to one third less sensitive. The 3 tests should be viewed as complementary.

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