Intra-epidermal electrically evoked potentials are sensitive to detect degenerative cervical myelopathy suggesting their spinothalamic propagation

Abstract

Objective

Degenerative cervical myelopathy (DCM) is a centromedullary spinal cord disorder mainly affecting crossing fibers. While contact heat evoked potentials (CHEPs) are sensitive in detecting DCM by testing spinothalamic integrity, somatosensory evoked potentials (dSSEPs) show unaffected dorsal column conduction. Intra-epidermal electrically evoked potentials (IEEPs) have unknown spinal propagation after noxious stimulation. We investigated (1) the spinothalamic tract propagation and (2) the discriminative power in detecting spinal pathology of IEEPs compared to CHEPs and dSSEPs in DCM.

Methods

DCM was diagnosed by neurological examination regarding stenosis (MRI). Stimulation of C6, C8, and T4 dermatomes yielded dSSEPs, CHEPs, and IEEPs. (1) Spinal propagation was assessed through concordant or discordant responses, and (2) discriminative power was determined using receiver operating characteristic curves (ROC).

Results

Twenty-seven patients (8F, 56 ± 12yrs) with DCM were analyzed and compared to age-matched healthy controls. IEEPs were abnormal in 43–54%, CHEPs in 37–69%, and dSSEPs in 4–12%. IEEPs showed high concordance with abnormalities of CHEPs (62–69%). ROC analyses showed good discriminative power of CHEPs and IEEPs contrary to dSSEPs.

Conclusions

The concordance of abnormal responses of CHEPs and IEEPs contrary to dSSEPs suggests spinothalamic propagation of IEEPs.

Significance

Minimal differences between CHEPs and IEEPs suggest complementary potential by the combined testing of spinothalamic tract integrity.