Splenius capitis is a reliable target for measuring cervical vestibular evoked myogenic potentials in adults.

Abstract

The cervical vestibular evoked myogenic potential (cVEMP) is a common and simple test of vestibulospinal reflex patency. In the clinic, cVEMPs are measured in response to loud sounds from the sternocleidomastoid (SCM) on the ventral neck, as subjects maintain an uncomfortable head posture needed to recruit SCM. Here we characterize the cVEMP in a dorsal neck turner (splenius capitis; SPL), and compare it with the SCM cVEMP. cVEMPs were recorded simultaneously via surface electromyography from SCM and SPL from 17 healthy subjects in a variety of postures, including head-turned postures adopted while either seated or standing, and the clinical posture. Like the SCM cVEMP recorded ipsilateral to the side of sound stimulation, the cVEMP on the contralateral SPL (synergistic with ipsilateral SCM) was characterized by a biphasic wave of muscle activity that began at~13ms. cVEMP reliability was higher on SPL vs. SCM in standing postures (chi-squared; P<0.05), and equivalent results were obtained from SPL in a standing or seated posture. In 9 of the 17 subjects, we also obtained bilateral intramuscular (IM) recordings from SPL at the same time as the surface recordings. In these subjects, the initial surface response in SPL was associated with a consistent decrease in multi-unit IM SPL activity. Overall, these results demonstrate that SPL recordings offer a complimentary target for cVEMP assessments. The expression of SPL cVEMPs in simple head-turned postures may also improve the utility of cVEMP testing for vestibular assessment in children, the elderly, or non-compliant.