Introduction
Cervical Vestibular Evoked Myogenic Potentials (cVEMP) are an increasingly important tool in the assessment of vestibular and central nervous system integrity. While traditionally used to evaluate peripheral vestibular function, emerging evidence highlights the value of cVEMP in detecting central disorders affecting the brainstem and cerebellar pathways. This article summarizes the principles, clinical applications, and recent findings regarding cVEMP in central pathologies.
Physiological Basis of cVEMP
The cVEMP response is a short-latency inhibitory potential recorded from the sternocleidomastoid muscle following sound or vibration stimulation. The reflex arc involves the saccule, the inferior vestibular nerve, the vestibular nuclei in the brainstem, the medial vestibulospinal tract, and the spinal accessory nerve. Any disruption at these central stations can alter the cVEMP waveform, providing a window into brainstem and cerebellar function.
cVEMP in Central Disorders
In patients with multiple sclerosis, cVEMP abnormalities—such as prolonged latency or absent responses—correlate with brainstem lesions on MRI. Similarly, in cerebellar degeneration and stroke involving the brainstem, cVEMP parameters are frequently altered. The test also shows promise in Parkinson's disease, where central processing deficits may be detected before clinical signs are overt.
Methodological Considerations
Standard cVEMP protocols use air-conducted tone bursts (usually 500 Hz) or bone-conducted vibration. Key parameters include latency, amplitude, and the presence of the p13 and n23 peaks. In central disorders, attention to correction for muscle tonic contraction and age-related normative data is essential to avoid misinterpretation.
Interpreting cVEMP in Central Pathologies
Prolonged p13 latency is a hallmark of delayed central conduction, often seen in demyelinating conditions. Asymmetries between ears may point to unilateral brainstem lesions. Additionally, amplitude asymmetry ratios exceeding 50% suggest unilateral vestibular or central imbalance. Clinicians must correlate cVEMP findings with neuroimaging and other vestibular tests like oVEMP, vHIT, or caloric irrigation.
Future Directions
Advanced protocols, including tone burst vs. click stimuli and electrode montages, continue to refine the specificity of cVEMP for central disorders. Automated analysis algorithms and machine learning offer potential for more objective detection of subtle central abnormalities. The integration of cVEMP into routine neuro-otological assessment will likely expand as evidence for its utility in central nervous system disorders grows.
Conclusion
cVEMP testing provides a non-invasive, readily available electrophysiological measure of brainstem and cerebellar function. Its role in evaluating central disorders is supported by a growing body of literature. When interpreted within the appropriate clinical context, cVEMP can guide diagnosis, monitor disease progression, and aid in the differentiation of peripheral vs. central vestibular pathology. Continued research and standardization are needed to fully harness its diagnostic potential.