Validity and Inter-rater Reliability fo the Vagus Nerve Neurodynamic Test Among Healthy Subjects

_A growing body of evidence has shown that the Vagus Nerve (VN) is not only the main anatomical structure responsible for the brain and guts communication but is also a target for many interventions in which drugs or classic treatments have failed. The VN cervical tract stimulation has reported positive results for high social burden problems like acute and chronic pain, psychiatric diseases, disturbs of consciousness and epilepsy. Also, it is well known that the selective tension of the Peripheral Nervous System, or neurodynamic test (NDT), is useful for diagnosis and treatment of neuropathic diseases and pain. Over the last 30 years NDTs were validated for upper and lower limb nerves but nowadays a VN-NDT is lacking and could be a potential alternative in diagnosis and treatment for critical or neglected conditions. Methods_ An estimated sample of 30 healthy participants will complete a questionnaire on vagal symptoms and perceived health status. A neurological assessment of the cervical tract will be performed before the test. The VN-NDT will be administered through a standardized sequence of physiological neck movements. Symptoms and heart rate (HR) will be monitored. Validity of NDT will be tested with ultrasonography assessment (C6-VN distance) during the tests administered by an expert and a novice. Motion of both assessors and subjects will be tracked through an infra-red optoelectronic system. Inter-examiner accordance will be obtained and comparisons between assessors' positive and negative tests due to symptoms provocation and reduction (Cohen's Kappa) will be performed. A two-way analysis of variance (ANOVA) will be performed with factors experience and side tested (2 × 2). Receiver operating characteristic (ROC) curves will be adopted to define the accuracy, sensitivity, specificity, positive and negative likelihood ratios of the VN-NDT in autonomic dysfunction symptoms detection and on perceived health status.Results_ It is expected to determine the inter-examiner accordance and to not detect significant assessors effects on test results. It is also expected to detect a change of the C6-VN distance and HR during the test and to estimate the accuracy of the test for autonomic dysfunctions detection.Conclusions_ Normative physiological values parameter variations at the administration of the VN-NDT are fundamental to determine the hallmarks needed to screen clinical and preclinical conditions involving autonomic dysfunctions_

Inclusion criteria

• Subjects aged between 18 and 70 years old
• Subjects that have signed the written informed consent

Exclusion criteria

• Subjects with significant neck pain or headache (with NRS greater than 3/10)
• Pregnancy
• Recent neck surgery or significant trauma in the preceding 3 months
• Cancer or inflammatory disorders spinal cord or cauda equina signs
• Widespread neurological disorders affecting the tone of upper limb and neck muscles
• Underlying diseases, such as diabetes mellitus.