Technical Aspects of Eliciting Trigeminocervical and Trigeminospinal Reflexes in Humans: A Scoping Review

This scoping review aims to summarize the technical strategies for obtaining trigeminocervical reflex (TCR) and trigeminospinal reflex (TSR) responses. Studies published on TCR or TSR elicitation in humans through electrical stimulation of trigeminal nerve branches were eligible for this scoping review. The data of interest included stimulation parameters, site of stimulation, recording parameters, and the feasibility of TCR and TSR elicitation, in healthy participants. Short-latency TCR responses were regularly obtained in both anterior and posterior neck muscles after electrical stimulation of the supraorbital and infraorbital nerves under voluntary muscle activation. However, without voluntary muscle activation, we found evidence of elicitation of short-latency TCR components only in the posterior neck muscles after supraorbital or infraorbital nerve stimulation. Long-latency TCR responses were regularly obtained in the anterior and posterior neck muscles in studies that evaluated this technique, regardless of the trigeminal branch stimulation or muscle activation status. Short-latency TSR components were not obtained in the included studies, whereas long-latency TSR responses were regularly recorded in proximal upper limb muscles. This scoping review revealed key heterogeneity in the techniques used for TCR and TSR elicitation. By summarizing all the methodological procedures used for TCR and TSR elicitation, this scoping review can guide researchers in defining optimized technical approaches for different research and clinical scenarios.