Electromyography of Extrinsic and Intrinsic Ear Muscles in Healthy Probands and Patients with Unilateral Postparalytic Facial Synkinesis

Abstract

There are currently no data on the electromyography (EMG) of all intrinsic and extrinsic ear muscles. The aim of this work was to develop a standardized protocol for a reliable surface EMG examination of all nine ear muscles in twelve healthy participants. The protocol was then applied in seven patients with unilateral postparalytic facial synkinesis. Based on anatomic preparations of all ear muscles on two cadavers, hot spots for the needle EMG of each individual muscle were defined. Needle and surface EMG were performed in one healthy participant; facial movements could be defined for the reliable activation of individual ear muscles’ surface EMG. In healthy participants, most tasks led to the activation of several ear muscles without any side difference. The greatest EMG activity was seen when smiling. Ipsilateral and contralateral gaze were the only movements resulting in very distinct activation of the transversus auriculae and obliquus auriculae muscles. In patients with facial synkinesis, ear muscles’ EMG activation was stronger on the postparalytic compared to the contralateral side for most tasks. Additionally, synkinetic activation was verifiable in the ear muscles. The surface EMG of all ear muscles is reliably feasible during distinct facial tasks, and ear muscle EMG enriches facial electrodiagnostics.

Assessment of Vestigial Auriculomotor Activity to Acoustic Stimuli Using Electrodes In and Around the Ear

“…This was also observed in the current study, and led to rejecting data from experiment 2 during which participants were talking, as the EMG generated when speaking was clearly visible in signals obtained from the electrodes placed in and around the ear. Overall, activity generated by such movement can, however, be excluded as a possible confounding factor for the current results, since they do not induce lateralized activity at the auricular muscles (Rüschenschmidt et al, 2022).…”

“…Strauss et al (2020) also demonstrated that additional auricular muscles, such as the anterior and transverse auricular muscle (AAM and TAM), are co-activated during their exogenous attention experiment, which mainly corresponds to the current study's experiment 1. Furthermore, co-activation of intrinsic and extrinsic auricular muscles can be observed in non-listening related tasks, such as smiling or nose wrinkling (Rüschenschmidt et al, 2022). Given the central position of the in-ear electrodes, it seems possible that they pick up activity from several auricular muscles, both intrinsic and extrinsic, and are not exclusively recording EMG from the PAM.…”

Pathogenesis, diagnosis and therapy of facial synkinesis: A systematic review and clinical practice recommendations by the international head and neck scientific group

“…The most common complaint of facial synkinesis is unintentional eye narrowing or closure during voluntary mouth movements (e.g., smile, kiss, or blowing) or, vice versa, unintentional midface muscle contraction during voluntary eye closure (oculo-oral synkinesis; Figure 2 ). Synkinesis can be present in all facial muscles including the platysma, leading to uncomfortable neck contraction ( 35 ), and even the external and internal ear muscles ( 36 ). When intra-temporal or a more proximal lesion occurs, stapedial synkinesis can occur, leading to changes in the hearing threshold ( 37 ).…”

Special Issue: Evidence-Based Diagnosis and Management of Facial Nerve Disorders

“….] develop a standardized protocol for a reliable surface EMG examination of all nine ear muscles in twelve healthy participants" [5] which was then applied "[. .…”

“….] in seven patients with unilateral postparalytic facial synkinesis" [5]. Following that, we can also provide information about more recently developed methods, like the possibility of facial nerve palsy diagnostics via "[.…”