Electrophysiologic identification and evaluation of stylohyoid and posterior digastricus muscle complex

• Published in: Journal of electromyography and kinesiology 2006-02, Vol.16 (1), p.58-65
• Main Authors: Kurt, Tülay, Gürgör, Nevin, Seçil, Yaprak, Yıldız, Nebil, Ertekin, Cumhur
• Format: Article
• Language: English
• Subjects: Action Potentials; Adult; Aged; Cranial reflexes; Electric Stimulation; Electromyography; Facial Nerve - physiopathology; Facial nerve conduction; Facial Paralysis - physiopathology; Female; Hemifacial Spasm - physiopathology; Humans; Magnetic stimulation; Magnetics; Male; Middle Aged; Neck Muscles - innervation; Neck Muscles - physiopathology; Stylohyoid and posterior digastricus muscle complex; Swallowing
• ISSN: 1050-6411; 1873-5711
• DOI: 10.1016/j.jelekin.2005.06.014

To identify the function of stylohyoid and posterior digastricus (STH–PD) muscle complex by the EMG techniques. Unaffected sides of the faces of 30 patients with facial paralysis or hemifacial spasm were investigated. A concentric needle electrode was inserted to the STH–PD muscle complex and another concentric needle electrode was inserted to the orbicularis oris (OO) muscle. Simultaneous recording were obtained from two muscles using electrical stimulation (ES) (in 25 cases) and magnetic coil stimulation (MS) (in 15 cases); and both in 10 cases. Afterwards, the function of STH–PD was studied such as whistling, lip purseing, swallowing, jaw opening and closing. (1) The motor latency of compound muscle action potential (CMAP) of the STH–PD muscle was shorter than that of OO. (2) When the facial nerve was stimulated more distally than the stylomastoid foramen, the CMAP elicited from the STH–PD muscle complex immediately disappeared. (3) Ipsilateral MS was able to elicit the motor evoked potential (MEP) from STH–PD either at intracranially (half of cases) or at the extracranially. While OO muscle was always stimulated intracranially by MS. (4) The STH–PD muscle complex could not be basically recruited by the mimicry except lip purseing. The main recruitment were provided by swallowing and jaw opening. Cortical MS were facilated during swallowing (5) Late reflex responses appeared in the STH–PD muscle complex during infraorbital-trigeminal and facial nerve ES. The STH–PD muscle complex is identified electrophysiologically. Although it is innervated by the facial nerve, its functions are mainly related with jaw opening and oropharyngeal swallowing. However, it is activated by the lip purseing.