Eyelid Myokymia

Eyelid myokymia is the commonest type of facial myokymia. It is a condition that consists of spontaneous, gentle, constant, rippling contractions that spread through the affected striated muscle. The orbicularis oculi is the most affected muscle (Video). This condition is likely to be unilateral, affecting the lower eyelid more frequently than the upper eyelid. These contractions are self-limited, periodic, and lasting seconds to hours. Occasionally, the contractions become chronic and continue for several days or even a few weeks before resolving. Female gender and cold weather are risk factors for chronic eyelid myokymia. In rare cases, ipsilateral upper and lower eyelids involvement can occur at the same time. The eyelid consists of three lamellae (Fig). The anterior lamella consists of the skin and orbicularis oculi muscle. The middle lamella is a combination of the orbital septum, suborbicular fibro adipose tissue, and orbital fat. Lastly, the posterior lamella includes the tarsal plate, the retractors, and the conjunctiva. The orbicularis oculi ( OO ) muscle is a superficial striated muscle (Fig). It is directly responsible for eyelid closure. Its fibers interlock with a fibrous aponeurotic system that is directly attached to the dermis of the lid skin. The orbicularis oculi muscle has three portions, a pretarsal portion directly in front of the tarsal plates, a pre-septal portion over the orbital septum, and the orbital portion which extends to the eyebrow superiorly and the cheek inferiorly. It gets nerve supply from the temporal and zygomatic nerves, which are branches from the facial nerve. The medial upper and lower eyelid orbicularis oculi muscle receives innervation by the terminal superior branches of the buccal branch of the facial nerve.  The facial nerve originates from the brain stem (the pons). It divides within the parotid gland into the temporofacial and cervicofacial divisions. The temporal and zygomatic nerves (terminal branches from the temporofacial division) make upper and lower nerve plexuses that innervate the orbicularis oculi muscle. The terminal branches of the buccal facial nerve supply the medial upper and lower eyelid orbicularis muscle (Fig).