Echography-guided Botulinum Toxin for Moving Ear Syndrome

A 55-year-old man presented with brief backwards contractions of his right ear that began 4 months prior and progressively worsened, recurring several times per day. Ear movements were involuntary, partially suppressible, persistent during sleep, and associated with a feeling of “inner tension” and discomfort that radiated to the ipsilateral occipito-mastoid region (Video).

Medical history revealed cranio-facial trauma with brain injury at 11 years, which resulted in left parieto-temporal encephalomalacia and ipsilateral cranioplasty. Since the age of 53, the patient has been effectively treated with carbamazepine 800 mg/day for focal-onset seizures with right upper limb paresthesia.

Baseline needle electromyography revealed spontaneous tonic activity in the right posterior auricularis muscle with 500 ms bursts of normal motor unit potentials (longer than previously reported) observed during ear movements [1].

A diagnosis of Moving Ear Syndrome (MES) was formulated and ten units of onabotulimtoxin A were injected into the muscle using a combined electromyographic-ultrasound guidance. After two weeks, discomfort resolved, and both frequency and amplitude of ear movements decreased, disappearing during sleep and occurring rarely during the day. At 12 weeks, while ear movements were slowly resuming during the day, a follow-up electromyography displayed a significant reduction in spontaneous tonic activity with occasional bursts(Supplementary figure).

The external ear muscles (anterior, superior, posterior) are vestigial muscles innervated by the facial nerve, which only 1 in 5 people can voluntarily activate. MES is a rare hyperkinetic disorder characterized by involuntary contractions of the external ear muscles, that may be rhythmic (1–2 Hz), unilateral or bilateral, and associated with pain [1]. Some authors have labeled ear movements as tics for partial voluntary suppressibility [1], while others described them as dystonic or myoclonic phenomena [2]. MES has been associated with neuroactive drugs including paroxetine, bromopride, chlorpromazine, and methylphenidate [2].

In this case, the feeling of inner tension and partial voluntary suppression are consistent with tics, whereas the spontaneous tonic activation, persistence during sleep, and rapid improvement following botulinum toxin argue in favor of facial nerve hyperexcitability, which might be post-traumatic, yet without neurogenic findings at needle electromyography.

Given the complex pathophysiology of MES, traditional pharmacological treatments (clonazepam, baclofen, pregabalin, propranolol) may be unsatisfying, while botulinum toxin and the anecdotal use of pallidothalamic tractotomy have proven to be effective [3].

Notably, the use of ultrasound combined with electromyographic guidance for botulinum toxin injections can enhance the precision of administration and reduce the risk of vascular injury. Although MES is rare and not typically disabling, early treatment can significantly improve quality of life with minimal risks.