[Value of simultaneous electromyographic recording of the levator palpebrae and the orbicularis oculi muscles as an early diagnostic marker for blepharospasm]

Abstract

Introduction: Blinking is usually a spontaneous movement that takes place as a consequence of the alternating and antagonistic activity of the orbicularis oculi and levator palpebrae superioris muscles. In order to achieve an efficient movement, they are regulated by a reciprocal inhibition in such a way that the agonistic movement triggers the simultaneous inhibition of the antagonist, and vice-versa. Co-contraction is the dysfunction of this mechanism and is a significant phenomenon in dystonic disorders, especially in simple movements that are not subject to variability, as is the case of blinking. Blepharospasm is the most frequent dystonia affecting adults and it is easy to diagnose. In incipient processes it may offer some difficulties and can even be mistaken for other processes. We evaluate the possibility of an early diagnosis of blepharospasm in patients with palpebral hyperfunction with a short time to progression.

Patients and methods: A prospective evaluation of 23 patients with suspected blepharospasm was conducted. Each of them was submitted to a simultaneous electromyographic study of the orbicularis oculi and levator palpebrae muscles.

Results: The presence of co-contraction in any of the blinking movements recorded was related with the chances of developing blepharospasm in the following years. None of the patients who did not have dystonic blinking presented blepharospasm in the years of the follow-up; in contrast, it was developed by all of those who presented it on some occasion.

Conclusions: Dystonic blinking was observed in all the patients with blepharospasm, and blinking was physiological in those who did not present it. Simultaneous electromyographic evaluation of the muscles of the eyelids is a simple, sensitive, well-tolerated and particularly specific examination that can be used to determine whether a patient will show blepharospasm in an early stage of development.