Marin-Amat syndrome: a rare facial synkinesis.

Dear Editor,

Marin Amat syndrome is a rarely reported synkinesis in which eyelids close upon full opening of the jaw or movement of the jaw laterally. 1 The eye closure occurs only with wide jaw opening and it is felt that the disorder represents aberrant regeneration within the facial nerve with proprioceptive impulses associated with muscle stretch acting as the trigger.2 In inverse Marcus Gunn phenomenon the upper lid falls to cover the eye with movements of mastication.3 This is more commonly seen as an acquired rather than congenital anomaly in central nervous system (CNS) disease.

A 24-year-old girl presented with complaints of involuntary closure of left eye on smiling. She had a history of facial palsy at the age of three years. She had recovered fully since then. On ocular examination, she had a visual acuity of 20/20 in both eyes. Both eyes had a normal anterior and posterior segment. On attempted opening of mouth or smile, a closure of left eye was noted. The closure was due to the blepharospasm rather than ptosis or drooping [Fig. 1]. An electromyography, however, would have been confirmatory.

Figure 1

Various photographs of the patient showing normal as well as blepharospasm-like movement of left lids on opening of mouth. Note that the intensity of closure is almost proportional to the opening of the mouth

Marcus Gunn jaw-winking is thought to be a form of synkinetic ptosis. An aberrant connection appears to exist between the motor branches of the trigeminal nerve innervating the external pterygoid muscle and the fibers of the superior division of the oculomotor nerve that innervate the levator palpebrae superioris (LPS) muscle of the upper eyelid. Inverse Marcus Gunn phenomenon is the opposite of Marcus Gunn phenomenon where the eyelid drops on moving the jaw.1,3 Though Marin Amat syndrome has been occasionally termed as inverse Marcus Gunn phenomenon,1 a few authors have argued against this.3,4 The Marin Amat syndrome represents patients with a connection between the orbicularis oculi and not with LPS. Electromyographic studies4 have clearly shown that the closing of the involved eye on opposite motion of the lower jaw was not mediated by seventh nerve stimulation of the orbicularis oculi but by inhibition of the homolateral LPS. As a consequence of this observation, a specific and effective operation could be planned.

Here, the clinical findings in both the syndromes would be quite different. Inverse Marcus Gunn phenomenon would have ptosis and therefore drooping of eyelid secondary to relaxation of LPS, whereas Marin Amat syndrome would have more of a blepharospasm like closure secondary to action of orbicularis oculi. For inverse Marcus Gunn phenomenon, the most commonly accepted hypothesis is that an abnormal nervous connection exists in the CNS between the nerve supply of the LPS and the associated muscle. The LPS is perhaps innervationally connected not only with the third nucleus but also with the external pterygoid portion of the fifth nucleus. The exact level of this anomalous connection is disputed.3 For the Marin Amat syndrome, the synkinesis is caused by aberrant regeneration of the seventh nerve with sprouts of axons supplying more than one muscle group [Table 1].3,4

Table 1

The various differences between the Marcus Gunn jaw wink, inverse Marcus Gunn and Marin Amat syndromes

Treatment may not be necessary for patients with a slight degree of deformity in cases of inverse Marcus Gunn phenomenon. For acute cases, bilateral frontalis sling with disinsertion of the LPS has been suggested.5 For patients with the Marin Amat syndrome, since the patients almost represent blepharospasm, botulinum toxin may be helpful.