Between Ptosis and Mandibular Contraction, there is a Hidden Marcus Gunn Syndrome

INTRODUCTION Marcus Gunn syndrome or unilateral trigemino-oculomotor syncinesis is a very rare autosomal dominant genetic disorder characterised by a combination of congenital ptosis and mandibulopalpebral syncinesis during certain mandibular movements. The Marin Amat phenomenon is an autosomal dominant disorder which is the reverse of Marcus Gunn syndrome, i.e. the closure of one eye caused by a wide opening of the mouth, was described by Marin Amat in 1918. OBJECTIVES AND METHODS This is a description of a case series from the ophthalmology department of the CHU Mohammed VI d'Oujda, with the aim of describing the etiopathogenic, clinical and therapeutic aspects of Marcus Gunn syndrome. OBSERVATIONS We report a series of two cases of children with Marcus Gunn syndrome. Case 1: A 5-year-old boy with no previous pathological findings presented with unilateral ptosis of the left upper eyelid at the age of 4 months. His visual acuity was 10/10 in right eye on the right and 5/10 in left eye. Appendages showed ptosis on the left with no upper palpebral crease, and no associated oculomotor paralysis or strabismus. Examination of the anterior and posterior segments was unremarkable in both eyes. We observed retraction of the upper eyelid when opening the mouth and chewing. Second case: a 7-year-old girl, brought in by her parents for a ptosis of the left eye noted at birth. This is a 7-year-old girl brought in by her parents for ptosis of the left eye, diagnosed at birth. She had no particular pathological antecedents. Her visual acuity was 10/10 in right occlusion and 3/10 in left occlusion. Adnexal findings included partial ptosis of the left eye, with retraction of the upper eyelid when opening the mouth and chewing. The rest of the ophthalmological examination was unremarkable. We noted amblyopia on the left, and the somatic examination was unremarkable in both children. Orbital and head CT scans were normal in both children. Both children had undergone sectioning of the superior levator muscle with frontal suspension using prolene sutures, with good progression, followed by total optical correction and treatment of the amblyopia. DISCUSSION Marcus Gunn syndrome is a very rare condition, affecting 2-13% of cases of congenital ptosis. The first case was described by British physician Robert Marcus Gunn in 1883 as the “blinking jaw phenomenon”. It is characterized by unilateral ptosis associated with mandibulo-palpebral synkinesis, i.e. ptosis that is corrected by mouth opening or mandibular diduction. It may be isolated or associated with oculomotor disorders. Our two cases present a clinical picture that corroborates the description in the literature. Marcus Gunn syndrome is an autosomal dominant genetic disorder, but it can also occur under certain conditions (following childhood trauma, inflammatory processes or even tumour lesions). The etiopathogenesis is poorly understood, but is probably due to aberrant innervation of the levator muscle of the upper eyelid by trigeminal motor fibers, according to the literature. The result is a congenital brainstem lesion that leads to disinhibition of mandibulo-palpebral co-contraction, which is physiologically very weak and inhibited. Stimulation of the trigeminal nerve by contraction of the pterygoid jaw muscles excites the branch of the oculomotor nerve that innervates the levator of the upper eyelid, causing rhythmic upward jerking of the upper eyelid. CONCLUSION Marcus Gunn syndrome is a rare condition characterized by congenital ptosis and mandibulo-palpebral syncinesia. Its etiopathogeny remains poorly elucidated. Its management is an absolute emergency, as the occurrence of amblyopia depends on it. The choice of surgical technique is difficult, as it must correct both ptosis and syncinesia. BIBLIOGRAPHICAL REFERENCE 1. Awan KJ.Marcus Gunn (jaw-winking) syndrome. Am J Ophthalmol. 1976 Sep;82(3):503-4. Google 2. Nan Xiang, Wei-Kun Hu, Bin Li, Rong Liu. Management of morderate-to-severe Marcus-Gunn syndrome by anastomosis of levator and frontal muscles. Int J Ophthalmol. 2010;3(4):342-345. Google 3. 4. Beard D C. A new treatment for severe unilateral congenital ptosis and for ptosis with jaw-winking. Am J Ophthalmol. 1965 Feb;59:252-8. Google 5. Altman K. The Marcus Gunn (jaw-winking) phenomen: a case report. Br J Oral Maxillofac Surg. 1990 Feb;28(1):53-4. PubMed | Google Scholar