Fenomenul Marcus Gunn: managementul si rezultatele tratamentului in 19 cazuriAfectiune congenitala, caracterizata prin ptoza unei pleoape. La deschiderea sau la miscarea gurii, pleoapa ptozata se ridica pentru un moment, asemanator clipitului.

Se pare ca este datorata unei inervatii anormale a muschiului levator de catre nervul trigemen.

Fenomenul Marcus Gunn este o malformatie congenital si const in mobilizarea sinkinetic a pleoapei superioare asociat cu miscarea mandibular si ptoz. Pleoapa superioar acoper pupila, dar la deschiderea gurii sau deplasarea antero-lateral, ctre partea neafectat se produce o ridicare sinkinetic a pleoapei afectate.

Acest fenomen este de obicei unilateral, mai frecvent pe partea stang. Intensitatea simptomelor este variabil.Cazurile ce prezint simptomatologie minim nu necesit tratament chirurgical spre deosebire de acele cazuri cu simptomatologie avansat care beneficiaz de tratament chirurgical.

Scopul tratamentului chirurgical este de a elimina miscarea sinkinetic a pleoapei si de a corecta ptoza. Tratamentul acestor dou semne clinice se realizeaz prin transsectia muschiului levator al pleoapei (incizia in santul fronto-palpebral) si resuspendarea pleoapei la muschiul frontal prin intermediul benzilor musculare ale muschiului levator al pleoapei superioare.

Fenomenul Marcus Gunn a fost diagnosticat la 17 pacienti la scurt timp postnatal si la 2 pacienti la 9 luni de viat.Miscarea sinkinetic a pleoapei superioare cu deschiderea arcadelor dentare poate fi asociat in 4-6% din cazuri cu blefaroptoz congenital.

Aceast sinkinezie patologic este cauzat de o posibil anastomoz intre nervul oculomotor si nervul maseterin. Dup unii autori, acest fenomen ar fi mai mult de cauz functional decat anatomic. Alti autori consider c acest fenomen este un reflex ce afecteaz fibre aferente senzitive ale nervului mandibular si fibre eferente ale nervului oculomotor.

Sindromul Marcus Gunn este o conditie ce tinde s regreseze in adolescent. Adultii sunt capabili s controleze aceast sinkinezie.

Bartkowski BS, Zapala J, Wyszynska-Pawelec G, Krzystkowa M.K: Marcus Gunn Jaw - Winking phenomenon: management and resultsof treatment in 19patients. J Cr-Max Fac Surg 27: 25-29, 1999.Marcus Gunn phenomenonMarcus Gunn phenomenon

Classification and external resources

Nerves of the orbit, and the ciliary ganglion. Side view. (Trigeminal nerveandoculomotor nerveboth visible)

OMIM154600

eMedicinearticle/1213228

Marcus Gunn phenomenon(a.k.a. Marcus Gunn Jaw-Winking[1]

HYPERLINK "http://en.wikipedia.org/wiki/Marcus_Gunn_phenomenon" \l "cite_note-pmid18415867-1"[2]or Trigemino-oculomotor Synkineses) is anautosomal-dominantcondition withincomplete penetrance, in which nursing infants will have rhythmic upward jerking of their upper eyelid. This condition is characterized as asynkinesis: when two or more muscles that are independently innervated have either simultaneous or coordinated movements.

Common physiologic examples of synkineses occur during sucking, chewing, or conjugate eye movements. There are also several abnormalcranial nervesynkineses, both acquired and congenital. Marcus Gunn jaw-winking is an example of a pathologic congenital synkinesis.

First described by the ophthalmologistMarcus Gunnin 1883,[3]this condition presents in approximately 5% of neonates with congenitalptosis. This condition has been associated withamblyopia(in 54% of cases),anisometropia(26%), andstrabismus(56%).

PathophysiologyIt has been postulated that the synkinesis is due to damage to cranial nerve nuclei, caused by peripheral nerve injury and the nuclear lesion releases evolutionarily older [neural] mechanisms with their tendency toward associated movements, and so primitive reflexes are not inhibited.

Marcus Gunn jaw-winking is an exaggeration of a very weak physiologic co-contraction that has been disinhibited secondary to a congenital brain stem lesion. The stimulation of the trigeminal nerve by contraction of the pterygoid muscles of jaw results in the excitation of the branch of the oculomotor nerve that innervates the levator palpebrae superioris ipsilaterally (on the same side of the face).

There are two major groups of trigemino-oculomotor synkineses:1) External pterygoid-levator synkinesis is when the eyelid raises upon:

Jaw thrust to opposite side (homolateral external pterygoid)

Jaw is projected forward (bilateral external pterygoid)

Mouth is opened widely

2) Internal pterygoid-levator synkinesis is when the eyelid raises upon teeth clenching

External pterygoid-levator synkinesis is the more common group.

TreatmentTreatment is usually unnecessary. In severe cases, surgery with a bilateral levator excision and frontalis brow suspension may be used.[4]Behavioral and Social ImplicationsAlthough treatment may be unnecessary, there may be social implications, especially in young children when venturing from a supportive home environment to a public environment (e.g., starting school). Continued support, including monitoring behavior and educating the child about his or her appearance as seen by others, is encouraged. Gradual or sudden withdrawal from interaction with others is a sign that may or may not be related to such behavior. Studies are being conducted to elucidate these implications.

Inverse Marcus Gunn PhenomenonInverse Marcus Gunn phenomenon is a rare condition[5]that causes the eyelid to fall upon opening of the mouth. In this case, trigeminal innervation to the pterygoid muscles of the jaw is associated with an inhibition of the branch of the oculomotor nerve to the levator palpebrae superioris, as opposed to stimulation in Marcus Gunn jaw-winking.

References1. ^Yamada K, Hunter DG, Andrews C, Engle EC (September 2005)."A novel KIF21A mutation in a patient with congenital fibrosis of the extraocular muscles and Marcus Gunn jaw-winking phenomenon".Arch. Ophthalmol.123(9): 12549.doi:10.1001/archopht.123.9.1254.PMID16157808.2. ^Cates CA, Tyers AG (2008)."Results of levator excision followed by fascia lata brow suspension in patients with congenital and jaw-winking ptosis".Orbit27(2): 839.doi:10.1080/01676830701376072.PMID18415867.3. ^Gunn RM. Congenital ptosis with peculiar associated movements of the affected lid. Trans Ophthal Soc UK. 1883;3:283-7.

4. ^Ibrahim HA (2007)."Use of the levator muscle as a frontalis sling".Ophthal Plast Reconstr Surg23(5): 37680.doi:10.1097/IOP.0b013e3181379e20.PMID17881988.5. ^Prakash MV, Radhakrishnan M, Yogeshwari A, Nazir W, Maragatham K, Natarajan K (June 2002)."Inverse Marcus Gunn phenomenon".Indian J Ophthalmol50(2): 1424.PMID12194575.[