|Year : 1992 | Volume
| Issue : 1 | Page : 20-23
Unusual Marcus Gunn phenomenon in adults
SM Betharia, Kamal Kishore, Harsh Kumar
Dr Rajendra Prasad Centre for Ophthalmic Sciences, All Institute of Medical Sciences, Ansari Nagar, New Delhi, India
S M Betharia
Dr Rajendra Prasad Centre for Ophthalmic Sciences, All Institute of Medical Sciences, Ansari Nagar, New Delhi 110 029
Source of Support: None, Conflict of Interest: None
Two unusual cases of Marcus Gunn phenomenon in adults are presented. The first case was characterised by a bilateral jaw-winking phenomenon along with an asymmetric bilateral congenital ptosis, whereas the second case had bizarre spontaneous movements of the affected lid, deficient abduction and pseudoptosis in association with jaw-winking. The pathogenesis of Marcus Gunn phenomenon is discussed.
|How to cite this article:|
Betharia S M, Kishore K, Kumar H. Unusual Marcus Gunn phenomenon in adults. Indian J Ophthalmol 1992;40:20-3
| Introduction|| |
Marcus Gunn phenomenon  is seen in 4 to 6% of congenital ptosis patients ,,, It is believed to be a neural misdirection syndrome. in which fibres of the motor division of the trigeminal nerve are congenitally misdirected into the superior pterygoid and the levator muscles. This has been demonstrated on electromyographic studies . There is a belief that the jaw-winking ptosis has a tendency to improve with age ,,,,, and this may be a reason why it is rarely seen in adults. The condition is almost always unilateral, usually involves the left side and is associated with ipsilateral superior rectus underaction in approximately 80% of the cases .
We are reporting two unusual cases of Marcus Gunn phenomenon in adults; one with bilateral Marcus Gunn phenomenon, and the other with spontaneous asymmetric movements of the ptotic lid. Left eye was involved in Case 1 and the right eye in Case 2.
| Case reports|| |
Case 1: An 18-year-old female patient presented with complete ptosis of the left upper lid since birth and alternate movement of the lids while eating. There was 4mm of ptosis in the left eye with no demonstrable levator function, and underaction of the ipsilateral superior rectus muscle. On moving the jaw to the right side, the left eyelid elevated and the lid margin touched the limbus while the lid margin of the right eye was at the pupillary margin [Figure - 1]. On moving the jaw to the left side the left eyelid drooped to exhibit 4 mm ptosis whereas the right eyelid elevated by two millimeters to reach the limbus [Figure - 2]. These findings clearly demonstrate bilateral jaw-winking ptosis. Orthoptic examination revealed absence of binocular vision and alternate suppression. Rest of the ocular examination and the visual acuities were normal on both sides.
Case 2: An 18-year-old male patient presented with the complaints of drooping of the right upper lid and abnormal movements of the same lid since early childhood. There was no history of birth trauma or any significant illness in the past.
On examination, the right eye was amblyopic with a best corrected visual acuity of 6/36. There was complete ptosis on the right side with no demonstrable levator function [Figure - 3]. There was considerable lid leg in down gaze [Figure - 4] The jaw-winking phenomenon was seen on opening the mouth [Figure - 5]. There was 30 degrees of right hypotropia in the primary gaze [Figure - 6] along with double elevator palsy and absence of Bell's phenomenon [Figure - 7][Figure - 8]. The abduction of the right eye was deficient. Strong elevation of the lid was noted on attempted abduction [Figure - 9]. Other ocular movements were normal. The abnormal lid movements noted in this case were spontaneous lift of the right upper lid without any movement of the jaw or clenching of teeth [Figure - 10]. These movements were constant but variable in amplitude and were most prominent in down gaze.
These spontaneous movements were considerably minimised when the patient's left eye was covered and fixation was taken up by the right eye. The palpebral aperture also opened to a nearly normal extent on taking up fixation [Figure - 11]. A see-saw like action of the two lids was frequently observed in which normal blinking closure of the left upper lid was accompanied by a rather wide opening movement of the right upper lid. The elevation of the ptotic lid was, however, momentary.
| Discussion|| |
Although Marcus Gunn's original report was based on an adult patient , there is a belief among some authorities that the jaw-winking ptosis has a tendency to improve with age  because the syndrome is rarely encountered in adults. A well-documented vertical study of these patients followed up without surgery to prove that the Marcus Gunn phenomenon decreased or vanished with age is still awaited  The condition is said to be associated with a weakness of the superior rectus muscle on the affected side in about three out of four instances . The incidence of superior rectus palsy and double elevator palsy was, however, found to be 23% and 25% respectively in a recent review on the Marcus Gunn phenomenon . The cause of double elevator palsy is not known. It may be caused by a supranuclear lesion ,. Similarly, a supranuclear lesion has been postulated to be responsible for the jaw-winking reflex as well . Our case had double elevator palsy.
Case 1 was unique as it was an adult patient showing bilateral Marcus Gunn phenomenon along with a predominantly left sided ptosis. There was a see-saw like movement of the upper lids when the jaw was moved from side to side. Bilateral jaw-winking is an extremely rare condition ,,,. The pathogenesis of these cases seems to involve bilateral misdirection of the Vth nerve fibres into the Illrd nerve nuclei during the period of embryogenesis. This may be explained on the basis of close proximity of the motor nucleus of the Vth nerve and the Illrd nerve nucleus during early development .
Previous histopathological studies performed on the levator muscles of patients suffering from unilateral jaw-winking have revealed normal appearing muscle fibres . This led some authors to conclude that the Marcus Gunn phenomenon represented an "abnormal innervation of a normal muscle . However, a pattern of bilateral but asymmetric neurogenic atrophy has recently been demonstrated on histopathological studies using newer histochemical techniques . The authors postulated that the initiating pathological process responsible for the Marcus Gunn phenomenon was probably located within the central nervous system 
Case 2 had peculiar features such as spontaneous movements of the upper lid, widening of the palpebral aperture on fixation and on attempted abduction. Spontaneous movements observed in our patient could have a pure nuclear or supranuclear origin. Widening of the palpebral aperture on attempted abduction could possibly be due to misdirection of fibres destined for the lateral rectus to the lllrd nerve nucleus or to its intranuclear tract. There was no retraction of the globe on abduction, thus differentiating the condition from Duane's retraction syndrome. However, an association of jaw-winking with the Duane's retraction syndrome has also been described recently 
Wide opening of the palpebral aperture on fixation could also be due to a central mechanism. The inhibition of abnormal movements on fixation is difficult to explain. It is possible that the abnormal neural pathway responsible for the spontaneous movements in this suppressed eye was overridden by strong fixation impulses when the eye was forced to take up fixation after covering the opposite eye.
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[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7], [Figure - 8], [Figure - 9], [Figure - 10], [Figure - 11]