Abstract
PURPOSE: This study was conducted to report the histopathological and clinical features of the Marcus Gunn phenomenon and other similar conditions of upper eyelid misfiring. METHODS: This was a retrospective study of patients with congenital ptosis with Marcus Gunn phenomenon who have undergone surgical repair over a period of 12 years and another two patients with upper eyelid misfiring in association with extraocular movements to identify their histopathological findings as subtypes representing ocular congenital cranial dysinnervation disorder. RESULTS: Among 136 patients with congenital ptosis, 11 (8%) patients with Marcus Gunn phenomenon or misfiring were identified, of whom 9 (6.6%) had typical known Marcus Gunn phenomenon and 2 (1.4%) had eyelid misfiring similar to Marcus Gunn phenomenon. In all patients, the histopathological changes of the excised levator muscle included overall loss and/or atrophy of muscle fibers and irregular-modified Gomori trichrome staining. CONCLUSION: The Marcus Gunn phenomenon and similar misfiring conditions with synkinetic extraocular muscle movements share findings that are consistent with the neurogenic type of muscle atrophy. This result suggests a common underlying etiology with variable clinical findings, representing the ocular counterpart of congenital cranial dysinnervation disorder, which has been reported as ocular congenital cranial dysinnervation disorder.