Mandibular transient syndrome, also known as Marcus Gunn syndrome, is a less common co-movement of the upper eyelid and jaw, a disease syndrome in which the patient has unilateral ptosis and superior rectus muscle insufficiency, but the ptosis can disappear with jaw movements such as mouth opening and chewing. The cause of the condition is not yet understood. It is generally believed that the disappearance of ptosis when the mouth is opened or chewed may be due to an abnormal connection between the patient’s motoneurone fibers, which innervate the levator muscle, and the motor branch of the trigeminal nerve, which innervates the zygomatic muscles; whether this connection may be central or peripheral is not known. As a result of this abnormal nerve conduction, the patient’s trigeminal nerve innervates the biting muscles while simultaneously transmitting nerve impulses to the levator muscle causing the lid fissure to widen and the ptosis to then disappear. In patients with unilateral ptosis with superior rectus muscle insufficiency, the diagnosis of mandibular transient syndrome is made when the ptosis disappears when the patient is asked to open his or her mouth or perform a chewing motion. Regenerative misalignment syndrome is a disorder in which the extraocular muscles are innervated by nerve fibers that have regenerated in the wrong direction after actinic nerve paralysis and regenerative disturbances occur during the process of nerve repair. The majority of patients present with upper eyelid movements during eye movements. For example, the upper lid is raised when the internal rectus and upper and lower rectus muscles are contracted or when the eyeball is moved in the opposite direction of the paralyzed eye muscle. In addition, some patients have abnormal pupil size changes when they gaze in a particular direction. The diagnosis of regenerative misalignment syndrome is made in patients with ophthalmic nerve palsy who develop abnormal upper lid or pupil movements after paralysis. From the above, it is clear that mandibular transient syndrome, in which the upper lid is elevated in response to opening or chewing movements, may be the result of an abnormal connection between the motoneurotic nerve, which innervates the levator muscle, and the trigeminal nerve, which innervates the zygomatic muscles. Regenerative misalignment syndrome, in which the upper eyelid is elevated or the pupil moves abnormally with eye movements, is due to abnormal innervation of the motoneurotic nerve itself. Symptoms and signs are caused by an abnormal connection between the congenital trigeminal nerve and the central or terminal part of the oculomotor nerve, mostly unilaterally. When the mouth is opened and the jaw moves to the left or right, the lid fissure changes differently, with the upper lid lifted and the lid fissure opening wider than the healthy eye; when the mouth is closed, the upper lid returns to a drooping position. During chewing, the eyelid is constantly transient with the chewing motion of the jaw. Partial ocular muscle paralysis with internal strabismus. Diagnostic points 1. It is a less common form of congenital ptosis and co-movement of the jaw caused by an abnormal connection between the congenital trigeminal nerve and the central or terminal part of the motoneurotic nerve. 2. It is mostly unilateral. When the mouth is opened and the jaw moves to the left and right, the lid fissure changes differently, the upper lid is lifted and the lid fissure opens wide or even exceeds the healthy eye; when the mouth is closed the upper lid returns to its drooping position. 3. When chewing, the eyelid keeps transient with the chewing motion of the jaw. Partial ocular muscle paralysis with internal strabismus. Mild cases do not require treatment, severe cases can be operated. Treatment options Partial ophthalmoplegia with internal strabismus. No treatment is needed for mild cases, surgery is available for severe cases. Traditionally, the third branch of the trigeminal nerve is injected with ethanol or the trigeminal nerve root is cut and contused by craniotomy, which is difficult and dangerous. Segmental resection of the levator muscle with frontalis flap suspension can also be used with satisfactory results.