Asymmetry of Bell’s phenomenon in both eyes is one of the symptoms of monocular double supination palsy. Monocular double supination palsy is manifested by asymmetric Bell phenomenon in both eyes, and the affected eye tends to be worse or disappear. 1, the pathogenesis of monocular double supination palsy has congenital and acquired, the real cause is not very clear. 2, the pathogenesis of some people believe that it may be part of the residual paralysis in the recovery process of the motoneural nerve paralysis. In terms of congenital, according to the anatomy of the motoneuron, the nucleus of the motoneuron is, from top to bottom, the nucleus of the levator aponeurosis, the nucleus of the superior rectus and the nucleus of the inferior oblique, with the nucleus of the medial rectus and inferior rectus. The nucleus accumbens and the nucleus accumbens may be damaged during maternal pregnancy. In acquired cases, trauma, brain inflammation, tumors, and other factors may lead to actinic nerve palsy. In both congenital and acquired cases, there is a certain order of recovery from motoneural nerve palsy, with the superior levator muscle recovering the earliest and fastest, followed by the medial rectus, inferior rectus, and pupillary sphincter muscles, and the superior rectus and inferior oblique muscles recovering the latest or not, thus showing the characteristic double supination muscle palsy in one eye. Because the superior rectus and levator aponeurosis are differentiated from 1 muscle, although the function of the levator aponeurosis has recovered, it exhibits a pseudohypoplasia state because of the pulling action of the underfunctioning superior rectus muscle. Mixed and true ptosis may be associated with incomplete or unrecovered function of the nerves innervating the levator muscle. The pathological changes are mainly located in the anterior horn of the spinal cord, where the motor cells are significantly reduced and degenerated, with residual nerve cells showing consolidation and nucleolysis, thinning of the axons of the anterior spinal cord roots, and swelling of the peripheral cells of the axons. Brainstem motor nerve nucleus degeneration, with facial, vagus, and hypoglossal nerves being the most common. The muscle pathology is described in the following section of the ancillary examinations.