Ptosis weakness is often caused by lesions of the levator ani muscle itself, the neuromuscular junction, or the motoneuron innervating the levator ani muscle: the most common cause is myasthenia gravis, which is caused by lesions of the neuromuscular junction, leading to ptosis weakness. Ptosis weakness is characterized by fluctuating symptoms, light in the morning and heavy in the evening, which means that the symptoms are less severe in the morning and more severe in the evening; there is also a common condition called mitochondrial encephalomyopathy, in which a condition called chronic extraocular muscle paralysis is often the first symptom. This is due to skeletal muscle pathology that cannot tolerate fatigue; there is also a common type of mitochondrial encephalomyopathy, which includes a type of chronic progressive extraocular muscle paralysis, the first symptom of which is often ptosis; there is also a muscle disease represented by oculopharyngeal myotonic dystrophy, which also tends to lead to eyelid ptosis; and there are also a variety of other reasons for the ptosis of the motor eye nerve, such as Diabetes mellitus, aneurysms, non-specific inflammatory diseases, all of which can cause symptoms of ptosis.