What is the reason for the weakness of both legs? There are several reasons for sleepy legs: the first one is cerebrovascular disease, especially the bilateral cerebral hemisphere multiple lacunar cerebral infarcts, which can cause bilateral limbs, including bilateral lower limbs of the weakness, so the phenomenon of sleepy legs. The second reason is myasthenia gravis, myasthenia gravis can cause generalized skeletal muscle weakness, which is characterized by mild symptoms in the morning and more severe symptoms in the afternoon. The third cause is Guillain-Barre Syndrome (GBS), which causes symmetrical weakness in the limbs and can cause drowsiness in the legs. The fourth reason is the spinal cord disease, especially the early stage of myelitis can also cause the phenomenon of sleepiness in the legs, so the occurrence of sleepiness in the legs must go to the hospital for medical treatment.