Lack of sensation below the buttocks belongs to sensory disorder, and the main reasons are related to sciatic nerve injury, spinal cord injury, brain injury and so on. 1. Sciatic nerve injury: when there is sciatic nerve injury, it will produce motor and sensory dysfunction in the area innervated by the sciatic nerve, so it will form the manifestation of lack of sensation below the buttocks, and may be accompanied by the phenomenon of muscle contraction weakness. 2. Spinal cord injury: when there is spinal cord injury, it is easy to cause paraplegia symptoms, such as bilateral loss of motor and sensory functions of the lower limbs, resulting in the lack of sensation below the buttocks. 3. Brain injury: some patients with brain injury are prone to affect the motor and sensory functions of the limbs, thus resulting in the phenomenon of having no sensation below the buttocks, which is usually accompanied by motor control disorder of the limbs. The persistence of the lack of sensation below the buttocks needs to be identified as soon as possible, according to the severity of the disease, under the guidance of specialized physicians targeted treatment. In daily life, pay attention to care to prevent the phenomenon of bilateral lower limb burns or abrasions.