Inferior herniation of the cerebellar tonsils is defined as a condition in which the cerebellar tonsils exceed the greater occipital foramen downward by more than 5 mm due to insufficient cranial cavity capacity. The answer is no. Simple subungual hernia, without any clinical symptoms, does not require surgical treatment. The indications for surgery include: 1. Severe lower herniation, with obvious brainstem symptoms or cerebellar symptoms. 2. The patient has a spinal cord cavity, and the cavity is gradually increasing in size on review. 3.The patient has a small spinal cord cavity, but there is obvious separation, segmental, and sensory impairment. 4. The lower herniation is accompanied by vertebral dentition instability and cricoaxial subluxation.