What is one reason that brain or spinal injuries cannot often be repaired?

One reason that brain or spinal injuries cannot often be repaired is that the specialized cells in these areas do not regenerate. Unlike many other tissues in the body, the neurons in the brain and spinal cord do not divide and reproduce, so if they are damaged or destroyed, they cannot be easily replaced. This makes it difficult for the body to repair itself after an injury, and it also explains why brain and spinal injuries can lead to permanent impairments and disabilities.