At each level in the spine, a nerve emerges which goes out to supply nerve impulses to various body regions, including skin, muscle and organs. The area of the nerve as it emerges is called the nerve root. Each nerve root is surrounded by a little tunnel of connective tissue called the nerve root sleeve. Inside the nerve root sleeve is continuous with the epidural space of the spine, so an injection, which places medicines inside this tunnel, is effectively a type of epidural injection. A nerve root sleeve injection places a small amount of local anaesthetic and cortisone-type medication into the nerve root sleeve.