Neurosurgery is the medical specialty concerned with the prevention, diagnosis, treatment, and rehabilitation of disorders which affect any portion of the nervous system including the brain

Human brain

The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...

, spine, spinal cord

Spinal cord

The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...

, peripheral nerves

Peripheral nervous system

The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...

, and extra-cranial cerebrovascular system.
In the United States, a neurosurgeon must generally complete four years of college, four years of medical school, a year-long internship (PGY-1) that is usually affiliated with their residency program, and five to six years of neurosurgery residency

Residency (medicine)

Residency is a stage of graduate medical training. A resident physician or resident is a person who has received a medical degree , Podiatric degree , Dental Degree and who practices...

 (PGY-2-7).