Since neurosurgery is a specialty focused on a physiological system rather than a specific anatomical region, neurosurgeons treat diseases that affect all types of patients in various parts of their bodies. For example, a typical neurosurgeon not only operates on the brain and spinal cord but may also perform procedures on the skull, face, neck, spine, arms, and legs. Neurosurgeons care for some of the youngest patients in the hospital, such as a premature infant with a congenital malformation, as well as young and elderly adults suffering from trauma, tumors, infections, vascular anomalies, or degenerative disorders. The level of care provided by neurosurgeons is similarly broad—some patients do not require an operation at all (observing a patient after mild head injury), some undergo outpatient surgery (carpal tunnel release or lumbar microdiscectomy), while others may be very unstable and critically ill for days and weeks during their treatment (ruptured intracranial aneurysm, traumatic brain injury). Therefore, neurosurgery is a very diverse field with varying and unique challenges.