Complex sentence: She became Chief of Neurosurgery at the Children's Hospital of Michigan in 1987 and held the position until her retirement in 2001, specializing in congenital spinal abnormalities, hydrocephalus, trauma and brain tumors.
Split into simpler sentences: She became Chief of Neurosurgery at the Children's Hospital of Michigan in 1987 and held the position until her retirement in 2001. During her time as Chief, she specialized in congenital spinal abnormalities, hydrocephalus, trauma and brain tumors.