Revisiting Galen: enduring contributions from ancient times towards modern neurosurgery.

This historical vignette aims to reflect on the life of Claudius Galen and critically discuss his contributions towards modern neurosurgical practice; specifically, neuroanatomy, neurophysiology, and cranial trepanation. Born in 129 AD in the Greek city of Pergamon, Galen dedicated his early life to the study of medicine and established himself as one of the foremost physicians of the time. Through vivisections of Barbary apes, he was one of the first to provide a detailed description of cranial nerves, the ventricular system of the brain, and various deep brain structures. He made an important distinction between motor and sensory nerves and mapped out the fundamental arrangement of neuronal fibers within the spinal cord. However, his fundamental understanding of neurophysiology, as well as cerebral blood circulation, was largely flawed as it was based on speculation of inter-species comparative anatomy. On the technical side, he made a modest contribution to the practice of cranial trepanation and his writings helped establish the technique as an essential component of a surgeon's armamentarium. His work in the fields relevant to modern neurosurgery, although imperfect with the benefit of hindsight, laid the important foundation for much of the progress of neurosurgical practice in the Renaissance and beyond.