Any surgery that involves the nervous system (brain or spinal cord or peripheral nerves) WordNet 3.0 & Open English WordNet

Neurosurgery or neurological surgery, known in common parlance as brain surgery, is the medical specialty concerned with the surgical treatment of disorders which affect any portion of the nervous system including the brain, spinal cord and peripheral nervous system. Wikipedia

Surgery performed on the nervous system; medical specialty concerning disorders which affect any portion of the nervous system Wikidata

The surgical discipline focused on treating those central and peripheral nervous system diseases. Wiktionary