What is the difference between a craniotomy for subdural hematoma ? vs decompressive craniectomy for subdural hermatoma ? what causes a craniotomy for subdural hematoma?

Craniotomy is the surgical technique for most patients with acute subdural hematoma who undergo hematoma evacuation. Craniectomy may be used for patients with acute subdural hematoma who also have cerebral edema or brain herniation to prevent further morbidity from brain herniation.

These are terms for surgical intervention, and the key here is the need to save lives and prevent brain tissue destruction due to the risk of progressive bleeding acting as a pressure mass. Although some cases allow conservative non-invasive management, quite often the need for decompression is paramount.