Imaging of the post-operative cranium.

Imaging plays an essential role in the evaluation of patients after cranial surgery. It is important to be familiar with the normal anatomy of the cranium; the indications for different surgical techniques such as burr holes, craniotomy, craniectomy, and cranioplasty; their normal postoperative appearances; and complications such as tension pneumocephalus, infection, abscess, empyema, hemorrhage, hematoma, herniation, hygroma, and trephine syndrome. Postoperative infection and hemorrhage are common to all neurosurgical procedures, where-as other complications are peculiar to certain procedures (eg, drill "plunging" during burr hole creation and sinking skin flap after craniec-tomy). Recognizing life-threatening complications such as tension pneumocephalus and paradoxical herniation, which require urgent intervention, is important for a better clinical outcome. Computed tomography is fast, cost effective, and easily accessible for first-line imaging. Magnetic resonance imaging has higher sensitivity for detecting postoperative infection and ischemia, but diffusion-weighted imaging may be less reliable for detecting postoperative infections.