Case key points:

• the rare and potentially fatal complication of decompressive hemicraniectomy, paradoxical brain herniation, requires early recognition and urgent treatment

• growing indications for decompressive craniectomy requires the radiologist to be cognizant of the clinical characteristics and imaging appearances of paradoxical brain herniation

• symptoms and imaging findings that may raise concern/constitute the syndrome are 

  • acute postoperative deterioration after hemicraniectomy with or without temporal association with external ventricular drainage or lumbar puncture

  • sinking skin flap

  • marked concavity at the craniotomy site accompanied by subfalcine and/or transtentorial herniation

What is more, this case illustrates the time course of space-occupying MCA infarction including hemorrhagic transformation, Wallerian degeneration, decompressive surgery complicated by above mentioned and subgaleal abscess and is a textbook example of the controversy regarding optimal timing of cranioplasty.