Unexpected complications immediately after cranioplasty

CASE: An 84‐year‐old man with subarachnoid hemorrhage underwent craniotomy and clipping with external decompression. Perfusion magnetic resonance imaging showed subclinical sinking skin flap syndrome, and he underwent cranioplasty on postoperative day 58. No problems occurred during the operation, but cerebral edema and hemorrhage were recognized on immediate postoperative computed tomography. Edema continued to progress, but edema and bleeding eventually improved without additional surgery. OUTCOME: Neurological symptoms improved to presurgical baseline and stabilized. CONCLUSION: Causes of cerebral edema and hemorrhage immediately after cranioplasty include reperfusion, reduction of automatic adjustment function, sinking skin flap syndrome, negative pressure due to s.c. drain, venous stasis, vascular damage following restoration of midline shift, and allergic reaction. Although cranioplasty itself is a relatively minor surgery, the fatality rate for this complication is high. Most complications are due to infection, convulsions, or epidural hematoma, but brain edema and hemorrhage also occur. It is necessary to elucidate the etiology before corrective surgery.