Decompressive craniectomy is frequently performed in cases of resistant intracranial hypertension secondary to several neurological conditions and is commonly followed by cranioplasty. Complications, such as infection and hematomas after cranioplasty occur in roughly about a third of cases. Massive brain swelling after cranioplasty (MSBC) is a rare and potentially fatal complication of an uneventful cranioplasty that has recently been elucidated. Preoperative sinking skin flap (SSF) and intracranial hypotension were factors associated with the development of MSBC after cranioplasty. Data suggests that pathologic changes are triggered immediately following the procedure, especially an acute increase in intracranial pressure.