Fact-sheet: Paradoxical brain herniation - sinking sink flap syndrome


Updated on 04/30/2026 at 10:52 AM

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Definition

Syndrome of the trephined is a rare, late complication of craniectomy, characterized by new neurologic symptoms that worsen with the Valsalva maneuver and improve with replacement of the bone flap (cranioplasty) or with recumbent positioning

Clinical features

Occurs weeks to months after surgery

Neurologic deterioration not explained by other etiologies

CT

Concavity of the brain parenchyma beneath the craniectomy defect

Mass effect:

  • sulcal effacement,
  • mass effect on the underlying cortex,
  • midline shift,
  • subfalcine herniation

Management

Treatment options:

  • Recumbent or Trendelenburg positioning
  • Treatment of the underlying cause: overdrainage of cerebrospinal fluid, dural breach after lumbar puncture
  • Cranioplasty