Overt Cerebrospinal Fluid Drainage Is Not a Sine Qua Non for Paradoxical Herniation After Decompressive Craniectomy

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Paradoxical transtentorial herniation is a rare but well-documented complication of cerebrospinal fluid (CSF) drainage in patients with large decompressive craniectomies. However, brain sagging in the absence of CSF hypovolemia has not been previously reported. A 30-year-old woman suffered massive intracerebral hemorrhage from a small residual left frontal arteriovenous malformation 1 year following endovascular embolization and stereotactic radiosurgery. The patient initially presented in coma with left mydriasis and decorticate posturing and underwent emergent decompressive craniectomy, evacuation of the hematoma, and insertion of an intracranial pressure (ICP) monitor. Postoperatively, despite a depressed skin flap and low ICP readings, she continued to deteriorate neurologically, and CT revealed increasing midline shift, transtentorial herniation, and brainstem compression. INTERVENTION OR TECHNIQUE: Although there was no history of CSF drainage, the diagnosis of brain sag was suspected, because herniation seemed to occur in the setting of intracranial hypotension. The patient was placed in a 15 degrees Trendelenburg position and improved dramatically within hours. A few days later, she was fully awake and had purposeful movements with her left side, although she had persistent aphasia and right hemiplegia. Although rare, paradoxical herniation in the setting of a large craniectomy defect may occur in the absence of CSF drainage. This entity should be suspected whenever transtentorial herniation occurs in conjunction with direct or indirect signs of intracranial hypotension. Placing the patient in the Trendelenburg position should be attempted, because this simple maneuver may turn out to be life-saving.