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The sinking bone syndrome?

Bone resorption is a known complication of cranioplasty after decompressive craniectomy (DC). A peculiar group of insidious, progressive, invalidating neurological symptoms was observed in patients presenting with incomplete resorption and abnormal mobility of the re-implanted bone. Such symptoms were similar, but with time more severe, to those encountered in the sinking flap syndrome. Are we facing a sort of Sinking Bone Syndrome? We accurately analyze these cases and review the literature. Over a 7-years period, 312 DCs were performed at our Institution. In 7 patients, headache, vertigo, gait ataxia, confusion, blurred speech, short-term memory impairment, hemiparesis, sudden loss of consciousness, and third cranial nerve palsy were observed in a time period ranging from 18 months to 5 years after cranioplasty. Clinical and neuroradiological examinations were performed to disclose the possible etiopathogenesis of this condition. Collected data showed partial resorption of the repositioned bone and its unnatural inward movements during postural changes. Bone movements were interpreted as the major cause of the symptoms. A new cranioplasty was then performed in every case, using porous hydroxyapatite in 6 patients and polyetherketone implant in the other. Full resolution of symptoms was always obtained 3 to 20 days after the second surgery. No further complications were reported. We believe that long-term follow up in patients operated on by cranioplasty after DC will be needed regularly for years after skull reconstruction and that newly appearing symptoms should never go underestimated or simply interpreted as a long-term consequence of previous brain damage.