Sinking bone flap due to overdrainage of a ventriculoperitoneal shunt. A case report and review of the literature.

The widespread use of decompressive craniectomy and subsequent cranioplasty has led to a better understanding of its complications. However, cases of a sunken bone flap have hardly ever been described. We present the eighth case reported up to date and perform a review of the literature of this sporadic complication. A 40-year-old Caucasian male suffered a traumatic brain injury that required a decompressive craniectomy. One month after initial trauma autologous cranioplasty was performed. A ventriculoperitoneal shunt was also placed. Neurological status progressively improved but his therapist noted cognitive status decline 8 months later. Follow-up computed tomography showed a progressive sinking bone flap. The patient underwent bone flap removal and a custom-made calcium phosphate-based implant was inserted, leading to symptoms resolution. Bone resorption has been described as the main cause of sinking bone flap following cranioplasty. This entity may manifest with symptoms of overdrainage in patients with cerebrospinal fluid shunt devices.