Bone flap replacement after a decompressive craniectomy is a low complexity procedure, but with complications that can negatively impact the patient\'s outcome. A better knowledge of the risk factors for these complications could reduce their incidence.
A retrospective review of a series of 50 patients who underwent bone replacement after decompressive craniectomy at a tertiary center over a 10-year period was performed. Those clinical variables related to complications after replacement were recorded and their risk factors were analyzed.
A total of 18 patients (36%) presented complications after bone flap replacement, of which 10 (55.5%) required a new surgery for their treatment. Most of the replacements (95%) were performed in the first 90 days after the craniectomy, with a tendency to present more complications compared to the subsequent period (37.8% vs 20%, p > 0.05). The most frequent complication was subdural hygroma, which appeared later than infection, the second most frequent complication. The need for ventricular drainage or tracheostomy and the mean time on mechanical ventilation, ICU admission, or waiting until bone replacement were greater in patients who presented post-replacement complications. Previous infections outside the nervous system or the surgical wound was the only risk factor for post-bone flap replacement complications (p = 0.031).
Postoperative complications were recorded in more than a third of the patients who underwent cranial bone flap replacement, and at least half of them required a new surgery. A specific protocol aimed at controlling previous infections could reduce the risk of complications and help establish the optimal time for cranial bone flap replacement.

BACKGROUND: The decompressive hemicraniectomy (DCH) after malignant middle cerebral artery infarction in children is a rare procedure, and the indication is discussed as being controversial. Etiological Moyamoya disease has some additional challenges concerning the therapeutic strategy that have not mentioned in the recent literature, as it is dependent on special pathophysiology.
METHODS: We report a case of a four-year-old patient with a decompressive hemicraniectomy after malignant middle cerebral artery infarction on the right hemisphere based on a Moyamoya syndrome with proximal MCA occlusions on both sides. After the decompression there was a good restitution of the hemiparesis, aphasia, and consciousness loss on admission. The bone flap replacement is usually done after three month in our department to ensure brain swelling has subsided. In this patient the cranioplasty was not arranged because of the development of collateral vessels to the right motor region through the craniotomy defect, to protect the supply of the eloquent cortex.
CONCLUSIONS: We conclude that the indication of DCH and postoperative treatment should be discussed individually, especially when neovascularisation developments can occur like in Moyamoya disease. An important point is the right timing for bone flap replacement, which should be directly after cerebral edema has subsided prior to the evolution of collaterals through the craniotomy defect. Additionally, leaving the opportunity for neovascularization through smaller defects has to be taken into account.