Sinking flap syndrome revisited: the who, when and why.

The sinking flap syndrome (SFS) is one of the complications of decompressive craniectomy (DC). Although frequently presenting with aspecific symptoms, that may be underestimated, it can lead to severe and progressive neurological deterioration and, if left untreated, even to death. We report our experience in a consecutive series of 43 patients diagnosed with SFS and propose a classification based on the possible etiopathogenetic mechanisms. In 10 years' time, 43 patients presenting with severely introflexed decompressive skin flaps plus radiological and clinical evidence of SFS were identified. We analysed potential factors involved in SFS development (demographics, time from decompression to deterioration, type, size and cause leading to DC, timing of cranioplasty, CSF dynamics disturbances, clinical presentation). Based on the collected data, we elaborated a classification system identifying 3 main SFS subtypes: (1) primary or atrophic, (2) secondary or hydrocephalic and (3) mixed. Very large DC, extensive brain damage, medial craniectomy border distance from the midline < 2 cm, re-surgery for craniectomy widening and CSF circulation derangements were found to be statistically associated with SFS. Cranioplasty led to permanent neurological improvement in 37 cases. In our series, SFS incidence was 16%, significantly larger than what is reported in the literature. Its management was more complex in patients affected by CSF circulation disturbances (especially when needing the removal of a contralateral infected cranioplasty or a resorbed bone flap). Although cranioplasty was always the winning solution, its appropriate timing was strategical and, if needed, we performed it even in an emergency, to ensure patient's improvement.