External cranioplasty for the syndrome of the trephined – Case report

•Decompressive craniectomy controls intracranial hypertension secondary due to brain swelling.•The syndrome of the trephined is a complication after decompressive craniectomy.•The treatment is cranioplasty, however, but some circumstances prevent definitive therapy.•The making of a plaster helmet has proved to be an effective temporary treatment.