Editor—Craniolacunia (“Lückenschädel”) describes rounded or finger-like defects of the inner table of the membranous portion of the skull that are surrounded by strips of normal bone.1 In most cases, craniolacunia is associated with spina bifida and a resulting myelo- or myelomeningocele. Additional associated anomalies include hydrocephalus, Arnold-Chiari malformation (congenital hindbrain hernia), and Klippel-Feil sequence (fusion of cervical vertebrae/hemivertebrae).2 The pathological mechanism resulting in craniolacunia is not known. Since depressions in the inner table of the calvarium are particularly deep in cases of oxycephaly, scaphocephaly, and brain tumour, increased intracranial pressure was invoked as an aetiological factor.1 Increased intracranial pressure, however, can give rise to impressiones digitatae (impressions of cerebral gyri) but does not in itself result in craniolacunia. Thus, craniolacunia has not been reported in any patient with FGFR associated autosomal dominant craniosynostosis. A more recent hypothesis assumes internal decompression and concomitant external compression of the calvarium as the cause of craniolacunia.2 Accordingly, an abnormal contact …