TIPS Clarifying lucent oval skull markings in children: craniolacunia, convolutional markings and copper- beaten skull SAndronikou MSSCh (WIts), FCRadDlag (SA), FRCR (London) eWelman MSChS E Kader MSChS Department of PatJdlatrtc RadIology, University of Caps Town and Institute of Child H88Ith, Red Cross War Memorial Children's Hosp/tal, Rondebosch, capa Town Corresponding author S Andronlkou Department of Paediatric Radiology, Red Cross War Memorial Children's Hospital, Cape Town, 7700 Tel: (021) 658-5422. Fax: (021) 658-5101. E-mail: docsaV®mweb.co.za Abstract Large oval Iucencies seen on the paediatric skull radiograph (SXR) may be normal or pathological. The radiologist, however, must be clear about which findings are pathological and the appropriate terminology when reporti ng on a paediatric SXR. By noting the clinical setting, the age of the patient and associated sku II abnormal ities, the appropriate terms can be used so that normal convol utional marki ngs can be distinguished from accentuated marki ngs of copper (silver)- 55 SAJOURNAL OF RADIOLOGY. February2001 beaten sku" in raised intracranial pressure (ICP) and the lacunae in patients with LUckenschadel accompanying spinal dysraphism. Keywords Craniolecurtie, convolutional markings" copper-beaten skull Introduction Large ovallucencies seen on the paediatric skull radiograph (SXR) may be normal or pathological. Dif- ferentiation of these does not usually affect management in current radiol- ogy practice, where an SXR is not commonly performed. The radiolo- gist, however, must be clear about which findings are pathological and what the appropriate terminology is when reporting on a paediatric SXR. By noting the clinical setting, the age of the patient and associated skull abnormalities, the appropriate terms can be used so that normal convolu- tional markings can be distinguished from accentuated markings of copper (silver)-beaten skull in raised intrac- ranial pressure (Iep) and the lacunae in patients with Liickenschadel ac- companying spinal dysraphism. Discussion Liickenschadelllacunar skull/ craniolacunia These numerous oval, lucent de- fects of the skull vault, varying in size, shape, number and degree, are due to a mesenchymal dysplasia (Figure la). They are found in association with myelomeningocoele, meningocoele and encephalocoele (Figure 1b). Only to page 56 Clarifying lucent oval skull rnarlciruzs in children from page 55 Figure la: Frontal SXR in a three-day-old child with spInal dysraphlsm demonstratIng ovallucencles surrounded by dense ridges. This is the mesenchy- mal dysplasia termed Uickenschade/. very rarely does this occur without dysraphism or cranioschisis.The proc- ess begins in utero but disappears at six months of age (whether or not a ventriculo-peritoneal shunt has been placed). Appearances vary from shal- low depressions on the inner vault of the skull to deep cavitations (lacunae) that extend to the outer skull surface. The lacunae do not correspond to the underlying convolutional pattern of the brain. Between the lacunae, lin- ear ridges of higher density bone are seen. The parietal and upper occipi- tal bones are commonly involved. The skull base is usually spared. As these features occur independently of raised ICP, the sutures and sella turcica are usually normal."? Convolutional markings/ digital impressions These are normal markings seen as areas of decreased density in the calvarium (Figure 2). They correspond closely to the location and configura tion of the under- lying cerebral convolutions. They- occur throughout the calvaria and those seen involving the floor of the anterior and middle fossae are most closely related to cer- ebral gyri. The rest of the lacunae on the vault are probably affected by pulsation of cerebrospinal fluid (CSF) in the sulci of a normal grow- ing brain, which causes impressions on the inner table. Even though con- volutional markings may be seen as early as eight months of age (in premature infants), they usually appear after the first year of life. They are most marked during the periods of rapid brain growth, which occur between 2-3 years and 5-7 years of age. They usually disap- pear by eight years of age.The sutures and sella turcica remain normal.P Figure 1b: A thoracic spine radiograph in the same child as in Figure la demon- strates the dorsal dysraphism (arrows) with widening of the spinal canal and numerous vertebral anomalies. ThIs patient had a clinically visible thoracic myelomeningocoele present at bIrth Hammer/ copper/silveri pewter-beaten skull 58 SAjOURNAL OF RADIOLOGY. February 2001 Figure 2: This six-year-old boy shows normal convolutional markings during the period of rapid brain growth. Note that the sutures (arrow) are visible and normal and that there are no changes involving the sella turcica (open arrow). Figure 3: This six-year-old boy shows accentuation of convolutional markings of a silver/copper- beaten skull The sagittal (not shown on this radiograph) and coronal sutures are completely fused, in keeping with craniosynostosis. The sellar demineralisation is in keeping with the resultant chronically raised ICP. This terminology is used when there are deep or accentuated convo- lutional markings in long-standing se- verely raised ICP (Figure 3). Such markings are not present at birth and do not occur before two months of age. Associated with this are features of raised ICP such as sutural diastasis and/or sellar demineralisation. The sutural changes are more common in younger children, while the sellar changes occur more commonly in older children. The copper-beaten to page 57 Clarifying lucent oval skull markings in children from page 56 skull is most marked when multiple sutures are fused, as occurs in primary craniosynostosis.ê-' Conclusion The differentiation of oval skull lucencies seen on children's SXRs can be undertaken by assessing the age of the child, clinical features and associ- ated SXR findings (Tables 1 and 2). Acknowledgements The authors would like to thank Jessica Bertelsmann for her help in the preparation of this article. References 1. Robertson RL, Ball WS Jr, Barnes PD. Skull and brain. In: Kirks DR, Griscom NT (eds). Practical paediatric imaging. 3rd ed. Philadelphia: Lippincott-Raven. 1998: 78- 91. 2. Silverman FN, Byrd SE, Fitz CR. The skull. In: Silverman FN, Kuhn JP (eds). Caffey's paediatric X-ray diagnosis: An integrated imaging approach. 9th ed. St. Louis: Mosby. 1993: 20-34. 3. Chasler CN. Atlas of roentgen anatomy of the newborn and infant skull. St. Louis: Warren H Green. 1972 59-64. Table 1: Differentiation of lucent oval skull markings based on the age of the child Present at birth but disappear by 6 months of age ! Luckenschadel Usually appear after 1st year of life and disappear by 8 ~arSOfage. ost marked between 2 and 7 years of age ! Normal convolutional markings Occur In later childhood and adolescence (usually after 10 years of age) ! Accentuated abnormal convolutional markings (copper-beaten skull) Table 2: Differentiation of lucent oval skull markings in children Associated with spinal dysraphism ! LOekenschadei S7 SA JOURNAL OF RADIOLOGY· February 2001 Normal sutures are easily visible and not prematurely closed. Normal pituitary fossa. No clinical features of raised Intracranial pressure. ! Normal convolutional markings Associated with craniosynostosis. Clinical and radiological features of raised intracranial pressure such as pituitary sella demlnerallsation and sometimes sutural diastasis ! Accentuated abnormal convolutional markings (copper-beaten skull)