Nadir Bir Lokalizasyon: Oksipital Kemik Yerleşimli Anevrizmal Kemik Kistinin BT ve MR Görüntüleme Bulguları

Case Report / Olgu Sunumu ISSN: Eur J Health Sci 2015;1(1):36-38 A Rare Localization: CT and MR Imaging Findings of Aneurysmal Bone Cyst Located in Occipital Bone Nadir Bir Lokalizasyon: Oksipital Kemik Yerleşimli Anevrizmal Kemik Kistinin BT ve MR Görüntüleme Bulguları Derya Güçlü1, Fahri Halit Beşir2, Ramazan Büyükkaya2, Beşir Erdoğmuş2, Ömer Önbaş2 1 2 Duzce Ataturk Government Hospital, Department Of Radiology, Duzce, Turkey Duzce University, School Of Medicine, Department Of Radiology, Duzce, Turkey ABSTRACT Aneurysmal bone cyst is a benign lesion of the bone, that is usually seen in the metaphysis of long bones and vertebra and that is rare in the craniofacial region. In the computed tomography of a 67-year-old female patient, a multiloculated, encapsulated and heterogeneous lesion consistent with aneurysmal bone cyst was detected, that was 4.7 cm x 3.2 cm in diameter, expansive, causing significant erosion in the outer tabula of occipital bone and that appeared hypointense in T1 sequence, and hyperintense in T2 on magnetic resonance imaging. In the present study computed tomography and magnetic resonance imaging findings were discussed by reviewing literature data. Keywords: Aneurysmal bone cyst, Computed tomography, Magnetic resonance imaging, Occipital bone. ÖZET Anevrizmal kemik kisti, genellikle uzun kemiklerin metafizinde ve omurgada görülen, kraniofasyal bölgede ise nadir rastlanan benign bir kemik lezyonudur. Oksipital bölgede sert kitle ile başvuran 67 yaşındaki bir bayan hastanın yapılan bilgisayarlı tomografisinde oksipital kemikte 4,7*3,2 cm bıyutlu ekspansil özellikli, dış tabulada belirgin erozyona sebep olan ve manyetik rezonans görüntülemede T1 ağırlıklı görüntülerde hipointens, T2 ağırlıklı görüntülerde hiperintens sıvı-sıvı seviyelenmeleri gösteren, multiloküle, enkapsüle ve heterojen, anevrizmal kemik kisti ile uyumlu lezyon tespit edildi. Bu çalışmada ileri yaşta, radyolojik olarak oksipital kemik anevrizmal kemik kisti tanısı konulan olgunun bilgisayarlı tomografi ve manyetik rezonans görüntüleme bulguları literatür bilgileri gözden geçirilerek değerlendirilmiştir. Anahtar Kelimeler: Anevrizmal kemik kisti, Bilgisayarlı tomografi, Manyetik rezonans görüntüleme, Oksipital kemik. Correspondence / İletişim Derya Guclu, MD, Duzce Ataturk Government Hospital, Department Of Radiology, Duzce, Turkey E-mail: Received / Geliş Tarihi: 11.04.2015 - Accepted / Kabul Tarihi: 24.04.2015 Introduction Aneurysmal bone cysts (ABC) are expansive, lytic and non-neoplastic bone lesions that contain multiple blood-filled cystic cavities with thin walls (1). ABCs are usually located in the metaphysis of long bones and the vertebra (2). They are rare in the skull bones with a rate of 2-6% (3). ABCs that are usually observed in the second decade have no significant sexual predilection although they are more common in females (5). In the evaluation of ABC, the differential diagnosis of which from other osteolytic lesions is difficult preoperatively, radiologic imaging together with multiplanar cross sections is helpful for both preoperative diagnosis and surgery (3). In the present report we aimed to discuss computed tomography (CT) and magnetic resonance www.eurjhs.com (MR) imaging findings, in a case of advanced age who had an ABC in the occipital bone that was diagnosed radiologically and review literature data. Case Report A 67 year-old lady presented with headache and a swelling on the right side of the nuchal region. In the physical examination of the patient, who had no history of trauma, a firm and fixed mass without any fluctuation or crepitation was palpated, that had no local heat, tenderness or redness. In the cranial CT a expansive lesion with a size of 4.7 cm x 3.2 cm and that caused a significant erosion in the outer tabula (Figure 1a, b) was detected in the occipital bone. On MRI a multiloculated, encapsulated and heterogeneous lesion was ob- 36 Yusuf et al. served that appeared hypointense in T1-weighted images and hyperintense in T2-weighted images with fluid-fluid levels (Figure 2a, b, c). Figure 1. Cranial CT shows an expansive lesion in the right side of the occipital bone that caused a significant erosion in the outer tabula. Figure 2. On MRI, a multiloculated, encapsulated and heterogeneous lesion without any extension into intracranial structures was observed that caused expansion and erosion and appeared hypointense in T1-weighted images and hyperintense in T2-weighted images with fluid-fluid levels. The lesion had no extension to the intracranial structures. The diagnosis was made as ABC according to radiologic findings and follow-up was recommended to the patient who declined surgery. Discussion The term ‘Aneurysmal bone cyst’ was first used 1942 by Jaffe and Lichtenstein to define nonneoplastic lesions of the long bones (6, 7). For the www.eurjhs.com Case Report / Olgu Sunumu pathogenesis of ABC several theories were suggested. From these theories of posttraumatic reparation altered hemodynamic or the development secondary to compression of other bone lesions don’t explain all cases. Trauma could be a predisposing factor but it is unknown to which extend it is important (5). Macroscopically these lesions are composed of cavities divided by septa and filled with either blood or serum. Microscopically it contains numerous caverns without any endothelial lining. Hemosiderin containing macrophages and multinucleated osteoclastic giant cells are abounded in the septa. The defined diagnosis is made by histopathologic examination (8). ABCs can be primary or secondary. Primary ABCs constitute a group where previous arteriovenous malformations are considered to be the cause and these are usually encountered in children. On the other hand, secondary ABCs are associated with a degeneration of a cyst, tumor or a fibroosseous lesion (8). Imaging methods can make important contributions in the diagnosis ABC. In direct x-rays it can be observed that expanded osteolytic spaces are divided into trabecula and a soft tissue mass around the lesion can be identified (4). CT gives an idea about the anatomic details of bones. In MRI fluid-fluid levels, bleeding, a hypointense rim representing a fibrous capsule and a strong contrast enhancement can be detected. However fluid-fluid levels on MRI can also be observed in other bone lesions like giant cell tumor with a bleeding into its cystic component, chondroblastoma, telangiectatic osteosarcoma and malignant fibrous histiocytoma (3). Our case had fluid-fluid levels within the lesion that caused expansion and erosion. En bloc resection is a surgical treatment method and it is usually curative (3, 8). Preoperative embolization may be used to decrease the bleeding during surgery (9). In cases where complete resection is impossible radiotherapy is an alternative but with a high recurrence rate (3). In conclusion, ABCs are rarely located in the skull and it is also rare in advanced ages. The differen (...truncated)