Aneurysmal Bone Cyst of the Temporal Bone: Case Report Hakan Tuna, M.D., Ayse Karatas, M.D., Erdal R. Yilmaz, M.D., Banu Yagmurlu, M.D., and Selim Erekul, M.D. Department of Neurosurgery, Ankara University School of Medicine, Ankara, Turkey Tuna H, Karatas A, Yilmaz ER, Yagmurlu Y, Erekul S. Aneurysmal bone cyst of the temporal bone: case report. Surg Neurol 2003; 60:571– 4. BACKGROUND Aneurysmal bone cysts (ABCs) are uncommon lesions of the temporal bone and their occurrence in the calvarium is rare. CASE DESCRIPTION A case of a right temporal ABC is reported in a 14-year-old boy who presented swelling of the right temporal region. Magnetic resonance imaging showed a destructive and expansile bone lesion on the right anterior temporal and orbital bone. The lesion was removed in total by the right temporal craniotomy and orbitozygomatic osteotomy. ABC was diagnosed in the pathologic examination. The patient had good recovery during the postoperative course. CONCLUSIONS This report presents the diagnosis and imaging of an ABC in the temporal bone. This localization is very rare for ABC. Total excision, if feasible, is the ideal treatment. © 2003 Elsevier Inc. All rights reserved. KEY WORDS Aneursymal bone cyst, temporal bone. A neurysmal bone cysts (ABCs) are uncommon lesions of the bone and are benign and non- neoplastic in nature. They most commonly develop in the metaphysis of long bones. Their occurrence in the calvaria is rare [1,2,4,18]. Reports of skull bone involvement in ABC mention occipital, frontal, and temporal bones as common seats of origin. While the histologic features are well known, the pathophysiology of this condition is unclear. ABCs are expansile, lytic bony lesions consisting of mul- tiple thin-walled, blood-containing, nonendothelial- ized cystic cavities. ABC was first described as sep- arate from the group of giant cell tumors by Jaffe and Lichtenstein in 1942 [13] and has been recog- nized as a distinct bone pathology. The lesion was determined to originate as a vascular disturbance giving the characteristic radiologic picture of a “blow-out” of bone. Case Report The patient was a 14-year-old boy admitted to our clinic with complaints of a swelling in the right temporal region. The lesion, which the patient him- self noticed, had been increasing in size over the previous month. His medical history was unremark- able, and there was no history of trauma. EXAMINATION He had a marked, immobilized, hard swelling in the right temporal region. It was painless, afebrile, and nonpulsatile. His neurologic examination was en- tirely normal, with no symptoms of increased intra- cranial pressure and normal eye mobility. Routine laboratory investigations, including se- rum calcium, phosphorus, and alkaline phospha- tase, were normal. Plain X-ray skull films were entirely normal. Mag- netic resonance imaging (MRI) demonstrated a large (3  4  4.5 cm) expansile and destructive mass located in the infratemporal fossa region, orig- inating from the greater wing of the sphenoid bone adjacent to the lateral wall of the orbit and expand- ing into the intraocular space. The hemorrhagic component seen in hyperintense signal with fluid- fluid levels was demonstrated on T1-weighted im- ages (Figure 1). The hyperintense hemorrhagic component with fluid-fluid levels and the isointense character of the solid part were demonstrated on T2-weighted images (Figure 2). The solid part of the mass was seen enhancing heterogenously on post- contrast images (Figure 3). OPERATION The lesion was exposed by right temporal craniot- omy and orbito-zygomatic osteotomy approach. Af- Address reprint requests to: Dr. Ayse Karatas, Ankara U ¨ niversitesi Tip Faku¨ltesi, Ibni Sina Hastanesi Beyin Cerrahisi Klinigi, 06100 Samanpazari, Ankara, Turkey. Received August 7, 2002; accepted January 8, 2003. © 2003 Elsevier Inc. All rights reserved. 0090-3019/03/$–see front matter 360 Park Avenue South, New York, NY 10010 –1710 doi:10.1016/S0090-3019(03)00241-6