Aneurysmal bone cyst within fibrous dysplasia of the anterior skull base: continued intracranial extension after endoscopic resections requiring craniofacial approach with free tissue transfer reconstruction

Abstract

Fibrous dysplasia (FD) is a rare pathology that represents 2.5 % of all bone tumors and 7 % of benign bone tumors [1]. It is most commonly found in female patients under the age of 30 [2]. It is an idiopathic disorder and is a malformation characterized by an intramedullary cavity proliferation of fibrous tissue with woven bony trabeculae and spindleshaped fibroblasts [3]. The most affected craniofacial bones are maxilla, mandible, frontal, sphenoid, and temporal bones [4]. Aneurysmal bone cysts (ABCs) are non-neoplastic lesions with benign pathology which can occur within FD. These tumors have no propensity to metastasize, but become symptomatic as a result of their tendency to be locally destructive [5]. ABCs were originally described by Jaffe and Lichenstein in 1942 [6]. The name ABC is a misnomer as it is neither an aneurysm nor a true cyst. Seventy-five percent of the patients having ABCs are under 20 years of age. They are most commonly found in long bones and the spinal column with skull involvement being rare [7]. ABCs normally present as primary osseous lesions; however, in 30 % of cases, they occur secondary to other bone lesions. The association of ABCs with a FD is a known but rare entity. Recently, the authors have cared for a child with aggressive FD of the anterior skull base with secondary ABC refractory to multiple endoscopic endonasal resections. The definitive treatment for the intracranial extension was an open craniotomy with extensive skull base reconstruction using a myofascial free flap from the anterolateral thigh.