Acta Oto-Laryngologica, 2005; 125: 1126 /1129
CASE REPORT
Monostotic fibrous dysplasia of temporal bone: Report of two cases and review of its characteristics
JAE-JUN SONG, HAK-HYUN JUNG, HEUNG-MAN LEE & SOON-JAE HWANG Department of Otorhinolaryngology */Head and Neck Surgery, Korea University College of Medicine, Seoul, South Korea
Abstract Fibrous dysplasia is a bone disorder of unknown origin characterized by slow, progressive replacement of bone by abnormal proliferative isomorphic fibrous tissue. The disease was first described by McCune and Bruch in 1937. Craniofacial involvement is found in only 10% of cases of the monostotic variety, while temporal bone involvement is rare. We report herein two cases of monostotic fibrous dysplasia involving temporal bone and briefly review the clinical implications and management of the disease.
Keywords: Fibrous dysplasia, temporal bone
Introduction Fibrous dysplasia is a developmental disorder caused by abnormal proliferation and maturation of fibroblasts resulting in replacement of mature bone by structurally weak, immature, woven bone. Craniofacial fibrous dysplasia represents :/3% of all bone tumors and 7% of benign tumors [1]. However, monostotic fibrous dysplasia confined to temporal bone is very rare, with fewer than 60 cases having been reported in the English language literature [2]. We report herein two cases of monostotic fibrous dysplasia involving temporal bone and briefly review the clinical implications and management of the disease.
Case reports Case 1 A 34-year-old male presented with a 5-year history of right temporal headache. Examination revealed a mild swelling in the right temporal region. The external auditory canal and tympanic membrane were normal. Audiologic tests, including pure-tone and impedance audiometry, were normal and other laboratory investigations were all normal. A CT scan
revealed predominant involvement of the squamous and mastoid portions of temporal bone (Figure 1). There was partial invasion of the petrous ridge, but the anterior and posterior fossae remained intact. The patient was satisfied with his facial contour but the lesion was biopsied for pathologic confirmation and confirmed fibrous dysplasia. Case 2 A 20-year-old female presented with a 10-year history of progressive swelling of the right temporal area and hearing loss. In the previous year there had been rapid increases in the size of the swelling and in hearing loss. Physical examination revealed a bony tender swelling in the right temporal region. There were no changes in the overlying skin, which was easily movable over the swelling. Otoscopic examination revealed a narrow right external auditory canal with skin inflammation. A normal-looking tympanic membrane could partly be seen. Puretone audiometry demonstrated a 30-dB air/bone gap. Impedance audiometry was normal and a neurological examination was unremarkable. Laboratory investigations were normal. Plain radiographs revealed expansion and thickening of
Correspondence: Soon-Jae Hwang, MD, Department of Otorhinolaryngology */Head and Neck Surgery, Korea University Guro Hospital, 80 Guro-dong, Guro-gu, Seoul 152-050, South Korea. Tel: /82 2 818 6157. Fax: /82 2 868 0475. E-mail:
[email protected]
(Received 17 December 2004; accepted 10 February 2005) ISSN 0001-6489 print/ISSN 1651-2551 online # 2005 Taylor & Francis DOI: 10.1080/00016480510035430
Monostotic fibrous dysplasia of temporal bone
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Figure 1. CT findings for Case 1. (A) Axial temporal bone CT image showing the diffuse ground-glass appearance of the right temporal mastoid, with obliteration of air cells. Note bony expansion without cortical disruption and the fact that the ipsilateral middle ear cavity, bony labyrinth, internal auditory canal and facial nerve canal are relatively spared. (B) Coronal temporal bone CT image showing right temporal mastoid, which has homogenously increased in density.
temporal bone, with some sclerosis of bony margins. A CT scan revealed involvement of the right temporal bone and intrusion into the middle cranial fossa (Figure 2). Osteitis was accompanied by necrotic changes in the squamous portion of temporal bone. The patient was scheduled for surgery, primarily to remove the osteitic lesion but also to correct the disfigurement. After reflecting the skin flap, the intact periosteum was also reflected. The osteitic lesion and accompanying necrotic region were removed using a drill and curette. Excess woven bone tissue was removed to give a cosmetically acceptable result. The postoperative period was
uneventful. Histopathological examination confirmed fibrous dysplasia. Discussion Fibrous dysplasia is characterized by slow, progressive replacement of bone by an abnormal proliferative isomorphic fibrous tissue, intermixed with poorly formed and irregularly arranged trabeculae of woven bone. In 1937, McCune and Bruch [3] first suggested that, among the abnormalities of bone formation, this disorder should be recognized as a distinct
Figure 2. CT findings for Case 2. (A, B) Axial and coronal temporal bone CT images showing the extensive ground-glass appearance of the right temporal and sphenoid bones, with expansion. Multilocular radiolucent lesions are also intermixed with multiple cortical perforation. The ipsilateral internal auditory canal, external auditory canal and facial nerve canal are obliterated by the diffuse ground-glass appearance, with the exception of the intact otic capsule.
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clinical entity. Lichtenstein [4] introduced the term fibrous dysplasia. This entity reportedly constitutes 2.5% of all osseous and 7% of all benign osseous neoplasms [5]. The male:female ratio is 2:1. A race predilection has been observed, with Caucasians comprising 80% of all cases, African /Americans 2% and Asians 1% [1]. The precise etiology of fibrous dysplasia is currently unknown. As a cause of the bony abnormalities, abnormal differentiation of mesenchyme was proposed by Lichtenstein and Jaffe [4]. Reed [6] proposed a theory that includes arrest of bone growth at an immature woven stage and a disturbance of postnatal cancellous bone maintenance. It has also been proposed [7] that fibrous dysplasia may be associated with increased levels of steroid hormone receptors (receptors of estrogens or progesterone). Fibrous dysplasia is divided into three subtypes: monostotic, polystotic and McCune /Albright syndrome. Monostotic lesions are commonest (70%) and usually involve the ribs and femurs. They grow slowly and usually appear to have stopped growing after puberty. Because many patients are asymptomatic and are often diagnosed incidentally, the incidence of the monostotic form is considered to be highest. Polystotic disease frequently becomes evident late in childhood and accompanies more severe skeletal and craniofacial involvement [7]. Polystotic disease commonly affects the sphenoid, frontal, maxillary and ethmoid bones. Occipital and temporal bone involvement is rare [8]. The most severe form of the disorder, McCune / Albright syndrome, is more commonly found in females and is associated with short stature due to premature closure of the epiphyses and with endocrine abnormalities and pigmented cutaneous lesions [9]. Many endocrine abnormalities have been reported; hyperthyroidism is the commonest, being encountered in 5% of patients with this syndrome [10]. Progressive conductive hearing loss caused by occlusion of the Eustachian tube or external auditory canal are the commonest symptoms of fibrous dysplasia involving temporal bone [8]. The usual presentation is progressive hearing loss and an expanding mass over the post-auricular region. Deafness is commonly conductive as a result of external auditory canal obliteration, although sensorineural deafness has also been reported [11]. Sensorineural hearing loss occurs in 14 /17% of patients. Facial nerve involvement is seen in 10% of patients with fibrous dysplasia of the temporal bone and cholesteatoma occurs in almost 40% [12]. Other symptoms include tinnitus, dizziness, pain, trismus
and neurologic signs relating to the involvement of the middle or posterior cranial fossae [1,8]. Three classical radiologic findings of fibrous dysplasia have been described [9]: pagetoid, sclerotic and myxoid. The pagetoid, or ground-glass pattern, is the commonest. The sclerotic pattern is uniformly dense. The cystic pattern is characterized by spherical or ovoid lucidity surrounded by a dense bony shell [2]. Distinguishing features of fibrous dysplasia on CT include a ground-glass appearance, involvement of the paranasal sinuses, thickened cranial cortices, nasal cavity involvement, the presence of a soft tissue mass, maxillary involvement and the presence of cystic changes [13]. The differential diagnosis of fibrous dysplasia includes meningioma, aneurismal bone cyst, unicameral cyst, ossifying or non-ossifying fibroma, Paget’s disease, osteochondroma, giant cell tumor, eosinophilic granuloma, exostosis, osteoma and sarcomatous neoplasm [2]. There is no specific medical treatment for fibrous dysplasia. Asymptomatic monostotic lesions can be monitored regularly without any intervention. Surgical management is justified if the lesions become symptomatic. Indications for surgery include bony encroachment of the external auditory canal, recurrent infection and secondary canal cholesteatoma [11]. The surgeon should be aware that surgery of the dysplastic temporal bone can be hazardous because landmarks are often obliterated and intraoperatave bleeding can be vigorous. Radiation therapy should be avoided because of the high incidence of malignant transformation [14]. Spontaneous transformation to malignancy in fibrous dysplasia of the temporal bone is extremely rare [8]. Malignant transformation is indicated by pain, aggressive growth and elevation of the level of serum alkaline phosphatase [15].
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Monostotic fibrous dysplasia of temporal bone [6] Reed RJ. Fibrous dysplasia of bone. A review of 25 cases. Arch Pathol 1963;75:480 /95. [7] Albin J, Wu R. Abnormal hypothalamic-pituitary function in polyostotic fibrous dysplasia. Clin Endocrinol (Oxf) 1981; 14:435 /43. [8] Lambert PR, Brackmann DE. Fibrous dysplasia of the temporal bone: the use of computerized tomography. Otolaryngol Head Neck Surg 1984;92:461 /7. [9] Nager GT, Holliday MJ. Fibrous dysplasia of the temporal bone. Update with case reports. Ann Otol Rhinol Laryngol 1984;93:630 /3. [10] Morrissey DD, Talbot JM, Schleuning AJ, 2nd. Fibrous dysplasia of the temporal bone: reversal of sensorineural hearing loss after decompression of the internal auditory canal. Laryngoscope 1997;107:1336 /40.
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[11] Chee GH, Chen JM. Fibrous dysplasia of the temporal bone. Otol Neurotol 2002;23:405 /6. [12] Megerian CA, Sofferman RA, McKenna MJ, Eavey RD, Nadol JB, Jr. Fibrous dysplasia of the temporal bone: ten new cases demonstrating the spectrum of otologic sequelae. Am J Otol 1995;16:408 /19. [13] Tehranzadeh J, Fung Y, Donohue M, Anavim A, Pribram HW. Computed tomography of Paget disease of the skull versus fibrous dysplasia. Skeletal Radiol 1998;27: 664 /72. [14] Slow IN, Friedman EW. Osteogenic sarcoma arising in a preexisting fibrous dysplasia: report of case. J Oral Surg 1971;29:126 /9. [15] Schwartz DT, Alpert M. The malignant transformation of fibrous dysplasia. Am J Med Sci 1964;247:1 /20.
