Abstract
Objective
The aim of this study was to analyze the therapeutic effect of external auditory canal stenosis caused by monostotic fibrous dysplasia of the temporal bone by operation.
Methods
Seven patients who were finally diagnosed as having monostotic fibrous dysplasia of the temporal bone by temporal bone high-resolution computed tomography (CT) and pathological diagnosis after operation underwent surgical reconstruction of the external auditory canal. The follow-up lasted 2 to 6 years, and it included pure-tone audiometry otoendoscopy, and high-resolution CT of the temporal bone. The hearing recovery and formed external auditory meatus results were retrospectively analyzed. The data were obtained from the Department of Otolaryngology in Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, from April 2003 to September 2008.
Results
We found 4 ears with combined external auditory canal cholesteatoma intraoperative. The mean pure-tone audiometries (0.5, 1, 2 kHz) and the air-bone gaps for all patients improved after 6 months postoperation. The result was statistically significant. The average air-bone gap was improved, and the external auditory canal restenosis appeared in 1 patient after 4 years. Reconstruction of the external auditory canal was performed in this patient, and no restenosis was found in subsequent 2-year follow-up. All cases were reviewed with CT and otoendoscopy to observe the results and lesion extent, and we found that the lesion was basically stable without significant progress to the periphery major structure.
Conclusion
The monostotic fibrous dysplasia of the temporal bone and its causative external auditory meatus stenosis must be treated as early as possible to recover its patency of external auditory canal to prevent complicated cholesteatoma. Satisfaction results can be obtained from surgical reconstruction of the external auditory canal. We can excise the pathological change of the external auditory canal simply to restore auditory function and eliminate clinical symptoms such as earache, ear muffled sense, and so on. Because the development of lesions was slow during the follow-up, the complete resection of all lesions was not necessary, the external auditory canal restenosis may be operated again, and the prognosis was optimistic.
1
Introduction
Fibrous dysplasia is a benign bone lesion of unknown etiology and characterized by progressive replacement of normal bone elements by fiber-bone mesenchymal tissues. It was first described and documented by McCune, Bruch and Albright in 1937 . Present studies have shown that fibrous dysplasia is most likely to be associated with the Gs- α gene mutation. In general, there are 3 clinically variant types: monostotic fibrous dysplasia, polyostotic fibrous dysplasia, and McCune-Albright syndrome .
Fibrous dysplasia can involve the bones of the whole body, but it mostly appears in the bones of the trunk, limbs, and craniofacial bone. Of these, fibrous dysplasia of the craniofacial bone usually occurs in the maxilla and mandible. However, monostotic fibrous dysplasia of the temporal bone is uncommon, which was firstly reported by Schlumberger in 1946 . Craniofacial involvement is found in only 10% of cases of the monostotic variety, whereas temporal bone involvement is very rare, with less than 60 cases being reported in the English-language literature . In these cases, the lesion mainly involves the lateral temporal bone, causing external auditory canal stenosis or complicating cholesteatoma of the external auditory canal, but rarely involves the auditory ossicles, middle and inner ear structures, and facial nerve .
The most common clinical symptoms include ear blockage and conduction hearing loss, and some patients had earache and headache . The literature of temporal bone fibrous dysplasia is primarily the report of a case and imageology .
Various studies have shown that there are approximately 80% of temporal bone cases with external auditory canal involvement . The treatment of fibrous dysplasia is generally based on the degree of functional and cosmetic impairment. Because of the benign nature of the condition, most clinical doctors consider that the cases of uncomplicated, unilateral fibrous dysplasia with conductive hearing loss can be managed conservatively with follow-up by computed tomographic (CT) scan and auditory tests.
Several studies have suggested that the clinical cases of fibrous dysplasia are treated with surgery in case of progressive stenosis of the external auditory canal, occurrence of cholesteatoma, or other complications after a long illness history. In these cases, a surgery is necessary, feasible, and effective . However, most of these reports were sporadic case studies, and at present, there is no evaluation about surgical treatment after a long-term follow-up with relatively larger samples.
In the present study, 7 cases diagnosed with monostotic fibrous dysplasia of the temporal bone and external auditory canal stenosis were treated using canaloplasty of external auditory meatus and skin grafting with the homo-thigh full-thickness skin graft. The long-term follow-up results in terms of postoperative hearing thresholds and external auditory canal status with endoscope and high-resolution CT of the temporal bone.
2
Participants and methods
The participants were recruited from the Department of Otolaryngology, Sun Yat-Sen Memorial Hospital, between April 2003 and September 2008. Seven patients diagnosed as having monostotic fibrous dysplasia of the temporal bone were included in this study. They underwent clinical otologic and audiologic evaluation, including medical history, endoscopy, and standard pure-tone audiometry (PTA).
Conventional PTA was conducted in a standard sound-proof booth, using a 2-channel Madsen Electron 922 (MADSEN™, Denmark) audiometer and a headphone. Standard audiometric procedures were applied, and the pure-tone thresholds of each ear at frequencies of 0.25, 0.5, 1, 2, 3, 4, and 8 kHz were measured. The air-bone (A-B) gaps were calculated by taking the average gap of air conduction and bone conduction at frequencies of 500, 1000, and 2000 Hz. A hearing loss was defined as any threshold between 250 and 8000 Hz exceeded 25 dB HL.
High-resolution CT of the temporal bone and endoscopy were used for diagnosis and follow-up. The operative technique consisted of radical canalplasty and transplanted full-thick skin graft of the ipsilateral thigh to perform dermatoplasty in the operative cavity. The postauricular approach begins with a vertical incision parallel and a few millimeters posterior to the retroauricular fold. External auditory canal (EAC) skin is then elevated down to the bony annulus, and the canal skin flap is protected with a gelfoam or foil, whereas the EAC bone is drilled. The lesion was removed in the superior, anterior, and posterior aspects of the EAC, until the limits of the temporomandibular joint, facial nerve, or mastoid air cells were encountered. The bone of the EAC was drilled for all patients to create an EAC that was as large as possible. Drilling with a diameter of 10 to 15 mm is ideal. The minimum diameter should be at least 10 mm or larger whenever possible, if not limited by the temporomandibular joint, facial nerve, or mastoid air cells. Openings into the mastoid air cells were packed off with cartilage, muscle, and fascia. The skin graft that has been removed subcutaneous tissue and fat, and only dermis and epithelial layer of suitable size from ipsilateral thigh was laid to resurface the ample cavity. An otowick sponge surrounded by a sheet of silastic and iodoform gauze was kept in place for 4 weeks and was regularly soaked with otic drops on a daily basis. The follow-up period was up to 2 years. During this period, the participants had postoperation endoscopy at 1, 3, and 6 months and 1 and 2 years, respectively, whereas they had the postoperation pure-tone audiogram at 6 months and 1 year, respectively, together with temporal bone CT at 2 years after operation.
2
Participants and methods
The participants were recruited from the Department of Otolaryngology, Sun Yat-Sen Memorial Hospital, between April 2003 and September 2008. Seven patients diagnosed as having monostotic fibrous dysplasia of the temporal bone were included in this study. They underwent clinical otologic and audiologic evaluation, including medical history, endoscopy, and standard pure-tone audiometry (PTA).
Conventional PTA was conducted in a standard sound-proof booth, using a 2-channel Madsen Electron 922 (MADSEN™, Denmark) audiometer and a headphone. Standard audiometric procedures were applied, and the pure-tone thresholds of each ear at frequencies of 0.25, 0.5, 1, 2, 3, 4, and 8 kHz were measured. The air-bone (A-B) gaps were calculated by taking the average gap of air conduction and bone conduction at frequencies of 500, 1000, and 2000 Hz. A hearing loss was defined as any threshold between 250 and 8000 Hz exceeded 25 dB HL.
High-resolution CT of the temporal bone and endoscopy were used for diagnosis and follow-up. The operative technique consisted of radical canalplasty and transplanted full-thick skin graft of the ipsilateral thigh to perform dermatoplasty in the operative cavity. The postauricular approach begins with a vertical incision parallel and a few millimeters posterior to the retroauricular fold. External auditory canal (EAC) skin is then elevated down to the bony annulus, and the canal skin flap is protected with a gelfoam or foil, whereas the EAC bone is drilled. The lesion was removed in the superior, anterior, and posterior aspects of the EAC, until the limits of the temporomandibular joint, facial nerve, or mastoid air cells were encountered. The bone of the EAC was drilled for all patients to create an EAC that was as large as possible. Drilling with a diameter of 10 to 15 mm is ideal. The minimum diameter should be at least 10 mm or larger whenever possible, if not limited by the temporomandibular joint, facial nerve, or mastoid air cells. Openings into the mastoid air cells were packed off with cartilage, muscle, and fascia. The skin graft that has been removed subcutaneous tissue and fat, and only dermis and epithelial layer of suitable size from ipsilateral thigh was laid to resurface the ample cavity. An otowick sponge surrounded by a sheet of silastic and iodoform gauze was kept in place for 4 weeks and was regularly soaked with otic drops on a daily basis. The follow-up period was up to 2 years. During this period, the participants had postoperation endoscopy at 1, 3, and 6 months and 1 and 2 years, respectively, whereas they had the postoperation pure-tone audiogram at 6 months and 1 year, respectively, together with temporal bone CT at 2 years after operation.
3
Results
Table 1 summarized the general information of 7 patients who were adequately followed up. There were 4 male and 3 female patients. Their age ranged from 15 to 40 years, with a mean of 26.2 years; 3 cases were on the left sides and the other 4 were on the right sides. The duration of having this disease varied from 0.5 to 9 years. All patients underwent simple external auditory canal plasty. Only 1 of them with mastoid cavity cholesteatoma underwent down-wall radical mastoidectomy. During the operation, we found that 4 patients had a complication of cholesteatoma of the external auditory canal, which was confirmed by pathological examination. Their history was all longer than 2 years, and the longest one was 9 years, whereas the history of the other 3 patients without cholesteatoma was shorter than ½ years. All patients were diagnosed as having fibrous dysplasia of the temporal bone, which was confirmed by pathobiological examination after the operation.
