Abstract
Osteoma of the temporal bone is an unusual benign slow-growing tumour composed of mature lamellar bone. It is a single pedunculated mass that often occurs unilaterally. Osteomas of external auditory canal are more common than in the other parts of temporal bone. Clinical presentation includes ear pain, hearing loss, tinnitus or vertigo. More often these lesions are an incidental finding during radiographic evaluation. Surgical excision of the osteoma is preferred in cases with impending complications. Here, we report a 36-year-old woman who came with problems of ear discharge, ear pain, hearing loss and occasional bleeding from the ear. She was diagnosed with osteoma of temporal bone with erosion of lateral semicircular canal and facial canal. Osteoma was excised and the defective areas were reconstructed.
Keywords: Ear, nose and throat; Neurootology; Pathology
Background
Temporal bone osteoma is a rare entity. External auditory canal osteomas have been reported more often when compared with other temporal bone osteomas.1 Usually, they are asymptomatic and do not require intervention. But in certain cases, there might be involvement of vital structures and associated symptoms which needs to be managed surgically. One such case has been discussed here.
Case presentation
A 36-year-old woman came to our outpatient department with intermittent, foul smelling, purulent left ear discharge for the past 1 year and ear pain for the past 10 days. She also reported problem of hearing loss, giddiness, ringing sensation and occasional bleeding from the left ear.
Otomicroscopic examination revealed a hard mass in the external auditory canal which was sensitive to touch but did not bleed on touch. Culture and sensitivity of the ear discharge showed no growth. Pure tone audiometry at the time of admission was 76.6 dB HL mixed hearing loss in the left ear.
Investigations
Non contrast CT of the temporal bone showed two bony lesions—one in the medial aspect of left external auditory canal expanding the anterior and posterior canal walls (figure 1). Another bony lesion in the mastoid antrum with surrounding soft tissue was noted and erosion of lateral semicircular canal was visualised (figure 2). Ill-defined soft-tissue density lesion seen surrounding this bony lesion (figure 3). Ossicles were not visualised separately suggesting erosion. Erosion of tympanic and proximal mastoid segment of facial nerve noted. The remaining segments of facial nerve and cochlea were found to be normal. A diagnosis of osteoma was made with the above findings and surgical excision was planned.
Figure 1.
High Resolution Computed Tomography temporal bone. Axial section showing a hyperdense lesion in the left external auditory canal.
Figure 2.
HRCT temporal bone. Coronal plane showing erosion of left lateral semicircular canal.
Figure 3.
HRCT temporal bone showing a hyperdense lesion in the left mastoid antrum.
Treatment
Intraoperatively, tympanic membrane was found to be intact in the anterior part and covered with white debris posteriorly. External auditory canal osteoma was excised and saucerised. After clearing debris, tympanomeatal flap was identified and elevated. Ossicles could not be identified and were missing. Squamous epithelium along with keratin flakes surrounding the bony mass in the mastoid antrum was removed (figure 4). Bony mass was seen extending into the attic. Posterior canal wall was lowered and cautious drilling was done around the bony mass. Lateral and superior semicircular canal were partially eroded. There was minimal erosion of the periosteum while the endosteum was intact. Horizontal and proximal mastoid portion of facial nerve canal was found to be dehiscent. The bony mass was removed in two parts and sent for histopathological examination. Granulation tissue beneath the mass seen entering the posterior semicircular canal was removed. Temporalis fascia graft was placed over the defective areas (figure 5). Fascia graft was chosen over a bone graft since endosteum of the semicircular canal was intact. Wide meatoplasty was done and wound closed in layers.
Figure 4.
Intraoperative picture showing a bony lesion in the left mastoid antrum.
Figure 5.
Intraoperative picture showing temporalis fascia graft being placed over the defective areas.
Outcome and follow-up
Postoperatively, patient was managed with broadspectrum parenteral antibiotics. Periodic dressing was done. Histopathological report showed features of osteoma (figure 6). On follow-up, the mastoid cavity was healthy. Clinically, there was improvement in hearing and no signs of giddiness or facial asymmetry were noted.
Figure 6.
Histopathology (10×). Fragments of bone composed of predominantly lamellar bone with focal woven bone and surrounded by paucicellular fibrous stoma.
Discussion
Osteomas are rare bony neoplasms with an incidence of 0.1% to 1% of all benign tumours of skull base.2 They commonly arise in the external auditory canal while middle ear, styloid process, temporomandibular joint, internal auditory canal and mastoid are less frequent sites.3
Graham et al reviewed literature and stated that out of 53 cases of osteomas of temporal bone (elusive of external auditory canal), mastoid was found to be the most common site of occurrence.4 In our case external auditory canal, middle ear as well as the mastoid parts of temporal bone were involved. Invasion of posterior labyrinth of petrous bone has been reported by Dugert et al in the year 2010.5 Involvement of lateral semicircular canal and facial canal has been reported here. Bony erosion is attributed to cholesteatoma flakes surrounding the osteoma.
Osteomas are often compared with exostosis of external auditory canal. Exostosis and osteoma of external auditory canal show similar symptoms like pain, hearing loss, tinnitus and vertigo. It is difficult to distinguish between the two clinicoradiologically. Histopathological reports are also inconclusive.6
External auditory canal osteomas are covered with periosteum and squamous epithelium and consist of lamellated bone surrounding fibrovascular channels with minimal osteocytes. There are three types of osteoma of mastoid reported-osteoma compactum, cancellare and cartilagineum based on histology. Slow-growing wide base osteomas are compact osteomas and pedunculated faster growing are spongy osteomas.7
Aetiology of osteoma is yet to be deciphered. Few reports suggest that injury, inflammation, hormones, infection, developmental disorders and genetic defects play a role in the development of osteomas.8 Syndromic aetiologies include Gardener’s syndrome which comprises multiple intestinal polyps, mesentry fibromas, epidermoid inclusion cysts and osteomas with a tendency of occurrence in membranous bones such as maxilla and mandible.9
Osteomas of temporal bone are generally incidental findings. Ear pain, hearing loss, vertigo and tinnitus are the most common presenting symptoms. In case of a mastoid osteoma, patient may present with inability to wear spectacles. Acquired cholesteatoma secondary to osteoma are very rare and only few cases have been reported in literature. Khyoratty et al have reported such one such case in the year 2013.10
Differential diagnosis include exostosis in case of external auditory canal osteomas and Paget’s disease, osteosarcoma, osteoblastic mestastais, eosinophilic granuloma, giant cell tumour, fibrous dyplasia, calcified meningioma in case of mastoid osteoma.7 Paget’s can be distinguished radiologically with its coarsened trabecular pattern. Osteosarcoma will present as an irregular lesion with soft-tissue invasion and intracranial extension. Well-circumscribed broad-based extra axial lesions with homogenous enhancement and presence of calcifications indicate calcified meningioma. Langerhan’s cells in eosinophilic granuloma and giant cells in giant cell tumour help rule out other differentials based on histology.
Non-contrast high-resolution CT is the imaging of choice. It predominantly appears as well demarcated hyperdense lesion. Mature osteomas exhibit a central marrow. T1-weighted MRI may show a high intensity signal indicating bone marrow within the tumour.
Asymptomatic lesions can be conservatively managed. Extensive osteomas with involvement of semicircular canals or facial canal require complete surgical excision without compromise of function. Though these tumours may be slow growing, final diagnosis can be made only with histopathological reports. Hence, only surgery can provide us with a confirmatory diagnosis.
Histology shows lamellated bone with minimal osteocytes surrounding fibrovascular channels. In this case, HPE revealed lamellar bone with focal woven bone surrounded by paucicellular fibrous stroma.
Learning points.
Temporal bome osteomas are rare benign lesions.
Secondary acquired cholesteatoma overlying osteoma is extremely rare. Such cases have hardly been reported.
Preoperative radiologic assessment to identify extent of lesion along with crucial structures is mandatory prior to definitive surgery.
Surgical excision should be well planned and executed by a surgeon in order to preserve the vital structures.
Footnotes
Contributors: ND have collected data and compiled the article. VB has contributed in editing the article and management of the case. Overall supervision was by PKS.
Funding: The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
Competing interests: None declared.
Provenance and peer review: Not commissioned; externally peer reviewed.
Ethics statements
Patient consent for publication
Consent obtained directly from patient(s)
References
- 1.Watkinson JC, Clarke RW, et al. Scott-Brown’s Otorhinolaryngology and Head and Neck Surgery. In: Paediatrics, the ear, and skull base surgery. Vol 2. CRC Press, 2018. [Google Scholar]
- 2.Smud D, Augustin G, Kekez T, et al. Gardner's syndrome: genetic testing and colonoscopy are indicated in adolescents and young adults with cranial osteomas: a case report. World J Gastroenterol 2007;13:3900. 10.3748/wjg.v13.i28.3900 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.El Fakiri M, El Bakkouri W, Halimi C, et al. Mastoid osteoma: report of two cases. Eur Ann Otorhinolaryngol Head Neck Dis 2011;128:266–8. 10.1016/j.anorl.2011.03.001 [DOI] [PubMed] [Google Scholar]
- 4.Denia A, Perez F, Canalis RR, et al. Extracanalicular osteomas of the temporal bone. Arch Otolaryngol 1979;105:706–9. 10.1001/archotol.1979.00790240020005 [DOI] [PubMed] [Google Scholar]
- 5.Dugert E, Lagleyre S, Brouchet A, et al. Osteoid osteoma invading the posterior labyrinth of the petrous bone. AJNR Am J Neuroradiol 2010;31:1764–6. 10.3174/ajnr.A1910 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Carbone PN, Nelson BL. External auditory osteoma. Head Neck Pathol 2012;6:244–6. 10.1007/s12105-011-0314-7 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Parelkar K, Thorawade V, Jagade M, et al. Osteoma of temporal bone—a rare case report. IJOHNS 2014;03:252–8. 10.4236/ijohns.2014.35046 [DOI] [Google Scholar]
- 8.Baik FM, Nguyen L, Doherty JK, et al. Comparative case series of exostoses and osteomas of the internal auditory canal. Ann Otol Rhinol Laryngol 2011;120:255–60. 10.1177/000348941112000407 [DOI] [PubMed] [Google Scholar]
- 9.Harley EH, Berkowitz RG. Imaging case study of the month osteoma of the middle ear. Ann Otol Rhinol Laryngol 1997;106:714–5. 10.1177/000348949710600819 [DOI] [PubMed] [Google Scholar]
- 10.Lee D-H, Jun B-C, Park C-S, et al. A case of osteoma with cholesteatoma in the external auditory canal. Auris Nasus Larynx 2005;32:281–4. 10.1016/j.anl.2005.03.010 [DOI] [PubMed] [Google Scholar]