External auditory canal osteoma: a case report

INTRODUCTION

Osteoma in the EAC manifests as a rare benign tumour, which is solitary, unilateral and slow growing pedunculated mass in the bony canal.¹ It shows a predilection for the EAC, mastoid cortex, facial bones and mandible.² Its incidence is 0.05% of total otologic surgery.³ Chronic irritation/inflammation to the inner part of the EAC leads to ingrowth of the bone through suture lines. Osteoma of ear canal are usually incidental finding and they are unilateral and solitary. They show clinical presentations such as hearing loss, otorrhea, otalgia, otitis externa and cholesteatoma. Diagnosis is made based on a combination of clinical history and examination, radiographic imaging, and histopathology. Differential diagnosis includes exostosis, adenoma, hard cerumen, foreign body, xanthogranuloma and other benign fibro-osseous lesions.

CASE REPORT

A 21-year-old male patient came to our out-patient department with complaints of left aural fullness for 6 months, which was insidious in onset, progressive, with no aggravating or relieving factors. It was associated with decreased hearing. History of habitual use of ear buds present. No history of swimming, trauma, ear discharge or ear pain. On otoendoscopic examination, a bilobed mass that was completely obscuring the ear canal was noted, which was hard in consistency and non-tender (Figure 1). Tympanic membrane in the left side could not be visualized, right side was normal.

HRCT of temporal bone showed a pedunculated bony osteoma arising from the anterior wall of left EAC measuring 6.5×4×9 mm, with underlying cerumen (Figure 2 and 3). Pure tone audiometry showed moderate conductive hearing loss (46 db HL) in the left side.

Patient underwent excision of left EAC osteoma through a post auricular approach under general anesthesia (Figure 4). Osteoma was removed through its peduncle and raw area was covered with skin flap (Figure 5). The specimen was sent for histopathological evaluation. Post operative period was uneventful.

Histopathological examination reports confirmed the specimen to have features suggestive of osteoma with areas of lamellated bone, bone marrow and few fibrovascular channels (Figure 6).

DISCUSSION

The solitary osteoma is an uncommon unilateral lesion, attached to the tympansquamous or tympanmastoid suture line, almost always in the outer half of the ear canal. It is seen commonly in the second decade of life and can be seen in a wide range of age groups.³ Osteomas of temporal bone are rare, and have been reported in the middle ear, internal auditory canal, squamous temporal bone, mastoid, internal auditory canal, cerebellopontine angle and in the EAC.⁴ Most common suggested eitiology of osteoma are trauma, chronic infection, and hormonal dysfunction.^5-7 Graham showed that the most common site of origin of EAC osteomas is from the vascular pre-osseous connective tissue in the tympan squamous or tympan mastoid suture lines.¹ Kim et al reported osteoma mostly originated in the tympanic wall, and this is regardless of the tympano-squamous or tympano-mastoid suture line.⁸

The most common clinical entity that shares a very similar picture with osteoma in terms of presentation is exostosis. The differentiation between these two are still a dilemma. Exostosis are multiple, bilateral, appear as wide based and smooth lesions of the EAC and are usually considered to be a reactive condition secondary to multiple cold-water immersions or recurrent otitis externa.^9,10

There are limited histopathological studies done for osteoma and exostosis as these lesions are drilled during surgical removal. Exostosis are concentric, dense layers of subperiosteal bone with abundant osteocytes, lacking fibrovascular channels covered with periosteum and squamous epithelium.¹ Studies by Fenton et al suggested that fibrovascular pathway is a characteristic feature of osteoma, and could also be found in exostosis also and so it could not be differentiated histopathologically.² In some cases they might also occur together.¹¹ Osteoma and exostosis has been categorized as a single clinical group, by some researchers, whereas, Schuknechts classifies the lesions limited to the EAC as exostoses and lesions that extend beyond the canal as osteoma.^12,13

The management of osteoma of EAC depends on the size, symptoms and site of origin. Regular aural toileting can be done for small, asymptomatic lesions. Excision of the osteoma must be actively considered as the treatment of choice in symptomatic patients with large lesions. The location of the osteoma in relation to the isthmus of the EAC is the main deciding factor for surgery. A post-auricular approach is used for medially placed osteoma and a trans-canal approach for laterally placed neoplasm.¹⁴ The approaches used are post aural, endaural and trans-meatal. Though the most preferred route was post aural due to better exposure and complete removal, nowadays with the advent of endoscopes and better equipment, minimally invasive trans-meatal route is now being preferred for EAC osteoma and exostosis removal.³ The osteoma is usually excised through its pedicle and the base is drilled to decrease the incidence of recurrences.⁵ Grinblat et al performed drill canaloplasty in 245 cases of EAC osteomas and exostosis and reported no recurrence in their cases.¹⁵ Some of complications encountered during the removal of EAC osteoma are as follows: EAC posterior wall injury, tempero-mandibular joint injury, ear drum and ossicular injury, peripheral paralysis of facial nerve and chorda tympani damage, sensorineural hearing loss and narrowing of canal lumen.

Piezoelectric device is a new innovation in the field of osteoma surgery. It is a bony scalpel that uses micro vibrations at ultrasonic frequency so that soft tissues will not be damaged even on accidental contact with the cutting tip. With an experienced otologist the piezoelectric device is considered suitable for bone surgery and for removal osteomas of the EAC.¹⁶

Literature shows that there is increased risk of development of EAC cholesteatoma secondary to long-standing EAC obstruction and chronic inflammation, further leading to bony canal erosion and complications such as sigmoid sinus thrombosis and neck abscesses.^17-19

CONCLUSION

Thus, any symptomatic EAC osteoma is removed surgically, the approach is determined by the size, location and experience of the surgeon. Though by literature asymptomatic lesions are usually managed conservatively, based on the multiple cases reported, we can conclude that EAC osteomas, which were initially asymptomatic, if neglected could lead to complications which are life-threatening. Hence once identified these EAC lesions should be removed electively to give better prognosis.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: Not required

REFERENCES

1. 1. Graham MD. Osteomas and exostoses of the external auditory canal. A clinical, histopathologic and scanning electron microscopic study. Ann Otol Rhinol Laryngol. 1979;88(4Pt1):566-72.
2. 2. Fenton JE, Turner J, Fagan PA. A histopathologic review of temporal bone exostoses and osteomata. Laryngoscope. 1996;106:624-8.
3. 3. Sheehy JL. Diffuse exostoses and osteoma of the external auditory canal: a report of 100 operations. Otolaryngol Head Neck Surg. 1982;90:337-42.
4. 4. Gungor A, Cincik H, Poyazoglu E. Mastoid osteomas: report of two cases. Otol Neurotol. 2004;25:95-7.
5. 5. Abhilasha S, Viswanatha B. Osteomas of temporal bone: a retrospective study. Indian J Otolaryngol Head Neck Surg. 2019;71(2):1135-9.
6. 6. Mahalle S. Osteoma of external auditory canal associated with external auditory canal cholesteatoma and exuberant granulation tissue in mastoid air cell system: a rare association. Indian J Otolaryngol Head Neck Surg. 2019;71(2):1505-7.
7. 7. Gheorghe DC, Stanciu AE, Ulici A. Bilateral external ear canal osteomas: discussion on a clinical case. J Med Life. 2016;9(4):434-6.
8. 8. Kim HY, Song CJ, Yoon CD, Park MH, Shin BS. CT Findings of the Osteoma of the External Auditory Canal. Korean Radiol Soc. 2006;55(1):33-7.
9. 9. Michaels L. Neoplasms of the external ear. In: Ear, Nose and Throat Histopathology. London: Springer-Verlag. 1987;63-5.
10. 10. Bilkay U, Erdem O, Ozek C, Helvacj E, Kilic K, Ertan Y, Gurler T. Benign osteoma with Gardner syndrome: review of the literature and report of a case. J Craniofacial Surg. 2004;15:506-9.
11. 11. Baik FM, Nguyen L, Doherty JK, Harris JP, Mafee MF, et al. Comparative case series of exostoses and osteomas of the internal auditory canal. Ann Otol Rhinol Laryngol. 2011;120(4):255-60.
12. 12. Pulec JL, Deguine C. Osteomas of the external auditory canal. Ear Nose Throat J. 1993;72:112.
13. 13. Schuknecht H. Exostoses of external auditory canal. In: Pathology of the Ear. Philadelphia: Lea and Febiger. 1993;398-9.
14. 14. Fisher EW, McManus TC. Surgery for external auditory canal exostoses and osteomata, J Laryngol Otol. 1994;108:106-10.
15. 15. Grinblat G, Prasad SC, Piras G, He J, Taibah A, Russo A et al. Outcomes of Drill Canaloplasty in Exostoses and Osteoma: Analysis of 256 Cases and Literature Review. Otol Neurotol. 2016;37(10):1565-72.
16. 16. Salami A, Mora R, Dellepiane M. Piezosurgery® for removal of symptomatic ear osteoma. Eur Arch Otorhinolaryngol. 2010;267:1527-30.
17. 17. Khoyratty F, Sweed A, Douglas S, Magdy T. Osteoma with cholesteatoma of the external auditory canal: neck manifestation of this rare association. J Surg Case Rep. 2013;6:2013:rjt048.
18. 18. Ata N, Vet A, Alatas G. External auditory canal osteoma with cholesteatoma and sinus thrombosis. J Craniofac Surg. 2015;26(7):2234-5.
19. 19. Iaccarino I, Bozzetti F, Piccioni LO. A case of external auditory canal osteoma complicated with cholesteatoma, mastoiditis, labyrinthitis and internal auditory canal pachymeningitis. Acta Otorhinolaryngol Ital. 2019;39(5):358-62.