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Extracanalicular osteoma of the temporal bone.


Extracanalicular osteomas of the temporal bone are rare, slow-growing, benign neoplasms. Although they may occur anywhere in the temporal bone, they are most common in the mastoid area. Often, symptoms are negligible and treatment is unnecessary. However, surgical removal is indicated when growth of the osteoma causes distressing symptoms or cosmetic issues. The patient described in this report had no symptoms but underwent surgical excision of a mastoid osteoma for cosmetic reasons. At 4-month follow-up, she remains asymptomatic and recurrence-free.


Extracanalicular osteomas of the temporal bone are rare. (1-4) The mastoid area is the most common site, although these neoplasms have been reported in the squama, middle ear structures, promontory, internal auditory canal, and styloid process. (1) When Fleming studied mastoid osteomas in 1966, he found reports of only 39 cases in the English medical literature. (5) In a 1979 review of the literature by Denia et al, 41 (77%) of 53 reported cases of temporal bone osteoma were found in the mastoid region, whereas only 4 cases occurred in the squama, 4 cases in the internal auditory canal, and 1 each in the glenoid fossa, eustachian tube, petrous apex, and styloid process. (1)

These tumors are rare before puberty and occur most often in young adults, more commonly in women. (1,2,4,5) They are benign, slow-growing, and composed predominantly of mature bone. Except for cortical lesions that are seen initially as cosmetic deformities, they are usually unexpected roentgenographic findings. When an otolaryngologist discovers an osteoma, it is usually in the lumen of the frontal sinus or ethmoid capsule or, rarely, in the mastoid region. (2,3) Treatment is indicated for bothersome symptoms.

This report presents a new case of mastoid osteoma in a young woman who was asymptomatic but underwent surgical treatment for cosmetic reasons.

Case report

An 18-year-old woman presented with slowly increasing swelling behind the left ear (figure 1) of three years' duration. She had no history of trauma or ear infection, and the swelling caused no pain, earache, aural discharge, vertigo, or hearing loss.

On examination, the postaural swelling was nontender, hard, and had well-defined margins. Overlying skin was free and showed no signs of inflammation. The rest of the ENT examination, audiometric testing, and routine laboratory investigations produced normal results, and there were no other remarkable features on general physical examination. Computed tomography (CT) showed a bony mass arising from the mastoid region of the left temporal bone (figure 2, A), which was well pneumatized (figure 2, B).

Surgical excision under general anesthesia was carried out for cosmetic purposes. The tumor was exposed by postaural incision. It was sessile, covered by a layer of periosteum, and firmly attached to the mastoid cortex. A clear line of demarcation between the tumor and underlying normal bone was visible. Superficial lesions of the mastoid and squama were drilled until normal mastoid air cells were reached. No underlying structures were involved.

The tumor was about 3 x 3 cm, hard, and ivory white in appearance. Histopathologic examination revealed mature, dense lamellar bone (figure 3). The diagnosis was osteoma.

The patient was free of symptoms in the postoperative period and free of recurrence at 4-month follow-up.


Temporal bone osteomas probably develop from preosseous connective tissue, but their etiology has not been established. A variety of potential inciting factors have been suggested. (1) Friedberg considers trauma, with subsequent ossifying periosteitis and chronic inflammation, to be a predisposing factor. (4) Stuart suggests a pituitary influence. (6) Yamasoba et al, who reported a case of osteoma arising from the pyramidal eminence combined with congenital cholesteatoma, suggests a congenital mechanism. (7)


Because of their slow growth, osteomas may remain stable for many years. Superficially, they are smooth on palpation and have a characteristic hard, bony consistency. The overlying skin is unaffected. (1) Tumors in the mastoid region are typically solitary and grow from the outer surface of the cortex, producing external swelling. (4) However, Morocco reported a case of multiple osteomas of the mastoid process that were growing from the inner table. (8)

Classifications. Osteomas have been classified into three types on the basis of gross specimen examination: nonmovable, with a firmly attached broad base (the most common type); movable, often with a pedicle or a pseudarthrosis; and movable with no attachment. (8)

Pathologically, osteomas may be divided into four types (8):

* Osteoma compactum, also called osteoma eburneum (the most common type), is hard, ivory-like, spherical, and attached to the cortex of the mastoid process. It may even penetrate into the cells of the mastoid process. Histologically, it has dense, lamellated bony tissue traversed by few vessels.

* Osteoma cancellare (exceedingly rare) consists of cancellous bone plus fibrous cellular tissue.

* Osteoma cartilagineum (uncommon) consists of bone and cartilage.

* Osteoma mixture (uncommon) is a mixture of the types of bone found in osteoma eburneum and osteoma cancellare.


Patient presentation. Osteomas may cause no disturbance whatsoever or may produce definitive pressure symptoms. Irritation of the greater auricular and small occipital nerves may cause referred pain to the ear, eardrum, or neck. The tumor may infiltrate the forward cortex, causing the posterior meatal wall to be pushed forward and downward, thereby causing conductive deafness. (2) Occasionally, pain or tenderness on pressure is found, particularly if the extension medially involves the inner table of the skull. (4) Fleming reported a case of osteoma of the mastoid process associated with unilateral hypertrophy of the mandible. (5)

Middle ear osteomas are very rare. They may interfere with ossicular-chain mobility and thus produce a conductive hearing loss. Glasscock et al reported a case of middle ear osteoma arising from the hypotympanum and partially immobilizing the ossicular chain. (9) Denia et al reported a case of middle ear osteoma producing eustachian tube dysfunction. (1)


Internal auditory canal osteomas also are very rare. In a 1994 study, Clerico et al found only 12 reported cases in the world literature. (10) Symptoms are those of eighth nerve compression, including unilateral hearing loss and vestibular weakness, thus mimicking symptoms of acoustic neuroma. Additional symptoms, which are variable, may include asymmetric sensorineural hearing loss (progressive or sudden), vertigo, tinnitus, facial nerve palsy, and imbalance. (11)

Osteoma occurrence may be syndromic or nonsyndromic. Infrequently, osteomas occur as a feature of Gardner syndrome. (12)

Treatment. When symptoms are present, treatment is indicated. (1) Drilling superficial lesions of the mastoid and squama is a simple procedure. These lesions are limited to the external cortex, so a cleavage plane where the tumor meets normal bone is readily encountered. In mastoid osteomas involving the facial canal or bony labyrinth, complete removal of the lesion is not recommended because damage to the structures is likely. (1)

Tumors involving the middle and inner ear are usually small and tend to remain small, (1) so observation is preferred when symptoms are absent. When there is a functional disorder, such as hearing loss or vertigo, judicious removal of the tumor can be undertaken. (9,12)

Surgical management of internal auditory canal osteomas has varied. Both middle cranial fossa and suboccipital approaches have been employed. The approach used depends, in part, on the location and size of the lesion and the preference and experience of the surgeon. (10)


(1.) Denia A, Perez F, Canalis R, Graham MD. Extracanalicular osteomas of the temporal bone. Arch Otolaryngol 1979;105(12):706-9.

(2.) Cinelli AA. Osteoma eburneum of the mastoid. Arch Otolaryngol 1941;33:421-4.

(3.) Coates GM. Osteoma growing from mastoid cortex. Arch Otolaryngol 1938;28:27-8.

(4.) Friedberg S. Osteoma of the mastoid process. Arch Otolaryngol 1938;28:20-6.

(5.) Fleming JE Osteoma of the mastoid. Can J Surg 1966;9(4):402-5.

(6.) Stuart EA. Osteoma of the mastoid. Arch Otolaryngol 1940;31: 838-54.

(7.) Yamasoba T, Harada T, Okuno T, Nomura Y. Osteoma of the middle ear: Report of a case. Arch Otolaryngol Head Neck Surg 1990;116 (10):1214-6.

(8.) Morocco WA. Multiple osteoma o f mastoid cavity. Arch Otolaryngol 1948;47:673-7.

(9.) Glasscock ME 3rd, McKennan KX, Levine SC. Osteoma of the middle ear: A case report. Otolaryngol Head Neck Surg 1987;97(1):64-5.

(10.) Clerico DM, Jahn AF, Fontanella S. Osteoma of the internal auditory canal: Case report and literature review. Ann Otol Rhinol Laryngol 1994;103(8 Pt 1):619-23.

(11.) Estrem SA, Vessely MB, Oro JJ. Osteoma of the internal auditory canal. Otolaryngol Head Neck Surg 1993;108(3):293-7.

(12.) Harley EH, Berkowitz RG. Osteoma of the middle ear. Ann Otol Rhinol Laryngol 1997;106(8):714-15.

Borlingegowda Viswanatha, MS, DLO

From the Department of ENT, Victoria Hospital and Bangalore Medical College, Bangalore, Karnataka, India

Corresponding author: Borlingegowda Viswanatha, MS, DLO, No. 716, 10th Cross, 5th Main, MC Layout, Vijayangar, Banglore, 560040, Karnataka, India. Phone: 91-80-2338-1567; e-mail:
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Author:Viswanatha, Borlingegowda
Publication:Ear, Nose and Throat Journal
Article Type:Case study
Geographic Code:9INDI
Date:Jul 1, 2008
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