Eosinophilic granuloma of the temporal bone with extensive bilateral otic capsule involvements: Incomplete reossification despite theraphy

1. Introduction 

Langerhans’ cell histiocytosis (LCH), previously known as histiocytosis X, is a rare, proliferative disorder in which the accumulation of pathologic Langerhans’ cells lead to local tissue infiltration and destruction [1]. LCH principally affects children younger than 4 years of age, with an incidence of 0.5–5 cases per million children per year [1].

Based on the sites of involvement and extent of the disease, LCH shows various clinical manifestations [2]. The incidence of otologic manifestations in children ranges from 11% to 61%. The most common symptoms are otorrhea, mastoid swelling, deafness, and aural polyps eroding the posterosuperior canal wall [3]. These otologic findings can mimic more common diseases, including simple otitis externa, otitis media, aural polyps, acute mastoiditis, and metastatic lesions [4]. Involvement of the inner ear is rare due to compact otic capsule [5], [6], [7].

Eosinophilic granuloma (EG) or benign focal histiocytosis X is one of the three variants of LCH. The other two are Letterer-Siwe's and Hand-Schüller-Christian's diseases [8]. We report a case of bilateral temporal eosinophilic granuloma with otic capsule involvement, who was initially misdiagnosed and treated for non-specific otitis media. The diagnosis, radiologic findings and the management of this relatively rare disease are discussed.

2. Case report 

A four-year-old boy who had intermittant otorrhea in both ears during the last year attended the Ear Nose Throat Clinic. Clinical examination showed a polypoid mass which had totally filled up external auditory canal. Bilateral profound sensorineural hearing loss was diagnosed with audiological test battery. At the age of 2 years, he had earache and otorrhea in the right ear and applied to Pediatric Clinic. Examination demonstrated purulent aural discharge in the right ear and normal findings in the left ear, and the systemic medical treatment was given. The patient was lost to follow-up after that initial diagnosis of right otitis media and was treated for chronic otitis media by other institutions.

Computerized tomography (CT) scanning was performed with a 64-detector (multi-slice) CT scanner (Aquillion 64, Toshiba, Tokyo, Japan). CT showed bilateral osteolitic defects without sclerotic margins filled with soft tissue masses involving the middle ear, mastoid, squama and petrous part of the temporal bone. The involvement was worse on the right side. Bilateral bony labyrinth was involved (Fig. 1). For the differential diagnosis of cholesteatoma and LCH, Magnetic Resonance Imaging (MRI) was performed. MRI of the temporal bone revealed bilateral involvement of inner ear with internal auditory canal involvement on the right. The sof t-tissue mass was relatively isointense to hyperintense on T1-weighted images (Fig. 2a), iso-hyperintense on T2-weighted images (Fig. 2b) and showed marked enhancement after administration of contrast material (Fig. 2c). For differentiation of LCH, osteomiyelitis and malignant tumors bilateral punch biopsy was performed under general anesthesia.

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Figure 1. (a, b) Axial and coronal bone window computed tomography reveals destructive lesions of bilateral mastoid with bilateral otic capsule involvement.

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Figure 2. (a) Axial T1-weighted image (TR/TE, 525/14) shows bilaterally inhomogeneous iso-hyperintense neoplastic soft-tissue masses in the mastoid, tympanic cavity, petrous apex and otic capsule. (b) Axial T2-weighted image (TR/TE, 3635/120). The lesion is iso-hyperintense. (c) Axial gadolinum enhanced T1-weighted image (TR/TE, 624/14). There is heterogeneous enhancement.

Microscopically, the tissue fragments contained a dense cellular infiltrate consisting of Langerhans’ cells, eosinophils and scattered lymphocytes (Fig. 3a). There were small foci of necrosis. Langerhans’ cells were immunoreactive for CD1a (Fig. 3b) and s-100 protein. The histopatological and immunohistochemical findings were consistent with LCH.

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Figure 3. (a) Langerhans’ cells showing lobulated or indented nuclei with occasional longitudinal grooves admixed with eosinophils (H&E ×400). (b) Strong immunoreactivity of the Langerhans’ cells for CD1a (×400).

Mastoidectomy in the right ear was performed under general anesthesia. All mastoid cells completely blocked with the mass and lesion extended into the cochlea although the outer layer of the cochlea was intact. Postoperative pathology confirmed preoperative pathology.

Bone scintigraphy revealed no other lesions. As recommended by the French Langerhans’ cell study group [9], he was treated with vinblastine and corticosteroid by pediatric hematologist for a year because of the multifocal bone involvement.

Fourteen months later, follow-up temporal bone CT revealed no soft tissue masses on both inner ears, and the bony lesions of the temporal bone were reossified and remodeled (Fig. 4a). The right lateral (Fig. 4b) and posterior (Fig. 4c) semicircular canals were dehissent and these canals were tortious and did not complete their normal configuration. Cochlea and superior semicircular canal were normal. On the left posterior semicircular canal was irregular and dehissent (Fig. 4d). Cochlea and other semicircular canals were normal on the left.

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Figure 4. (a) Axial bone window computed tomography 14 months after medication. The bony lesions of temporal bone reossified. (b) Axial bone window computed tomography reveals that right lateral semicircular canal is dehiscence. (c) Oblique bone window computed tomography reveals that right posterior semicircular canal is dehiscence. (d) Axial bone window computed tomography reveals that left posterior semicircular canal is dehiscence.

During the follow-up temporal bone CT, bilateral profound sensorineural hearing loss was present and therapy options such as cochlear implantation were discussed with the parents and the final decision was expected.

3. Discussion 

Involvement of the temporal bone has been described in 11–61% of all cases of LCH [3]. Most authors agree that otologic involvement usually occurs during the course of multisystemic disease, although it may be the only symptom in 5–25% of patients [10]. Bilateral involvement of EG as reported here is extremely rare. It has been estimated that approximately 22 cases have been reported so far in the world literature [11].

It is not uncommon to find manifestations of inner ear lesions in adulthood [12], but involvement of the inner ear, revealed by sensorineural hearing loss, vertigo, or CT scan, has only been reported in approximately ten children [1], [3], [6], [13], [14] and most of them have a multisystem disease. In the retrospective analysis of Irving et al, 131 cases of LCH (mean age:3.2 years) were reviewed and 19% of them had temporal bone involvement but none of the cases had inner ear involvement [3].

Depending on the extent of involvement, the audiologic findings may range from normal hearing through conductive hearing loss to severe sensorineural hearing loss or even total deafness. In many cases, the symptoms are misinterpreted as otitis media, cholesteatoma, or mastoiditis [15]. Children with otitis media or mastoiditis with no response to medical treatment should be evaluated with CT scanning of the temporal bone. Our patient was lost to follow-up after his initial diagnosis of right otitis media and was treated for chronic otitis media at other institutions. Because our patient was not treated for EG, the lesion bilaterally progressed and bilateral temporal lesions probably extended to the inner ear.

CT clearly delineates both the osseous and soft-tissue components of LCH. The sharply marginated lytic lesions are readily seen on bone window algorithms and erosion of otic capsule is demonstrable [14]. Recent technical advances have introduced multidetector row CT into clinical practice. This imaging modality allows thinner section imaging, faster scanning, and improved longitudinal spatial resolution than does single detector-row helical CT [16]. Chuang et al. demonstrated the cochlea and the three semicircular canals (anterior, posterior, and lateral) well in 29 (97%) of 30 patients with 16-channel multidetector row CT scanner [17]. In the literature most of the temporal LCH involvements were demonstrated with single slice CT scanners. In this case usage of multi-slice CT made us to demonstrate the dehiscence of semicircular canals after medication. In the retrospective study of 14 patients, Fernandez Latorre et al. found 4 cases of bilateral temporal involvement and two had involvement of the bony labyrinth without dehiscence of semicircular canals and after medication with local steroids complete reossification was achieved [10]. As we know in the literature there is not any case in which the dehiscence and disruption of semicircular canals is shown after treatment of LCH.

The soft-tissue component can also be shown favorably by MRI. The lesions appear isointense on T1 weighting and hyperintense on T2 weighting. Contrast medium administration is followed by inhomogeneous enhancement with zones of central hypointensity [18]. In this case MRI findings were compatible with former MRI findings.

When bilateral temporal involvement is present, clinical presentation and radiologic findings can be diagnostic for LCH but definite diagnosis is established at biopsy.

Classically, local treatment of Langerhans’ cell histiocytosis of the temporal bone included mastoidectomy and radiotherapy, although the current tendency is to use local steroid injection. Treatment of the multisystemic form includes chemotherapy, steroid injections, and immunotherapy [9]. Various chemoterapy protocols are available for the treatment of systemic LCH. In this context, the cytotoxic agents vinblastine, etoposide, or methotrexate are used in combination with prednisone [11]. Our patient's bony lesions of the temporal bone incompletely reossified and labyrinthine function was not satisfactory after mastoidectomy and chemotherapy with vinblastine and prednisone. We think this is because of late diagnosis of LCH. If the diagnosis could be established earlier, complete remission with proper medication could be achieved.

4. Conclusion 

The children with otitis media or mastoiditis with no response to medical treatment should be evaluated with CT scanning of the temporal bone.