CASE REPORT J Audiol Otol 2016;20(3):179-182 pISSN 2384-1621 / eISSN 2384-1710 https://doi.org/10.7874/jao.2016.20.3.179 Neuroglial Choristoma of the Middle Ear with Massive Tympanosclerosis: A Case Report and Literature Review Hyun Joon Shim1, Yong Kyung Kang1, Yong-Hwi An1, and Young Ok Hong2 1Departments of Otorhinolaryngology-Head and Neck Surgery, 2Pathology, Eulji University School of Medicine, Eulji Medical Center, Seoul, Korea Received May 17, 2016 Neuroglialchoristoma is a rare cerebral heterotopia typically involving extracranial midline Revised July 27, 2016 structures of the head and neck, including the nose, nasopharynx and oral cavity. It rarely Accepted August 16, 2016 involves non-midline structures, such as the middle ear, mastoid and orbit. We report the Address for correspondence case of a 63-year-old woman with right-sided hearing loss and aural fullness who was di- Hyun Joon Shim, MD, PhD agnosed with neuroglialchoristoma of the middle ear and mastoid. To our knowledge, this Department of Otorhinolaryngology- is the first report on neuroglialchoristomawith massive tympanosclerosis. The presence of Head and Neck Surgery, combination supported the inhalation theory of neuroglialchoristoma, given that tympa- Eulji University School of Medicine, nosclerosis is typically caused by Eustachian tube dysfunction. Eulji Medical Center, J Audiol Otol 2016;20(3):179-182 68 Hangeulbiseok-ro, Nowon-gu, Seoul 01830, Korea KEY WORDS:0 Choristoma · Middle ear · Neuroglia · Encephalocele. Tel +82-2-970-8276 Fax +82-2-970-8275 E-mail [email protected] Introduction with massive tympanosclerosis. To our knowledge, no cases on this combination have been previously reported and this Choristoma is the presence of a histologically normal tis- combination mightsupport the inhalation theory of neurogli- sue in an abnormal location. A mature brain tissue present at alchoristoma, given that poor aeration of the middle ear is a a site isolated from the cranium or spinal cord is termed as major cause of tympanosclerosis [3]. We report a case of neu- neuroglialchoristoma or heterotopic neuroglial tissue [1]. roglialchoristoma of the middle ear with massive tympano- Neuroglialchoristomas usually occur in extracranial midline sclerosis and a review of the relevant literature. structures, such as the nasopharynx, nose and oral cavity, and are rarely located in non-midline extracranial structures, such Case Report as the middle ear, mastoid and orbit. Although the pathogene- sis of neuroglial choristomas of the middle ear is unclear, brain A 63-year-old woman presented with right-sided hearing tissue herniation followed by absorption of their connection loss, which persisted since her early childhood. There was no with the brain tissue is the most accepted hypothesis. So, the history of congenital anomalies, trauma or ear surgery. Oto- only difference between neuroglialchoristomas and encepha- scopic examination revealed a moderate-sized tympanic mem- loceles is that the former lack a direct connection with the brane perforation of the right ear and small-sized tympanic central nervous system [2]. We recently experienced a case of membrane perforation of the left ear. Pure tone audiometry neuroglialchoristoma of the middle ear and mastoid antrum showed mixed-type hearing loss in both ears. Computed to- mography revealed a soft tissue density with massive calcifi- This is an Open Access article distributed under the terms of the Cre- ative Commons Attribution Non-Commercial License (http://creative- cation in the middle ear, leading to the suspicion of bony ero- commons.org/licenses/by-nc/3.0/) which permits unrestricted non-com- sions in the tegmen tympani of the right ear (Fig. 1). During mercial use, distribution, and reproduction in any medium, provided the original work is properly cited. canal-wall-down mastoidectomy and tympanoplasty, a well- Copyright © 2016 The Korean Audiological Society 179 Neuroglial Choristoma with Tympanosclerosis cleavable vascular mass resembling a schwannoma was de- tory lesion showing fibrous stroma or a neuroglial tissue was tected in the middle ear and mastoid antrum (Fig. 2A). A sub- diagnosed despite its rare occurrence. The incus and stapes sequent frozen section resulted in differential diagnoses, were fixed by massive tympanosclerosis in the middle ear including an inflammatory lesion with fibrous stroma, a be- (Fig. 2B). Following the incudostapedial joint separation, the nign spindle-cell lesion, such as schwannoma, and possibly a incus and tympanosclerosis were excised. Although tegmen neuroglial tissue (Fig. 3A). Because the stromal cellularity is erosion over the attic was revealed during surgery, no cere- very low and insufficient to identify a spindle-cell lesion, the brospinal fluid (CSF) leaks or connections with the brain presence of a schwannoma was less likely. Based on the as- were observed. The tumour mass was well-separated from sessment of the intraoperative frozen sections, an inflamma- the intact facial canal in its tympanic segment. The final diag- Fig. 1. A: Axial temporal bone com- puted tomography demonstrates soft tissue density with massive calcifi- cation in the middle ear (black ar- row). B: Coronal temporal bone com- puted tomography demonstrates bony erosion of the tegmen tympani A B (white arrow). Fig. 2. A: Intraoperative findings. Tegmen (black arrow) and a well- cleavable mass (white arrow) in the epitympanum. B: Incus (white ar- row) aggregating massive tympano- sclerotic plaque (white arrowhead) A B in the mesotympanum. A B C Fig. 3. Histologic features of the lesion. A: The frozen biopsy specimen comprising scattered mononuclear cells of various sizes and shapes against a fibrillary background (H&E, ×200). B: Immunohistochemical staining revealed immunopositivity for glial fibrillary acidic protein staining (×200). C: Calcific lesion with woven bone formation and fibrous area( H&E, ×40). 180 J Audiol Otol 2016;20(3):179-182 Shim HJ, et al. nosis of a neuroglialchoristoma was made based on a diffuse distant location, these cells then form a mass of ectopic brain immunopositive reaction for glial fibrillary acidic protein tissue resembling a neural crest remnant [12]. Several such (GFAP, mouse monoclonal antibody, Clone, DP46.10; diluted, cases at a very young age with intact tympanic membranes 1:100, Signet; Dedham, MA, USA) (Fig. 3B). The diffusely and no history of otitis media advocate high possibilities of calcified lesion showed woven bone formation and scant fi- congenital development. brous tissue consistent with the diagnosis of tympanosclerosis According to the inhalation theory on the development of (Fig. 3C). neuroglial choristomas, the tegmen defect seems to be an im- portant process. Spontaneous tegmen defects are less com- Discussion mon in adults, and chronic otitis media with or without cho- lesteatoma is the most common cause of tegmen defects in The most common type of choristoma in the mastoid or adults. Other causes include temporal bone trauma, neoplasia, middle ear is the salivary choristoma and the rarest is the and radiotherapy [13]. Meanwhile, eustachian tube dysfunc- neuroglialchoristoma. Neuroglialchoristomas are often classi- tion and poor aeration of the middle ear cavity are the major fied according to their location and possible aetiopathogenesis predisposing factors of not only chronic otitis media [14] but as follows: intraparenchymalcentral nervous system lesions, also tympanosclerosis. Otitis media with or without effusion dural and leptomeningeal lesions, intracranial extracerebral le- may lead to a destructive process within the connective tissue sions, distal lesions considered to result from a previous preg- of the middle ear, which leads to the degeneration of collagen, nancy, midline nasal gliomas and non-midline lesions of the subsequent dystrophic calcification, and tympanosclerosis head and neck. Based on our literature review, neurogliomas [15]. Wielinga, et al. [3] demonstrated this using an experi- of the middle ear and mastoid have previously been de- mental animal model of tympanosclerosis induced by Eusta- scribed in only 32 cases. Symptoms of choristoma of the chian tube dysfunction, wherein the dysfunctioninduced pro- middle ear include hearing loss, otorrhea, ear fullness, tinni- longed otitis media with effusion, tympanic membrane fibril tus and otalgia. Although the etiology and development pro- degeneration, an increase in fibroblast activity, abnormal fi- cess of neuroglial choristomas are unclear, the most accepted brils formation and subsequent large hyalinized plaque for- hypothesis is the inhalation theory. According to this theory, mation. In our present case, negative pressure by eustachian brain tissue herniation known as encephalocele may occur as tube dysfunction may have induced chronic otitis media, a spontaneous lesion or as a result of bone and dural defects causing the tegmen defect followed by subsequent develop- by trauma, infection, or neoplasm. When a pedicle directly ment of choristoma. Simultaneously, long-lasting negative connecting the neuroglial tissue with the subarachnoid or pressure and chronic inflammation are assumed to induce ventricular spaces may become detached and eventually get massive tympanosclerosis. Based on this putative pathogene- absorbed or become vestigial, an isolated ectopic mass of sis, neuroglial choristoma combined with tympanosclerosis brain tissue develops. Based on this theory, neuroglial choris- of the middle ear could be a case that strongly supports