Otology & Neurotology 36:e156–e158 ß 2014, Otology & Neurotology, Inc.

Imaging Case of the Month

HASTE Diffusion-Weighted Magnetic Resonance Imaging of Middle Ear Teratoma Francisca Leo´n, Andre´s Alvo, David Sanhueza, yPaul H. De´lano, and Carlos E. Stott Departamento de Otorrinolaringologı´a, Hospital Clı´nico de la Universidad de Chile; and yPrograma de Fisiologı´a y Biofı´sica, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile

In recent years, diffusion-weighted magnetic resonance imaging (DW-MRI) has acquired a growing role in the diagnosis of middle ear cholesteatomas based on the restrictive pattern produced by the keratinized epithelial content. Conventional echo-planar (EPI) DW-MRI has been replaced by non-EPI DW-MRI sequences because they minimize susceptibility artifacts at the skull base and increase sensitivity for detection of cholesteatomas as small as 2 mm. Several authors have reported a high sensitivity and specificity (>90%) for the diagnosis of primary and secondary cholesteatomas with the HASTE protocol (a non-EPI DW-MRI sequence abbreviated from half-Fourier acquisition single-shot turbo spinecho) (1). Although the non-EPI DW-MRI sequence has been proposed as a key imaging technique for the diagnosis of congenital cholesteatoma, there is still little experience because only a few cases have been reported in the literature (1,2). Here, we present a case that had a preoperative diagnosis of congenital cholesteatoma with a positive HASTE DW-MRI, but the presence of a hairy polyp and dental tissue found during surgery, in addition to the histological analysis, confirmed the diagnosis of a mature middle ear teratoma.

revealed the presence of a small bone dehiscence in the tegmen tympani (not shown) and that the left mastoid air cells and middle ear cavity were completely opacified. In addition, there was a lesion narrowing and protruding into the external canal along the superior wall. The MRI demonstrated the presence of a large mass extending from the subcutaneous tissue surrounding the external ear canal to the middle ear and mastoid (Fig. 1). The patient was scheduled for a left radical mastoidectomy, planning the complete resection of the middle ear congenital cholesteatoma. Electrophysiological monitoring of the facial nerve was not used. During surgery, a hairy polyp was found in the posterior-superior wall of the external ear canal, whereas cartilage and dental-like tissue were found in the middle ear cavity, and an intraoperative biopsy was assessed and reported as a mature cystic teratoma. The teratoma was resected using a canal wall-down mastoidectomy, and a cerebrospinal fluid fistula produced intraoperatively in the tegmen tympani was repaired with fat during the same procedure. Unexpectedly, during surgery, we found that the tumor surrounded the mastoid segment of the facial nerve and the patient developed a facial nerve paralysis postoperatively with no recovery (House-Brackmann 6/6 score). Hearing thresholds did not change significantly after surgery. Follow-up MRI studies demonstrate no evidence for tumor recurrence at 6 months after surgery.

CASE REPORT An 18-year-old woman with no previous medical history was referred for left-sided hearing loss during the last year. Physical examination showed a noninflammatory swelling of the posterior wall of the external ear canal, with a normal tympanic membrane. Audiometry revealed a left-sided conductive hearing loss (56.6/5.4 dB air and bone average thresholds, respectively). A congenital middle ear cholesteatoma was suspected, and computed tomography (CT) and MRI, including HASTE-DW sequence, were performed. The CT images

DISCUSSION Traditionally, the diagnosis of middle ear cholesteatoma is based on physical examination and temporal bone CT. In the last decade, several reports have demonstrated high sensitivity and specificity (>90%) of HASTE DWMRI for the diagnosis of cholesteatomas larger than 2 mm, superior to those of conventional MRI. In addition, HASTE DW-MRI does not require the use of intravenous gadolinium (1,2). There are only a few false-positive cases of DW-MRI reported in the literature, including middle ear abscesses,

Address correspondence and reprint requests to Carlos E. Stott, M.D., Otorhinolaryngology Department, University of Chile, Santos Dumont 999, Independencia, Santiago, Chile; E-mail: [email protected] The authors disclose no conflicts of interest

e156

Copyright © 2015 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.

HASTE DW-MRI OF MIDDLE EAR TERATOMA

e157

FIG. 1. Imaging of middle ear teratoma. A, Axial CT, left mastoid cells and middle ear cavity are completely opaque, with bony features (not ossicles) within the middle ear (white arrow). B, Coronal CT, in addition to the middle ear opacity; notice a mass protruding into the external canal from the superior wall (white arrow). C, The mastoid portion of the teratoma is shown with similar MRI sections in C1 and C2 panels, with coronal T2-weighted and T1-weighted gadolinium-enhanced MRI correspondingly. Note that, in panel C2, a contrast-enhancing rim of the lesion is observed (white arrow). D, Coronal T1-weighted gadolinium-enhanced MRI; there is no contrast enhancing of the subcutaneous portion of the teratoma (white arrow). E, Coronal ADC map section; there is a hypointense signal in the subcutaneous region of the teratoma (white arrow). F, Coronal HASTE DW-MRI of the teratoma in the same plane as ADC map showed in E. Notice the presence of a hyperintense granular pattern (white arrow) located in the subcutaneous segment of the tumor, but less intense than the images commonly associated with cholesteatoma (2).

bone powder, and cholesterol granulomas (1,2); however, to our knowledge, this is the first case of a middle ear teratoma with positive findings in the HASTE DW-MRI.

Teratomas are tumors composed of three germ cell layers (ectoderm, mesoderm, and endoderm) that are typically found in the cervical region when occurring in the head and neck. Involvement of the middle ear is Otology & Neurotology, Vol. 36, No. 10, 2015

Copyright © 2015 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.

e158

F. LEO´N ET AL.

rare, with the majority of cases reported in the literature occurring in female children. These tumors should be considered in the differential diagnosis of a congenital cholesteatoma, especially when compromise of the Eustachian tube is observed (3,4). Previous studies of mature teratomas evaluated with CT showed a bone destructive mass located in the middle ear and sometimes associated with an encapsulated tooth (4,5), whereas MRI demonstrated the presence of a cystic lesion with heterogeneous signal in T2 and with a T1-gadolinium enhancing rim. In the present case, we had similar findings on the T2-weighted and contrast-enhanced T1-weighted sequences at MRI but, in addition, we observed hyperintense signal on the HASTE-DW sequence with hypointense signal in the apparent diffusion coefficient (ADC) map, consistent with restricted diffusion in the subcutaneous portion of this tumor. We propose that, in the HASTE DW-MRI evaluation of a congenital cholesteatoma, the presence of a diffuse positive HASTE with a granular and less intense pattern than which is expected for a cholesteatoma suggests the presence of a middle ear teratoma. This phenomenon could be explained by the ectodermal component of the mature teratoma, which may explain the punctate

hyperintense signal consistent with restricted diffusion observed on the HASTE DW imaging. Further teratoma cases studied with HASTE DW-MRI are needed to confirm this proposal, but given that nonEPI DW-MRI is becoming the standard in the evaluation of congenital cholesteatomas, the presence of a granular pattern of restricted diffusion within the lesion on HASTE DW-MRI could suggest the presence of a middle ear teratoma. REFERENCES 1. Li PM, Linos E, Gurgel RK, Fischbein NJ, Blevins NH. Evaluating the utility of non-echo-planar diffusion-weighted imaging in the preoperative evaluation of cholesteatoma: a meta-analysis. Laryngoscope 2013;123:1247–50. 2. Ma´s-Estelle´s F, Mateos-Ferna´ndez M, Carrascosa-Bisquert B, Facal de Castro F, Puchades-Roma´n I, Morera-Pe´rez C. Contemporary non-echo-planar diffusion-weighted imaging of middle ear cholesteatomas. Radiographics 2012;32:1197–213. 3. Ruah CB, Cohen D, Sade´ J. Eustachian tube teratoma and its terminological correctness. J Laryngol Otol 1999;113:271–4. 4. Roncaroli F, Scheithauer BW, Pires MM, Rodrigues AS, Pereira JR. Mature teratoma of the middle ear. Otol Neurotol 2001;22:76–8. 5. Bowyer DJ, Wilson J, Sillars HA. Mature teratoma of the eustachian tube. Otol Neurotol 2012;33:e43–4.

Otology & Neurotology, Vol. 36, No. 10, 2015

Copyright © 2015 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.

HASTE Diffusion-Weighted Magnetic Resonance Imaging of Middle Ear Teratoma.

HASTE Diffusion-Weighted Magnetic Resonance Imaging of Middle Ear Teratoma. - PDF Download Free
167KB Sizes 0 Downloads 5 Views