Abstract
Mucocele is an accumulation of secretion products, desquamation, and inflammation within a body cavity: Localization in the mastoid is extremely rare. Erosion of bony walls and invasion of surrounding structures expose a patient to intra‐ and extracranial complications. Proper imaging work‐up and complete removal through mastoidectomy is warranted.
Keywords: hearing loss, mastoid, mucocele, neoplasm, surgical treatment
Mucocele is an accumulation of secretion products, desquamation, and inflammation within a body cavity: Localization in the mastoid is extremely rare. Erosion of bony walls and invasion of surrounding structures expose a patient to intra‐ and extracranial complications. Proper imaging work‐up and complete removal through mastoidectomy is warranted.
1. INTRODUCTION
Mucoceles are slow‐growing cysts due to distension of a hollow organ or cavity with mucus. They exhibit signs of a chronic sterile infection and have the capacity to cause bony remodeling or reabsorption. Mucoceles can be primary or secondary to chronic inflammation, trauma, scarring from previous surgery, or radiotherapy and more rarely neoplasms. The obstruction of a natural drainage pathway is considered the pathogenetic basis of a mucocele, although a mucous retention cyst that gradually enlarges has been suggested as an alternative hypothesis in temporal bone.1, 2 Within temporal bone, primary or secondary mucoceles have been only rarely observed with few descriptions prevalently in the mastoid.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 We present a new case of primary mastoid mucocele that was an incidental finding during work‐up for progressive sensorineural hearing loss.
2. CASE REPORT
A 52‐year‐old man was referred for progressive right sensorineural hearing loss in the last 10 months. The patient's medical history was negative for otitis media. Tympanic membranes were normal at otologic examination. Pure‐tone audiometry confirmed high‐frequency sensorineural hearing loss that was predominant on the right side (Figure 1).
Figure 1.
Pure‐tone audiometry demonstrating asymmetric sensorineural hearing loss predominant on the right side
Magnetic resonance (MR) was scheduled to rule out a possible lesion of the inner ear and cerebellopontine angle. MR revealed a 18 × 26 mm lesion in the right mastoid that was hyperintense in T2‐weighted images and more hyperintense compared to cerebrospinal fluid in T1‐weighted images. The lesion had sharp margins without restriction of diffusion at diffusion‐weighted imaging (DWI). After gadolinium enhancement, a thin linear reactive impregnation of the margins was evident (Figure 2). The radiologist decided to complete the radiological study with high‐resolution temporal bone computed tomography (CT), which showed expansion of the mastoid walls with thickened and sclerotic bone, whereas the posterior wall adjacent to the sigmoid sinus appeared markedly thinned and softened (Figure 3). The mastoid antrum and tympanic cavity were normally ventilated (Figure 3).
Figure 2.
Axial (A) and coronal (B) T1‐weighted magnetic resonance of the right temporal bone with gadolinium enhancement. The lesion involved the center of mastoid (asterisk) and was more intense than CSF with a thin linear impregnation of margins
Figure 3.
Axial (A) and coronal (B) high‐resolution temporal bone computed tomography of the right temporal bone. Mastoid walls appeared thickened and sclerotic (arrowhead) or thinned and softened (arrow) due to progressive expansion of the mucocele
The tendency of expansion toward intracranial structures prompted us to propose surgical treatment that consisted of mastoid exploration to remove the lesion.
Intra‐operative findings revealed a cystic lesion 2.5 cm in diameter occupying the lower two‐thirds of the mastoid process (Figure 4). The lesion was filled with a watery yellowish liquid (Figure 3). The cyst was completely removed, revealing normal aspects of the other parts of the mastoid and epitympanum (Figure 4). Postoperative recovery was uneventful and hearing remained stable. Histological examination documented a simple, benign cyst. The cyst wall was fibrosclerotic with sparse areas of epithelium composed by single layer of squamous or cubic elements. The analysis of mastoid bone showed bone tissue with reactive changes characterized by nonspecific aspects of bone remodeling. Follow‐up with MR 2 years later showed no evidence of residual disease. Informed consent to report clinical data was obtained from the patient.
Figure 4.
Surgical view before and after the removal of the mucocele: A, Exposure of the lateral wall of the mucocele (asterisk) by cortical mastoidectomy. B, Mastoid cavity after removal of the mucocele; spontaneous thinning of the sigmoid sinus plate/wall is evident (arrow). The mastoid antrum (arrowhead) appears normal
3. DISCUSSION
Only a few reports of primary mastoid mucocele have been published in the literature (Table 1).3, 4, 6, 8, 9, 11 Most cases were asymptomatic and discovered due to a silent swelling that eroded the mastoid lateral or anterior wall.3, 6, 8 Symptoms correlated with an inflammatory process were sometimes reported,4, 8, 9 whereas only once was the mucocele an incidental finding as in our patient.11 The only patient where the cyst caused hearing loss was due to ear canal collapse secondary to erosion of the anterior wall of the mastoid cavity.8 Our patient can be considered primary because medical history was negative for any predisposing cause.
Table 1.
Reports of primary mastoid mucocele in the English literature
| Author | Age | Sex | Side | Symptoms | Signs | Hearing loss | Bone reabsorption | Fluid content | Cyst wall histology |
|---|---|---|---|---|---|---|---|---|---|
| Waltner & Karatay (1947)3 | 17 | M | Left | No | Postauricular painless swelling | No | Mastoid cortex, ear canal, tegmen antri, sinodural angle | Dark, brownish lipiodol‐like | Low cuboidal epithelial lining |
| Richardson (1956)4 | 34 | F | Left | Sore throat, chills, fever, recurrent malaise | Lymph node enlargement | No | No | Sanguineous material | Endothelial cells, fibrous tissue, inflammatory cells, connective tissue |
| Nomura et al (1971)6 | 28 | F | Left | No | Postauricular painless swelling | No | Tegmen antri | Dark, greenish brown serous | Multiloculated, mostly no epithelial lining only in small part cuboidal epithelium |
| Kavanagh et al (1986)8 | 35 | M | Right | Ear discharge, canal occlusion | Skin thickening, external ear canal collapse | Conductive | Ear canal and posterior mastoid wall | Dark, serous | Dense fibrocollagenous tissue, inflammatory cells, areas of single layer of transitional cells from squamous to cuboidal, areas of multiple layers |
| Hwang & Jackler (1998)9 | 24 | F | Left | Hemifacial twitch, "burning" dysgeusia, otalgia | No | No | Facial canal | Clear, straw‐colored | Mucocele confirmed |
| Tan et al (2013)11 | 34 | F | Left | No | No | No | No | Clear, watery fluid and fibrinous exudate | Simple, benign cyst with a fibrous wall, which was low in cellularity and devoid of epithelium along its internal aspect. The cystic wall was lined with occasional lymphocytes and foam cells |
| Present case | 52 | M | Right | Sensorineural hearing loss | No | Sensorineural | Posterior mastoid wall | Watery yellowish | Fibrous tissue, areas with squamous or cuboidal cells |
The main feature of a mucocele is expansion of the cavity where it is contained, causing bone erosion or bone remodeling. It has been postulated that these effects on the bone can be due not only to the direct effects of positive pressure within the mucocele, but also to the effect of various cytokines detected in the fluid or at the interface between the paranasal sinus mucocele and bone.12
Differential diagnosis of lesions causing erosion of the temporal bone includes inflammatory lesions such as cholesterol granuloma or cholesteatoma, extracranial cysts like epidermoid or dermoid cysts, intracranial lesions such as epidermoids or subarachnoidal cysts, histiocytosis, lymphoproliferative disorders, and solid tumors like schwannomas, tympanic‐jugular paragangliomas, meningiomas, gliomas, giant cell tumors, osteomas, ossifying fibromas chordomas, and primary or metastatic carcinomas.2, 11, 13
Adequate radiological assessment is based on CT and MR. Complete opacification, an enlarged cavity with bony defects, and sometimes peripheral calcifications and possible peripheral enhancement, if a contrast agent is administered, are the features seen by CT.2, 11 The MR signal is variable according to the proportions of water, mucus, and protein: A low signal in water‐rich content and high signal in protein‐rich content is evident in T1‐weighted images, a high signal in water‐rich content, and a low signal in protein‐rich content in T2‐weighted images.1 The presence of hyperintense foci on DWI sequence depends on restriction of fluid content. Rim enhancement after gadolinium enhancement indicates peripheral inflammatory tissue.1
Classical treatment of mucoceles is marsupialization, enlarging the usual drainage pathways, while sparing the mucosa. In case of mastoid mucoceles, surgical treatment is indicated because of their expansive tendency causing bone erosion and invasion of surrounding structures with the risk of developing infections and intra‐extracranial complications.6 Appropriate surgical treatment is complete removal of the lesion through mastoidectomy to reduce the risk of recurrence without increasing the risk of morbidity.2, 11
In conclusion, primary mastoid mucoceles are extremely rare lesions. Diagnosis is based on complete otologic history, physical examination, and correct radiological imaging by CT and MR. The treatment of choice is surgical removal to prevent complications secondary to progressive expansion of the lesion.
CONFLICT OF INTEREST
No conflict of interest to declare.
AUTHOR CONTRIBUTIONS
DT and MS: collected the data and drafted the manuscript. LORDZ: operated the patient and revised the manuscript. All authors approved the final version to be published.
Tonni D, Sessa M, Redaelli de Zinis LO. Primary mucocele of the mastoid: An incidental finding. Clin Case Rep. 2020;8:461–465. 10.1002/ccr3.2690
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