CASE 2151 Published on 09.11.2005

Glomus tympanicum

Section

Head & neck imaging

Case Type

Clinical Cases

Authors

Kumar DS , Pai DM, Yeong CC

Patient

57 years, female

Categories
No Area of Interest ; Imaging Technique CT, CT
Clinical History
A patient presented with pulsatile tinnitus in the right ear, which she had had for a few years.
Imaging Findings
The patient presented with pulsatile tinnitus in the right ear, which she had had for a few years. An otoscopic examination of the right ear revealed a well defined mesotympanic mass, and the left ear was found to be normal. A contrast enhanced helical CT scan was performed, acquired axially at isometric (0.5 mm collimation) resolution with coronal reconstruction. The CT scan revealed a small, enhancing mass in the middle ear cavity, lying against the cochlear promontory, without connection to the jugular fossa.
Discussion
Glomus tumours at the level temporal bone may arise from non-chromaffin para ganglia or glomus bodies, located in the adventitia of the dome of the jugular bulb, along the course of the tympanic branch of the glossopharyngeal nerve (jugular fossa to promontory in the middle ear), or along the course of the auricular branch of the vagus nerve (jugular fossa to descending portion of the facial nerve). Glomus tumours that arise from the middle ear are termed as glomus tympanicum and those that arise from jugular fossa are called glomus jugulare tumours (1). Their clinical presentation results from expansion into the areas around the site of origin. Patients with tumours in the middle ear present with tinnitus and deafness. The glomus jugulare can present with lower cranial nerve lesions, a mass in the upper part of the neck, and symptoms and signs of intracranial spread in addition to tinnitus and deafness (1). Otoscopy results can be misleading. The meso-tympanic mass, the margins of which are visible at 3600, can be identified as a glomus tympanicum tumour. If the margins cannot be clearly identified, during otoscopy, the tumour must be assumed to be a glomus jugulare until proven otherwise. A myringotomy and biopsy are to be usually avoided (2). To formulate an effective treatment plan, the radiologist has to provide information regarding the site (jugulare or tympanicum), and the extent and vascularity of the tumour (2). This information is essential for the surgeon since a glomus tympanicum can be removed via the transtympanic route, while a glomus jugulare needs an extensive skull based surgery (1). The first and the most important assessment when a jugulo tympanic tumour is suspected is the state of the jugular fossa. A CT scan with thin sections of temporal bone detail is the best method for demonstrating the margins of the jugular fossa (3). An intact jugular fossa and the demonstration of a clear air boundary between the tumour mass and the jugular bulb helps immediately identify the lesion as a glomus tympanicum and almost excludes the existence of a glomus jugulare completely (1, 2). A CT scan can demonstrate a soft tissue mass in the middle ear and its position relative to patterns of bone destruction. CT also helps to identify the status of ossicles and helps the surgeon to define the bony landmarks. Once a glomus tympanicum is diagnosed, no further imaging is necessary. CT may not be totally reliable for assessing whether the tumour has arisen from the jugular fossa or from the middle ear in the following situations: a) When the tumour reaches the floor of the middle ear, soft tissue silhouetting and partial volume averaging of this thin irregular bone plate may make it difficult to assess whether it is intact (3). b) Obstruction of the eustachian tube by glomus tumours in the middle ear will result in fluid accumulation in the rest of the middle ear and mastoid. This fluid is indistinguishable from the tumour when seen on CT scans (3). GD MRI is useful in the above situations and also helps to assess the intracranial extension and the relation of the glomus jugulare to the regional neuro vascular anatomy (2, 3). Angiography is no longer mandatory, but it should be used for preoperative evaluation of selected cases when embolisation can assist the surgeon by reducing the blood supply to a large tumour (3). Small paraganglionomas in the middle ear cavity can be identified using otoscopy, but only a radiology examination will show whether the jugular bulb is involved. This assessment largely governs the surgical approach.
Differential Diagnosis List
Glomus tympanicum tumour.
Final Diagnosis
Glomus tympanicum tumour.
Case information
URL: https://www.eurorad.org/case/2151
DOI: 10.1594/EURORAD/CASE.2151
ISSN: 1563-4086