Paragangliomas, also called glomus tumours, are neuroendocrine neoplasm’s composed largely of paraganglion chief cells (Burger and Scheithauer 2007). These tumours arise from glomus bodies also named paraganglia. A paraganglion possesses unique regulatory function and is part of the extra adrenal neuroendocrine system. Normal paraganglia occur in the head and neck region at several places (Table 5), frequently located near nerves and vessels (Petrus and Lo 1992; Rao et al. 1999; Lowenheim et al. 2006). Within the jugular foramen, the paraganglioma can arise from paraganglia located in the adventitia of the jugular bulb or at Jacobson’s nerve (nerve IX) or at Arnold’s nerve (nerve X). In the middle ear normal paraganglia are found at the cochlear promontory. Of all paragangliomas, 80 % are either glomus jugulare tumours or carotid body tumours (Lowenheim et al. 2006). Glomus jugular tumours are not encapsulated and tend to infiltrate connective tissue planes (Vogl and Bisdas 2009).

Paragangliomas restricted to the middle ear are called glomus tympanicum tumours. Glomus jugulotympanicum and glomus jugulare tumours involve, respectively, the middle ear plus the jugular foramen or the jugular foramen alone. Endocrinological functional activity is rare in head and neck paragangliomas, 93 % of the functioning tumours are pheochromocytomas (also a tumour of paraganglionic tissue) and only 7 % occurs at other sites (Maffe et al. 2000).

Paragangliomas may be multiple, either synchronously or metachronously in 3 % for sporadic cases to 26 % for the familial cases (Fig. 5). They can occur in association with pheochromocytoma, thyroid carcinoma, Carney triad (gastric leiomyosarcoma, pulmonary chondroma and paraganglioma) and other endocrine disorders. Familial paragangliomas have a prevalence of 7–9 %, with 90 % of the cases arising from the carotid body (Rao et al. 1999).

The symptoms depend on the primary site of origin and the extension of the tumour and include: a vascular tympanic membrane, conductive hearing loss, pulsatile tinnitus, bruit, vertigo, sensorineural hearing loss, cranial nerve deficit.

Paragangliomas are benign, but local invasive and very vascular tumours. From its origin in the middle ear, the glomus tympanicum first invades the bone between the hypotympanum and the jugular foramen. With further growth they are indistinguishable from a glomus jugulare, hence the term glomus jugulotympanicum. The differentiation between a simple glomus tympanicum and a glomus jugulotympanicum is an important radiological task, because there is a big difference in the operative approach, with the latter requiring extensive skull base surgery. From the jugular foramen the tumour can extend laterally with destruction of the mastoid segment of the facial canal and invasion of the facial nerve. Anteriorly, the tumour grows into the total middle ear and further along the petrous bone to the foramen lacerum and the cavernous sinus. Inferior spread produces infiltration of the internal jugular vein and further growth in the carotid loge below the skull base. The intracranial extension is first situated extra-axial in the cerebellopontine angle and in advanced cases not only extra-axial, but also intra-axial in the cerebellum. Glomus vagale tumours, arising from the ganglion nodosum or extravagal, may secondary extend into the jugular foramen.

The neuroradiological evaluation requires both CT and MRI (Table 7). Thin section CT in the axial and coronal plane with bone window gives information about the surrounding bony structures, such as the enlargement and erosion of the jugular foramen, the infiltration of the petrous bone, the carotid canal, the facial canal, the hypoglossal canal and the inner ear structures. It also helps in the differential diagnosis with lesions that do not erode the bone like schwannoma, meningioma (Fig. 6). MR shows the soft tissue extension of the tumour in the ear and below the skull base and intracranially (Fig. 7). MR is equally important in the differential diagnosis by showing the characteristic intratumoral vessels (signal void) and the frequent presence of subacute intratumoral haemorrhage with a high signal in the T1W and T2W image. The combination of both features gives a salt and pepper appearance in the T1W images without contrast. This feature is limited to the larger paragangliomas (>1 cm) and is not pathognomonic, as it is also seen in other hypervascular lesions like metastasis. Use of contrast is necessary to find the smaller tumours like the glomus tympanicum and for the demonstration of the soft tissue extent in the larger tumours. All paragangliomas have a strong enhancement. MR venography provides information about the jugular vein occlusion and collateral venous drainage. Two hallmarks of this tumour are the bony erosion and the rich vascularisation (Fig. 6). The latter poses special problems of blood loss during operation. Preoperative embolisation is needed in the larger tumours (see the chapter on the vascular lesion of the temporal bone).