eRadiograph Volume 7: Imaging of Oral Cavity | Page 266
Glomus jugulare
These tumors originate in the jugular foramen – typically presenting with otologic
symptoms such as pulsatile tinnitus, conductive hearing loss or aural fullness, or cranial
nerve palsies of IX to X1. These appear as soft tissue masses which tend to cause bony
erosion/destruction which is best demonstrated on CT scans. On CT these masses
appear as enhancing mass lesions in the jugular fossa, these may extend intra or
extracranially. This extent is best defined with a MRI study. On MRI they appear as soft
tissue mass lesions with a salt and pepper appearance on T1 weighted images. The
white components representing salt is slow flow in the vessels and the dark or pepper
component is high flow in the vascular component. Posterior extension of the lesion
may erode petrous bone and mastoids. On angiography a feeder artery with an arterial
blush is usually seen from external carotid circulation usually the ascending
pharyngeal. There may be evidence of venous compression or invasion of the internal
jugular vein. Small glomus jugulare tumors are treated with surgery, larger and more
extensive glomus jugulare are treated by radiotherapy.
A glomus tumor restricted to the middle ear is termed as a glomus tympanicum.
Neurofibromas
These are less common neurogenic tumors found in the carotid space – 50% of these
are associated with NFI, 50% are sporadic. Multiple neurofibromas are seen in the
setting of NFI neurofibromas are hyperintense on T2W1 and enhance densely after
administration of contrast. It is difficult to distinguish neurofibroma from
Schwannoma on imaging. Plexiform neurofibroma are poorly marginated lesions
arising from nerve trunks with multiple branches involved. These are difficult to resect
surgically.
Malignant Lesions
Malignant lesions in the carotid space are usually as a result of extracapsular spread of
deep parajugular metastatic lymph nodes. This is as lymph nodes are not present in
the carotid sheath. The nodal mass is usually ill defined with central necrosis,
obliteration of fat plane between nodal mass and carotid artery indicates local
infiltration into the carotid space. Malignant neoplasms from the oral cavity, adjacent
spaces may extend into the carotid space encasing the carotid vessels.
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Carotid Space
Neurogenic Tumors
Schwannomas are the most common solitary neurogenic tumor of the head and neck
– these may arise from any of the nerves in the carotid sheath namely the
glossopharyngeal, vagus, accessory, hypoglossal or sympathetic chain. Similar to
Paraganglionomas, schwannomas of the vagal nerve displace the carotid artery
anteromedial and sympathetic chain displace the carotid artery anterolaterally. On
imaging they appear as homogenous enhancing mass lesions though they may
demonstrate cystic degeneration which will be seen as T2 hyper intense and non
enhancing components.