Paragangliomas of the head and neck Pictorial review Paragangliomas of the head and neck Al hashem a., al jubeilan r., kristjansson s., nicolas-jilwan m. Department of Radiology, Neuroradiology Division King Faisal Specialist Hospital & Research Center Riyadh, Saudia Arabia

Disclosure Nothing to disclose

INTRODUCTION Paragangliomas are rare neuroendocrine tumors arising from the paraganglionic cells scattered throughout the body. Also referred to as glomus tumors or chemodectomas. Paragangliomas of the head and neck represent less than 1% of head and neck tumors. They occur at predictable locations in the head & neck, most commonly from the carotid body at the carotid bifurcation, along the vagus nerve, in the jugular foramen and in the tympanic cavity. Can be bilateral or multicentric (synchronous or metachronous), in particular in familial cases. Malignant behavior with metastasis seen in 2-13% of cases.

Characteristic Imaging features A carotid body paraganglioma splays the carotid bifurcation. A vagal nerve paraganglioma most commonly arises from the inferior nodose ganglion, compresses the internal jugular vein, displaces the internal and external carotid arteries anteromedially, and the lateral laryngeal wall medially. Glomus tympanicum paragangliomas occur in the middle ear along the Jacobson nerve at the cochlear promontory. Glomus jugulare tumors arise within the jugular foramen from the jugular bulb, Jacobson nerve or Arnold nerve. 3 characteristic features of glomus jugulare spread pattern: Moth-eaten pattern of destruction of the temporal bone. Propensity for erosion of the inferior tympanic cavity wall and extension into the middle ear cavity: glomus jugulotympanicum. Intracranial extension in the posterior fossa and extracranial extension in the carotid space.

Characteristic Imaging features Highly vascular strongly enhancing tumors. In tumors larger than 1 cm, vascular flow voids can be identified, potentially giving a salt (foci of hemorrhage, slow flow) and pepper (flow voids) appearance on MRI. Angiography demonstrates enlarged feeding arteries (most commonly the ascending pharyngeal artery and ascending cervical artery), intense tumoral blush, and early draining veins. Indium 111 Octreotide is the nuclear medicine agent of choice for imaging paragangliomas. They characteristically show early intense uptake. Octreotide scans are most sensitive for tumors larger than 1.5cm. MIBG (metaiodobenzoguanidine) scans are less sensitive and less specific.

Shamblin classification of carotid body tumors (1971) Type 1 : Splays ICA and ECA Type 2: Splays ICA and ECA with partial encasement Type 3: Splays ICA and ECA with full encasement .

PURPOSE OF OUR REVIEW Highlight the distinstive imaging features of paragangliomas on a wide range of imaging modalities. Emphasize the tendency of these tumors for bilaterality and multiplicity as well as the risk of malignant behavior and metastasis.

MATERIALS & METHODS 9 (8 of which pathologically proven) cases of head & neck paragangliomas are reviewed, patients aged 29 to 75 years old, encompassing the full spectrum of this disease: carotid body tumors, glomus vagale tumors, glomus jugulare tumors, glomus tympanicum tumors as well as bilateral, multifocal and metastatic conditions. The imaging modalities performed included contrast enhanced CT, contrast enhanced MRI, nuclear medicine studies and conventional angiography.

CASE 1 43 year old female with left carotid body paraganglioma metastatic to the lungs and L2 vertebral body

MRI of the primary tumor: Axial and coronal postcontrast T1 Large avidly enhancing mass which splays the external carotid artery (green arrow) and internal carotid artery (yellow arrow). Note the vascularity of the tumor with internal flow voids (red arrow) .

ANTERIOR POSTERIOR ANTERIOR POSTERIOR 3 hours Octreotide scan Characteristic intense uptake of the primary tumor on early 3 hours Octreotide scan (yellow arrow). Also note uptake of lung metastasis (pink arrows) and a tiny focus of uptake in the L2 vertebra (green arrow).

MIBG scan (top row) and PET scan (bottom row) confirm L2 metastasis (red marker) and lung metastasis (not shown). MIBG scans are less sensitive and less specific than Octreotide scans.

Sagittal postcontrast MRI of the lumbar spine confirms an enhancing L2 vertebral body lesion (green arrow).

CASE 2 75 year old female with left carotid body paraganglioma

Sagittal and axial images from neck CTA Large avidly enhancing mass which splays the external carotid artery (green arrow) and internal carotid artery (yellow arrow).

CASE 3 48 year old male with right carotid body paraganglioma metastatic to the liver, lungs, and bone & multifocal with additional tumor at the right common carotid artery (glomus vagale tumor) The primary carotid body tumor was embolized with PVA particles and resected.

Axial T1 postcontrast with fat saturation Neck CTA Large avidly enhancing mass which splays and encases the external carotid artery (green arrow) and internal carotid artery (yellow arrow). Type III tumor according to the classification of Shamblin.

MRA (LEFT) and conventional angiogram (RIGHT) demonstrate high tumor vascularity and tumor blush on angiogram (GREEEN ARROWS).

Additional avidly enhancing tumor along the right common carotid artery (green arrow), illustrates the tendency for multifocality of these tumors.

Contrast enhanced CT abdomen & pelvis Axial images demonstrate hypervascular hepatic metastasis (some indicated by the yellow arrows) Sagittal images show multilevel bony metastasis to the spine (some indicated by the green arrows).

CASE 4 65 years old female, right carotid body paraganglioma Shamblin type I, completely resected

Sagittal and axial images from neck CT Large avidly enhancing mass which splays the external carotid artery (green arrow) and internal carotid artery (yellow arrow) without encasement.

CASE 5 29 years old with bilateral & multifocal paragangliomas compatible with glomus vagale tumors .

Coronal and axial images from contrast enhanced neck CT Large avidly enhancing bilateral upper cervical masses displace the carotid arteries anteromedially and splay the internal jugular vein from the carotid arteries, a pattern compatible with glomus vagale. The coronal image demonstrates an additional tumor along the left lower cervical vagus nerve (pink arrow).

Coronal T2 with fat saturation demonstrates the high tumor vascularity with multiple flow voids within all 3 tumors.

ANTERIOR POSTERIOR ANTERIOR POSTERIOR Octreotide scan demonstrates uptake of all three tumors (pink arrows) without evidence of additional tumors or metastatic disease.

CASE 6 54 year old male with right glomus jugulare tumor.

Contrast enhanced CT: Large enhancing tumor centered at the jugular foramen, with typical pattern of permeative bone destruction (pink arrows) and classical pattern of extension at the cerebellopontine angle and along the carotid space

Axial T2 and postcontrast axial T1 demonstrate an avidly enhancing very vascular tumor with multiple vascular flow voids (pink arrow).

CASE 7 39 year old female with bilateral carotid body tumors, left glomus vagale and hepatic metastasis.

Contrast enhanced neck CT shows a type III right carotid body tumor (yellow star) that encases right internal and external carotid arteries and a type I left carotid body tumor (pink star) that splays the left internal and external carotid arteries without encasement. MRA also demonstrates a large left glomus vagale tumor .

Reconstructed MIP image from PET CT demonstrates intense uptake of the three tumors (marked by stars).

CASE 8 56 year old male presented with right ear tinnitus Right glomus tympanicum

Classical finding of an avidly enhancing small middle ear tumor at the cochlear promontory (pink arrow).

2 years followup after radiosurgery treatment Significant improvement with minimal persistent enhancement (pink arrow).

CASE 9 60 year old female with right glomus tympanicum

CT TEMPORAL BONES CLASSICAL SOFT TISSUE MASS IN THE RIGHT MIDDLE EAR ALONG THE COCHLEAR PROMONTORY (PINK ARROW)

CANAL WALL DOWN MASTOIDECTOMY WAS PERFORMED TUMOR WAS RESECTED CANAL WALL DOWN MASTOIDECTOMY WAS PERFORMED

Key points All head & neck paragangliomas LOCATION KEY IMAGING FEATURES CAROTID BODY Splays internal and external carotid arteries Shamblin classification correlates with surgical outcome (worst for type III) GLOMUS VAGALE Displaces carotid arteries anteromedially and splays internal jugular vein from carotid arteries. GLOMUS JUGULARE Permeative destruction at the skull base Extension to the right cerebellopontine angle and along the right carotid space Erosion into the middle ear cavity (glomus jugulotympanicum) GLOMUS TYMPANICUM Small avidly enhancing middle ear tumor at the cochlear promontory All head & neck paragangliomas Avidly enhancing and highly vascular Tendency for bilaterality and multifocality Risk of metastasis High uptake on Octreotide scan, MIBG scan and PET scans.

REFERENCES Rao AB, Koeller KK, Adair CF. From the archives of the AFIP. Paragangliomas of the head and neck: radiologic-pathologic correlation. Armed Forces Institute of Pathology. Radiographics. 1999 Nov-Dec;19(6):1605-32.

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