Paragangliomas are tumors that arise from the paraganglionic system—aggregations of cells found throughout the body associated with vascular and neuronal adventitia. They originate from the neural crest and are related to the autonomic nervous system.

Temporal bone paragangliomas (TBPs) arise either in the adventitia of the jugular bulb or along the course of the Jacobson’s nerve (the tympanic branch of the glossopharyngeal nerve) or the Arnold’s nerve (the auricular branch of the vagus nerve). The term tympanicum has been applied to those paragangliomas arising on the promontory and remaining confined to the middle ear and mastoid compartments, without erosion of the jugular plate and involvement of the jugular bulb. Jugular paragangliomas have been described as those arising from within the jugular bulb. The exact site of origin is often difficult to determine because paragangliomas can arise from within the canaliculi of the temporal bone, the jugular fossa, and the middle ear cleft, which are in close proximity to each other.

Vagal paragangliomas arise from the nodose ganglion in almost all cases.

Carotid body tumors originate from the carotid body at the carotid bifurcation.

Paragangliomas of the head and neck make up only 3% of all paragangliomas, comprising approximately 0.6% of head and neck tumors and 0.03% of all tumors. The overall incidence of head and neck paraganglioma ranges from 1 in 30,000 to 1 in 100,000, with carotid body tumors making up nearly 60% of head and neck paragangliomas, tympanojugular paragangliomas (TJPs) nearly 40%, and vagal paragangliomas < 5%. The fact that carotid body tumors are far more common than other head and neck paragangliomas is probably due to a higher mass of normal paraganglionic tissue in this area. Carotid body tumors and vagal paragangliomas can be grouped clinically as cervicocarotid tumors.

TJPs constitute the second commonest tumor of the temporal bone and the commonest tumor affecting the jugular fossa. Tympanic paragangliomas are the commonest neoplasm affecting the middle ear. Thus, while rare, these are lesions that are frequently encountered by the skull base and head and neck surgeon.

Paragangliomas can arise both as sporadic and as familial entities, a fact first documented in 1933 by Chase, in a description of bilateral carotid body tumors in sisters. It is now known that 25 to 35% of paragangliomas are associated with recognized genetic defects, most of which are due to hereditary transmission. These defects are usually associated with one of the four familial paraganglioma syndromes. This means that approximately 30% of apparently sporadic head and neck paragangliomas are due to one of these defects. Multiple tumors are not uncommon, found in 10 to 20% of sporadic cases and in up to 80% of familial cases.

All subtypes of head and neck paraganglioma show a peak age of presentation in the fourth and fifth decades, with rare incidences of pediatric cases. While the sex ratio is equal for carotid body tumors, females are affected four to six times more than males in TJPs. However, males are more commonly affected in the familial type. All patients with a familial etiology present at a significantly younger age.

Paragangliomas are predominantly benign, slow-growing, highly vascular tumors, but they have a propensity for aggressive local destruction. Due to this clinical behavior, they have the ability to cause significant morbidity, especially when arising in relationship to the skull base with its multitude of associated neurovascular structures.

Because of their generally slow growth and initial absence of symptoms, TJPs are often not detected until they are of significant size. Those arising initially in the tympanic cavity, however, are usually detected at an earlier stage due to the presentation with hearing loss from ossicular chain interference and/or with pulsatile tinnitus. With progression, TJPs most frequently follow a path of least resistance into the middle ear cleft and within the jugular vein. Further spread then occurs through air cell tracts to involve the intrapetrous carotid canal, along the Eustachian tube, into the neck along the carotid sheath, and, in later stages, intracranially. The tumor can also extend along the inferior petrosal sinus. Intracranial spread usually occurs through the medial wall of the jugular foramen. Lower cranial nerve (LCN) involvement occurs later and is usually related to invasion through the medial wall of the jugular bulb. The facial nerve lies in close proximity to the jugular bulb in its vertical segment and is also at risk.

Whether arising in the middle ear or from within the canaliculi or bulb, the most common finding on examination is the presence of a vascular middle ear mass. The classically described blanching of the middle ear component, Brown’s sign, is present in 20%. Otoscopy alone is not reliable for assessing extent, most significantly in relation to the degree of hypotympanic extension. Tumors invading the tympanic bone from the jugular fossa can show the classic “rising sun” sign. Paragangliomas can also extend through the tympanic membrane and be confused with an inflammatory polyp, and occasionally otorrhagia can be a significant clinical symptom.

While a paraganglioma is the most common cause of a retrotympanic vascular mass, other pathology must be considered. Obviously, any vascular mass seen on otoscopy, if the margins are not seen in their entirety, involves the jugular bulb until proven otherwise.

A full cranial nerve examination is essential, including upper aerodigestive tract endoscopy and careful palpation of the neck. Silent LCN palsies are present in approximately 10% of patients.

11.1 Clinical Presentation of Tympanic and Tympanomastoid Paragangliomas

Paragangliomas arising in and remaining within the middle ear and mastoid system are termed tympanic and tympanomastoid paragangliomas. In general terms, they are a subtype of TJPs and correspond to the Fisch type A and B classification; they are seen significantly less commonly than are TJPs. These tumors usually present with conductive hearing loss and pulsatile tinnitus at a relatively early stage. They appear to behave in a less aggressive fashion than those arising from the jugular bulb. Interestingly, in our series no tympanic paragangliomas were associated with multiple tumors or with a genetic predisposition.

These tumors are usually otoscopically visible as retrotympanic reddish masses, determination of the degree of extension usually requiring imaging, most importantly to confirm that the jugular plate remains intact. Occasionally, visualization of the retrotympanic mass can be difficult, such as in the presence of tympanosclerosis. Very rarely, presentation is as a polyp occupying the external auditory canal. At presentation, approximately 20% of tympanic paragangliomas have extended to the mastoid air cells. Eustachian tube extension is not uncommon, also occurring in approximately 20% of cases. Ossicular chain involvement is found in around 50%. While rare, direct involvement of the carotid can occur, as can extension downward to invade the jugular bulb.

11.2 Clinical Presentation of Tympanojugular Paragangliomas

TJPs (previously glomus jugulare) are those tumors arising from the paraganglia of the adventitia of the jugular bulb or within the inferior tympanic or mastoid canaliculi. While the term tympanojugular paragangliomas can be used to describe both jugular and tympanic paragangliomas as a single group, those limited to the middle ear and mastoid are usually excluded, as discussed earlier. Treatment outcomes in relation to TJP are highly dependent on the stage of the tumor at diagnosis. A high index of suspicion is required along with the judicious use and review of constantly advancing radiological studies. Accordingly, the goal is to identify these tumors early and, in the age of genetic testing, to selectively use screening to identify presymptomatic lesions.

The most common presenting symptom of a TJP is hearing loss, present in approximately 60 to 80% of cases, with pulsatile tinnitus also affecting the majority of patients. Hearing loss is usually conductive in nature due to a combination of impingement of the ossicles and a middle ear effusion. Therefore, the diagnosis of a paraganglioma should be considered in any patient with pulsatile tinnitus, especially if it is associated with conductive hearing loss. It is important to note that, due to the nonspecific nature of these symptoms, there is an average 2 to 3 years’ delay between the onset of symptoms and diagnosis. Sensorineural hearing loss and/or vestibular symptoms depend on the invasion of the inner ear, internal auditory canal, or cerebellopontine angle, while LCN deficits usually develop as a consequence of the progressive invasion of the medial wall of the jugular fossa. Nerve deficits induced by tumor growth generally develop very slowly, allowing progressive compensation, so that the patient is sometimes unaware of the deficit itself. Silent LCN palsies are noted in around 10% of cases. Palsies of the glossopharyngeal and vagus nerves occur in approximately 35 to 40%, those of spinal accessory and hypoglossal nerves occurring in 21 to 30%. The facial nerve is the next most common cranial nerve involved at presentation, with involvement occurring in approximately 10% of TJPs, although it is reported to be as high as 39%. It is important to consider jugular fossa pathology when investigating an isolated, or compound, LCN lesion. Vocal fold paralysis presenting with a change in voice is the most common clinical scenario. Obviously, evidence of a high vagal lesion, such as palatal asymmetry, strongly suggests pathology at the skull base.

11.3 Imaging Characteristics

High-resolution computed tomography (HRCT), with reconstructions in axial and coronal planes, is mandatory in every suspected case of TJP. If jugular foramen involvement is suspected, T1-weighted (T1W), T2-weighted (T2W), and T1W gadolinium-enhanced sequences with axial, coronal, and sagittal plane reconstruction, along with magnetic resonance angiography (MRA) and magnetic resonance venography (MRV), are the minimum additional imaging studies required. Diagnostic four-vessel angiography is reserved for doubtful cases. The diagnosis of skull base pathology is based on radiological information, not on histopathology from biopsy specimens.

Tympanic paragangliomas appear on CT as small masses located on the surface of the promontory. In class B lesions, the tumor invades the hypotympanum without erosion of the jugular plate. Mastoid opacification is frequently related to fluid accumulation related to Eustachian tube obstruction.

11.3.1 Tympanojugular Paragangliomas

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  CT scan: On CT, TJPs show characteristic irregular bony erosion (moth-eaten bone). Early changes are represented as an indistinct lateral margin of the jugular fossa, followed by erosion of the caroticojugular crest or jugular spine. The degree of bony involvement is often difficult to assess, however. The most critical initial step is the differentiation between tympanomastoid paragangliomas and small TJPs, with a coronal image being the most helpful. If HRCT confirms that the lesion remains free of the jugular fossa, no further imaging is mandatory; magnetic resonance imaging (MRI) can be very helpful in differentiating tumor from middle ear and mastoid effusions. However, any doubt on any radiological view necessitates further assessment. The degree of bony infiltration can also be difficult to ascertain and it is often underestimated. This is especially the case in poorly pneumatized temporal bones and in the presence of involvement of the petrous apex, clivus, occipital condyle, and hypoglossal canal, because of the bony marrow usually present in these areas.

  
  
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  MRI: MRI provides exquisite detail relating to the soft-tissue relationships in the deep neck spaces as well as intracranially. Around 60 to 75% of cases have intracranial extension at presentation, with the rate of intradural involvement being approximately 30%. Several sequences can be employed to delineate both the tumor and arterial anatomy and venous drainage. Low to intermediate T1W signal and relatively high T2W signal are typical for paragangliomas. Small tumors enhance homogeneously, but areas of necrosis and hemorrhage are present with increasing size. A classic “salt and pepper” pattern in lesions larger than 2 cm (in any dimension) is often seen, especially in T2W images. This is due to areas of brightening on T2-weighting due to areas of slow flow within the tumor, and the presence of large intratumoral vasculature appearing as flow voids. Axial and coronal images are commonly used to evaluate the lesion, but sagittal images allow appreciation of tumor extension as a whole. Dural invasion is not always easy to detect because often the dura is infiltrated and pushed medially; in other instances, there is a true invasion of the posterior fossa. MRI affords information regarding invasion into the marrow spaces of the base of skull with effacement of the normal fatty signal. While each department often uses a different combination of sequences, no longer are only T1W, T2W, and contrast studies used. Dual T2 fast spin echo sequences, noncontrast and contrast time-of-flight sequences, and contrast-enhanced MRA and MRV (often with 3D reconstruction) provide further information. Despite these advances, detection of lesions less than 10 mm in size is difficult, except for those arising in the tympanic cavity.

  
  
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  Angiography: Angiography plays a critical role in the management of TJPs, but is rarely necessary for diagnosis. Paragangliomas display a characteristic intense tumor blush and rapid venous diffusion. This allows differentiation in cases where CT and MRI remain equivocal. Just as importantly, it allows detailed analysis of tumor vascular supply and embolization if operative management is planned, as well as assessment of internal carotid artery (ICA) involvement, contralateral cerebral blood flow, and venous drainage.

11.4 Classification: The Modified Fisch Classification System for TJP

Two classification systems are in common use for TJP, that of Fisch and that of Glasscock–Jackson. In terms of describing the involvement of the ICA, the most critical aspect in planning the surgical approach, we recommend use of the Fisch system. There is also a close correlation between Fisch class C and the likelihood of intracranial extension. We have made minor modifications to the Fisch classification to allow precise surgical planning. For this reason, as well as for consistency in reporting, we recommend that the modified Fisch system be used, as outlined in the following.

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  Class A: tumors limited to the middle ear cleft without invasion of the hypotympanum:

  
  
  
  
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    A1: tumor completely visible on otoscopic examination ( ▶ Fig. 11.1).

    
    
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    A2: tumor margins not seen on otoscopy ( ▶ Fig. 11.2).

  
  
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  Class B: limited to the hypotympanum, mesotympanum, and mastoid without erosion of jugular bulb:

  
  
  
  
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    B1: tumors confined to the middle ear cleft with extension to the hypotympanum ( ▶ Fig. 11.3).

    
    
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    B2: tumors involving the middle ear cleft with extension to the hypotympanum and the mastoid ( ▶ Fig. 11.4).

    
    
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    B3: tumors confined to the tympanomastoid compartment with erosion of the carotid canal ( ▶ Fig. 11.5).

  
  
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  Class C: TJP subclassification by degree of carotid canal erosion:

  
  
  
  
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    C1: tumors destroying the jugular foramen and bulb with limited involvement of the vertical portion of the carotid canal ( ▶ Fig. 11.6).

    
    
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    C2: Tumors invading the vertical portion of the carotid canal ( ▶ Fig. 11.7).

    
    
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    C3: Tumors invading the horizontal portion of the carotid canal ( ▶ Fig. 11.8).

    
    
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    C4: Tumors reaching the anterior foramen lacerum ( ▶ Fig. 11.9)

  
  
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  Class D: defines only the intracranial tumor extension and should be reported as an addendum to the C stage. De, extradural; Di, intradural.

  
  
  
  
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    De1: tumors with up to 2 cm dural displacement.

    
    
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    De2: tumors with more than 2 cm dural displacement.

    
    
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    Di1: tumors with up to 2 cm intradural extension.

    
    
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    Di2: tumors with more than 2 cm intradural extension.

    
    
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    Di3: tumors with inoperable intracranial intradural extension.

  
  
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  Class V: subclassification by degree of the vertebral artery involvement:

  
  
  
  
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    Ve: tumors engulfing the extradural vertebral artery ( ▶ Fig. 11.10).

    
    
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    Vi: tumors involving the intradural vertebral artery.

    
    
    
    

    

    
    

    Fig. 11.1 Class A1. Small tumor is clearly seen on the promontory (arrow). Tumor margins do not involve the annulus. (a) CT. (b) Schematic illustration. FN, facial nerve; ICA, internal carotid artery; JB, jugular bulb; SS, sigmoid sinus; T, tumor.

    
    
    
    

    

    
    

    Fig. 11.2 Class A2. Tumor margins (T) are not seen on otoscopy. (a) CT. (b) Schematic illustration. FN, facial nerve; ICA, internal carotid artery; JB, jugular bulb; SS, sigmoid sinus; T, tumor.

    
    
    
    

    

    
    

    Fig. 11.3 Class B1. Tumor (T) is limited to the middle ear cleft with extension to the hypotympanum but without erosion of the jugular bulb. (a) CT. (b) Schematic illustration. FN, facial nerve; ICA, internal carotid artery; JB, jugular bulb; SS, sigmoid sinus; T, tumor.

    
    
    
    

    

    
    

    Fig. 11.4 Class B2. Tumor (T) is occupying entire middle ear with extension to the hypotympanum and mastoid. Bony erosion of the promontory, fallopian canal, and ossicles can be noted. Arrow: no erosion of the carotid canal. (a) CT. (b) Schematic illustration. FN, facial nerve; ICA, internal carotid artery; JB, jugular bulb; SS, sigmoid sinus; T, tumor.

    
    
    
    

    

    
    

    Fig. 11.5 Class B3. Erosion of the carotid canal (arrow) can be seen on this slice. (a) CT. (b) Schematic illustration. FN, facial nerve; ICA, internal carotid artery; JB, jugular bulb; SS, sigmoid sinus; T, tumor.

    
    
    
    

    

    
    

    Fig. 11.6 (a) Class C1. Schematic illustration. AFL, anterior foramen lacerum; C1, atlas; CF, carotid foramen; CS, cavernous sinus; ICA, internal carotid artery; IJV, internal jugular vein; JF-CF, jugular foramen–carotid foramen; OC, occipital condyle; SS, sigmoid sinus; T, tumor; V, vertical portion of the internal carotid artery; VA, vertebral artery; VII, facial nerve; IX, glossopharyngeal nerve; X, vagus nerve; XI, spinal accessory nerve; XII, hypoglossal nerve. (b) Class C1 (CT). Note that tumor involvement can be seen in the jugular fossa, and erosion of the carotid foramen of the ICA (arrow). (c) Class C1 (CT). The horizontal portion of the carotid canal is not involved. (d) Class C1 (MRI). Tumor extending to but not eroding vertical portion of the carotid canal (arrow).

    
    
    
    

    

    
    

    Fig. 11.7 (a) Class C2. Schematic illustration. (b) Class C2. CT shows that the horizontal portion of the carotid canal is intact. (c) Class C2De1 (MRI). Tumor is engulfing the vertical portion of the carotid canal. (d) Class C2 (magnetic resonance angiography). Hypervascular area (arrow) can be seen lateral to the vertical portion of the carotid artery.

    
    
    
    

    

    
    

    Fig. 11.8 (a) Class C3. Schematic illustration. (b) Class C3De1 (CT). The erosion of the horizontal portion of the carotid canal is seen (arrow). (c) Class C3De2 (MRI). MRI shows clearly the involvement of the horizontal portion of the carotid canal and the sigmoid sinus. (d) Class C3Di2 (MRI). Large paraganglioma with intradural extension.

    
    
    
    

    

    
    

    Fig. 11.9 (a) Class C4. Schematic illustration. (b) Class C4 (CT). The tumor erodes all the temporal bone up to the petrous apex and the clivus, with total engulfment of the carotid artery and the cavernous sinus. (c) Class C4Di2 (MRI). MRI of the same case with clear involvement of all the horizontal portion of the carotid artery with extension to the cavernous sinus.

    
    
    
    

    

    
    

    Fig. 11.10 (a) Class V. Schematic illustration. (b) Class Ve (MRI). Extradural vertebral artery (black arrow) involved with the tumor.

11.5 Class A: Tympanic Paragangliomas

Class A type tumors have been shown in ▶ Fig. 11.11, ▶ Fig. 11.12, ▶ Fig. 11.13, ▶ Fig. 11.14, ▶ Fig. 11.15, ▶ Fig. 11.16, ▶ Fig. 11.17, ▶ Fig. 11.18, ▶ Fig. 11.19, ▶ Fig. 11.20, ▶ Fig. 11.21, ▶ Fig. 11.22.

11.5.1 Surgical Management

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  For class A1 tumors, a transcanal approach can be performed safely, as it gives good access to the entire tympanic membrane. When there is limited access due to anatomical variation, these cases are to be treated as class A2.

  
  
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  For class A2 tumors, a retroauricular transcanal approach is indicated. A modification of the traditional approach is used, removing the entire tympanomeatal flap. After removal of the tumor, myringoplasty is completed with fascia with replacement of the tympanomeatal flap (glove finger flap technique). This technique allows wider access to the tumor by drilling of the bony meatus.

The surgical management of Class A type tumors has been shown in ▶ Fig. 11.23, ▶ Fig. 11.24, ▶ Fig. 11.25, ▶ Fig. 11.26, ▶ Fig. 11.27, ▶ Fig. 11.28, ▶ Fig. 11.29, ▶ Fig. 11.30, ▶ Fig. 11.31, ▶ Fig. 11.32, ▶ Fig. 11.33, ▶ Fig. 11.34, ▶ Fig. 11.35.

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