Fig. 11.1
Otoendoscopic appearance of temporal bone paragangliomas. (a) Tympanic paraganglioma, (b) jugular paraganglioma, (c) facial paraganglioma
A comprehensive diagnostic workup is necessary in the evaluation of a temporal bone paraganglioma. Primarily, audiologic testing should be performed to objectively assess hearing. Conductive hearing losses are commonly seen, with an average preoperative air-bone gap of approximately 18 dB [25]. Sensorineural hearing loss is generally rare, though more extensive tumors can occasionally erode into the otic capsule. To fully assess the extent of disease and the structures affected by tumor growth, diagnostic imaging is of paramount importance. Historically, angiography and venography with polytomography were routinely used for diagnostic purposes [27]. In most cases involving temporal bone tumors, these modalities have largely been replaced in favor of computed tomography (CT) and magnetic resonance imaging (MRI) (Fig. 11.2). The performance of a contrast-enhanced, high-resolution CT scan of the temporal bone affords visualization of the bony erosion associated with tumor development, which can be helpful to distinguish lesions arising from the jugular bulb from those primarily within the middle ear. Specifically, preservation of the bony floor of the hypotympanum and jugulotympanic spine suggests the diagnosis of TP over JP. Furthermore, with regard to tumor expansion, an assessment of the osseous boundaries surrounding the inner ear, facial nerve, temporomandibular joint, intracranial space, and great vessels can help with surgical planning and patient counseling. It is also valuable to note that different lesions can mimic temporal bone paraganglioma on clinical assessment, and imaging can be helpful to distinguish between potential pathologies [25]. To this end, MRI can be a valuable adjunct to CT when considering the characteristic radiologic appearance of a paraganglioma. While CT cannot readily distinguish the density of a tumor mass within the temporal bone, a high-resolution MRI with and without contrast demonstrates the enhancement expected of this vascular tumor along with the flow voids that produce a “salt and pepper” appearance. While small TP tumors confined to the middle ear space may not always require an MRI for further characterization, this test can be particularly helpful to distinguish a larger tumor from trapped effusions within the temporal bone and to assess the presence of synchronous disease in the neck. Generally, a CT of the temporal bone and neck with and without contrast can be the primary evaluation of a patient presenting with clinical signs of a TP. If ambiguity remains, an MRI with and without contrast can provide further clarity as to the extent of disease locally and regionally.
Fig. 11.2
Radiographic comparison of skull base paragangliomas using computed tomography. (a) Tympanic paraganglioma tumor, (b) jugular paraganglioma tumor, (c) facial paraganglioma tumor, and (d) vagal paraganglioma tumor
The contemporary surgeon should consider secreting tumors and genetic predispositions to tumor development in the initial evaluation of a patient with a tympanic or jugular paraganglioma. As discussed above, certain symptoms at presentation should raise suspicion for a tumor with neurosecretory function. When these symptoms are present, analysis of serum and urine for catecholamines and catecholamine by-products is warranted. The use of ipsilateral jugular venous sampling is no longer encouraged for routine evaluation. With regard to genetic evaluation, patients with multiple paraganglioma neoplasms, with a paraganglioma tumor before 40 years of age, and with a clear family history of paraganglioma development may benefit from genetic screening [28]. In addition to the value of genetic counseling when a familial predisposition exists, genotyping may also be relevant to the potential for malignant transformation in existing tumors [22]. Knowing the wide variety of genetic aberrations that can be relevant to paraganglioma, one potential algorithm for a genetic workup suggested by Neumann et al. in 2009 includes an initial evaluation of loci relevant to SDHD and SDHB [29].
One of the final steps in TP evaluation is tumor staging. Many different classification systems have been proposed for TP, though two have historically predominated: Fisch-Mattox [30] and Glasscock-Jackson (Table 11.1) [31]. The most notable difference between the two systems is found in their handling of tympanic and jugular paraganglioma tumors. When using the Fisch-Mattox scale, tympanic and jugular paraganglioma are on one disease spectrum, while Glasscock-Jackson has separate staging tools for either tumor. At present, the most relevant use of the staging systems may lie in the determination of an appropriate surgical approach to use when planning treatment, as discussed below.
Table 11.1
The Glasscock-Jackson staging system for tympanic paraganglioma
Stage | Definition |
|---|---|
I | All tumor margins visible on otoscopy |
II | Tumor fills the middle ear, and margins are not visible |
III | Tumor extends into the mastoid air cells |
IV | Tumor erodes through the tympanic membrane and/or the bone of the external auditory canal |
Treatment and Prognosis
Surgery remains the gold standard for the management of TP. In most cases, complete tumor excision and symptom relief are achievable. However, before proceeding to the operating room, preoperative surgical planning is absolutely necessary. Given the vascular nature of these tumors, surgery can be particularly bloody. Preoperative angiography with embolization is most commonly discussed in the context of jugular paraganglioma; however, embolization of advanced stage TP may also be considered. While intraoperative bleeding during TP excision is not expected to cause hemodynamic instability, the anesthesia team should be aware of the potential for blood loss beyond what is generally seen with chronic ear surgery. Furthermore, as with any otologic case, aggressive management of intraoperative hypertension and tachycardia may help to lessen the degree of bleeding seen while handling inflamed tissue. Facial nerve monitoring should be considered in every TP surgery, due to the probability that tumor bleeding could obscure visualization within the middle ear. In cases that involve a tumor with neurosecretory function, the surgical and anesthesia teams must be prepared for the consequences of tumor manipulation. With the assistance of an endocrinologist, perioperative pharmacologic therapy can be sought to prevent an adrenergic crisis, particularly in patients who habitually use alpha- or beta-blocker drugs [32].
The most appropriate surgical approach to a TP is dictated by the size and extent of the tumor. When considering the Glasscock-Jackson staging system , transcanal excision can be considered to address stage I disease. Atticotomy and hypotympanotomy, respectively, can also be used to address disease that extends superiorly into the attic or inferiorly into the hypotympanum [33]. With stage II–IV disease, a postauricular incision is generally performed. With exposure to the mastoid cortex, a mastoidectomy and a posterior tympanotomy can be used for additional visualization of tumor margins. In some cases, the performance of an extended facial recess can be necessary to resect inferior extension of a tumor [34]. For class IV disease with extensive ear canal erosion, a modified radical mastoidectomy can be used to ensure complete tumor extirpation. In cases where advanced sensorineural hearing loss exists preoperatively, a subtotal petrosectomy with blind-sac canal closure is considered [25].
With contemporary microsurgical techniques, total resection can generally be expected, with contemporary series reporting tumor control rates approaching 100%. In anticipation of tumor bleeding, surgeons should be prepared with substrates such as cotton and Gelfoam® (Pfizer, New York) soaked in thrombin. Bone wax can also be useful when seeking to control bleeding arising from vessels within the bone of the middle ear. Additionally, the use of a laser or micro bipolar cautery often helps to achieve timely hemostasis during tumor dissection [35–37]. Dissection initially focuses on determining the tumor extent as well as the relationship of the tumor to the ossicles, the facial nerve, the tympanic membrane, the great vessels, and the inner ear. If a tumor is found to be densely adherent to one of these structures, attention should initially focus on freeing the other parts of the tumor before ultimately returning to the problematic area. Once the tumor has successfully been freed from its attachments, the location of the major vascular supply can be determined, and this vessel, frequently a derivative of the ascending pharyngeal artery, can be managed with cautery, laser, or bone wax [38]. The tumor is then avulsed from the middle ear cavity. Tympanoplasty, canal reconstruction, and/or ossicular reconstruction may be necessary prior to termination of the case. Rarely, tumors cannot be readily separated from important structures in the middle ear or mastoid, such as the facial nerve, or petrous carotid. In this situation, it is generally advocated that a subtotal resection be performed, leaving the tumor adherent to the vital structure in order to avoid unnecessary morbidity. Following a subtotal resection, clinical and radiographic disease observation can be utilized to monitor tumor growth, which is not assured [25].
In some cases, alternatives to surgical management must be pursued due to patient comorbidities. Not every patient with a TP tumor can withstand general anesthesia. In such a situation, clinical and radiographic tumor observation is an option, and patients should be counseled as to the potential for disease progression and the consequences associated with tumor bleeding in the ear canal as well as acquired dysfunction of the facial nerve and inner ear. However, even with large tumors, the incidence of the latter is relatively rare [25]. Since the great majority of TP can be removed safely with minimal morbidity and result in symptomatic improvement, radiosurgery is generally reserved for those that cannot tolerate surgical excision and have growing tumors [39, 40].
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