Paragangliomas are unusual tumors of the head and neck but should be included in the differential diagnosis of lateral neck masses. Although malignant paragangliomas are possible, these tumors are usually benign. Nevertheless, treatment can lead to great morbidity and possible mortality. The article by Drs. Hu and Persky addresses a multidisciplinary approach to these lesions.
Sites of Origin
Paragangliomas are highly vascular tumors of neural crest cell origin, as described by these authors and others. They most commonly arise from the carotid bifurcation and less commonly from the vagus nerve (vagal paragangliomas). Other sites include the ear, temporal bone, and skull base.
Traditional treatment involves surgical extirpation, which is associated with great morbidity, such as bleeding, stroke, and cranial neuropathies. The authors advocate a multidisciplinary approach to the management of these tumors, based on primary radiotherapy. However, controversies exist regarding the diagnostic work up, definitive management, and need for any adjuvant treatment.
Controversies in the Diagnostic Work-up
Whereas some surgeons do not recommend preoperative embolization, others highly recommend it. Because these tumors are extremely vascular, embolization performed by radiology colleagues can diminish blood loss during surgery. However, two caveats exist for preoperative embolization: First, the materials used for embolization can cause a reaction in local tissue, resulting in adhesions and loss of tissue planes and making surgical resection difficult. There could also be a paradoxical increase in loss of blood volume and violation of major arteries, such as the carotid artery. Second, the surgery must follow the embolization in a timely fashion so that the emoblizing effects have not diminished.
Because the majority of paragangliomas of the head and neck reside at the carotid bulb, some surgeons advocate routine evaluation of the cerebral circulation. The reliability of carotid occlusion tests in predicting neurologic sequelae has been confirmed.[1-3] Concurrent use of nuclear medicine imaging of brain activity while occluding the carotid has been reported to increase its reliability.[1-3]
As stated by the authors, surgical management remains the mainstay of treatment. However, paragangliomas located in inaccessible or difficult sites such as the skull base and temporal bone may not be resectable. The role of radiosurgery has been explored in this article, and it remains a promising technique. However, its role may be limited to large tumors, particularly those that are diffusely spreading. Stereotactic radiosurgery may limit the morbidity associated with cranial neuropathies, but it may result in incomplete resection, especially of large tumors.
Paragangliomas have been traditionally regarded as radioresistant tumors, but De Jong et al described the use of radiation for middle ear paragangliomas. In their retrospective series of 38 patients with temporal bone paragangliomas (1956-1991), the authors described local control rates of 79% in the primary radiation group, 100% in the combined-treatment group, and 91% in the salvage therapy group. With the advent of conformal irradiation and new dosing techniques, they rekindled the use of radiation as definitive treatment of paragangliomas in the head and neck.
Hu and Persky argue that radiation should not be relegated to palliative treatment in patients with unresectable disease or with major medical comorbidity. However, their conclusion that surgical resection and primary radiotherapy result in equivalent cure rates may be flawed because of the use of retrospective data. The authors also discuss the use of radiation in the adjuvant setting, but advocate primary radiation because of the decreased morbidity and equivalent tumor control rate associated with the treatment.
It is agreed that the treatment of paragangliomas of the head and neck should be dictated by the efficacy and morbidity of the treatment modality. Large-scale prospective trials are not realistic or practical for a disease with such a low incidence. Drs. Hu and Persky advocate radiation as primary treatment based on the retrospective studies outlined. A better method of evaluating these studies in the future would be to perform a meta-analysis, which could result in better evidencebased medicine because of efforts to stratify the different variables of the studies and come to meaningful conclusions. Also, a quality-of-life and/or functional status study may be useful for comparing outcomes in patients treated with radiation vs surgery.