At the first follow-up visit you discuss the pathology report with the patient, which reads as follows, “… sustentacular cell density and the immunohistochemical staining with S-100 and chromogranin of the chief cells in this tumor was very low.”

• Tumors arising from the jugular foramen are most likely glomus jugulare (paraganglioma).
  
• Other common possible lesions in the differential diagnosis include schwannoma and meningioma.
  
• Other surrounding tumors may invade into the jugular foramen. These constitute chordoma, chondrosarcoma, giant-cell tumor, cholesterol granuloma, endolymphatic sac tumor, temporal bone carcinomas, metastases, etc.1

• Other relevant studies would include an angiogram; CT scan of the head; and CT scans of the chest, abdomen, and pelvis.
  
• Serum and urine catecholamine levels and urine vanillylmandelic acid levels.
  
• Glomus jugulare belongs to the neuroendocrine tumor family that includes other paragangliomas including pheochromocytoma.²

• Conversion of norepinephrine to epinephrine requires phenylethanolamine-N-methyl transferase (PNMT) that is present in the adrenal medulla. A very high serum epinephrine level raises the suspicion for pheochromocytoma. Glomus jugulare, when chemically active, generally produces norepinephrine.³
  
• The patient should undergo both α- and β-adrenergic blockade (e.g., phenoxybenzamine and propranolol) prior to embolization or surgery. Note: Do not initiate β-adrenergic blockade until α- blockage is partially established.²

• A left-sided external carotid angiogram showing tumor blush fed via the ascending pharyngeal artery. Other arteries that may feed the glomus tumor are the occipital artery, internal maxillary artery, and the vertebrobasilar system.

• Surgery, radiation therapy (RT), as well as radiosurgery have all been used for the treatment of glomus tumor.
  
• A 20-year actuarial survival of 94% and a 20-year actuarial disease-free survival of 77% are reported with RT.⁴
  
• The aim of radiosurgery is tumor control. It has no reported mortality and 2.1% recurrence rate, but the regression in tumor size is reported in a little less than one-third of the patients. It can be used for smaller recurrences and residuals. In comparison, surgical resection is reported to have 1.3% mortality, 3.1% recurrence rate along with 92.1% surgical control, and a gross total resection of tumor in 88.2%.5
  
• Similar surgical success is also reported for complex glomus jugulare tumors.⁶

• Because glomus tumor is a highly vascular tumor, preoperative embolization performed 3–5 days prior to the surgery prevents excessive bleeding in the operating room.
  
• Similarly, the patient should be started on α- and β-blockers for blood pressure control if the tumor is hormonally active.
  
• Intraoperative monitoring of cranial nerves (CNs) VII, IX, X, XI, and XII is recommended along with brainstem auditory-evoked response and somatosensory-evoked potentials.
  
• The relationship of the CNs to the jugular foramen and hence, the tumor, are vital to the risk of damage to these nerves. Generally the lower CNs are pushed medially by the tumor and are at less risk than CNs VII and IX that may be in the path of the approach to resection of the tumor.⁷

• An ipsilateral carotid body tumor can be addressed at the same setting with the neck dissection that is performed with the tumor resection from the temporal bone.
  
• If the patient has bilateral glomus tumors as is seen in ~10% of sporadic cases and as high as 25–55% or more in familial cases, the resection on the opposite site should be performed only if the surgical resection on one side did not cause lower CN deficit.⁶

• Sustentacular cell density and the intensity of immunohistochemical staining of the chief and sustentacular cells are inversely proportional to the tumor aggressiveness.⁸
  
• Anaplastic or metastasizing paragangliomas are either devoid or very depleted of sustentacular cells.⁹

• Embryologically, glomus jugulare tumor is of neuro-ectodermal origin. Genes for this tumor are located on chromosome 11q^23.1 and 11q^13.1. The germline mutation is in succinate dehydrogenase subunits of mitochondrial enzyme system transmitted in an autosomal dominant inheritance pattern with variable penetrance only from the father.
  
• The responsible gene from an affected mother is inactivated but may become active in the subsequent generations if one of her sons gets the gene in question.³

• There are two well-recognized classification systems, summarized in Table 25.1.²

• Vernet syndrome affects CNs IX, X, and XI and is due to an intracranial lesion.
  
• Collet–Sicard syndrome affects CNs IX, X, XI, and XII and is usually due to an extracranial lesion.
  
• Villaret syndrome affects CNs IX, X, XI, XII, and the sympathetic nervous system and is usually due to a posterior retropharyngeal lesion.
  
• Jackson syndrome affects CNs X, XI, and XII and is usually due to a vascular infarction of the medullary tegmentum.
  
• Tapia syndrome affects CNs X, XII, and possibly IX and is usually due to a high cervical lesion.
  
• See Fig. 25.3 for further illustration.^10,11