Tympanojugular paragangliomas, also commonly known as glomus tympanicum tumors, are benign slow growing tumours. Because of its indolent nature, diagnosis is usually delayed until it reaches in significant size. They arise from rests of paragangliar tissue contained in the middle ear space. Although variations have been reported, these tumours most commonly arise from the dome of the jugular bulb: the tympanic branch of the gloss pharyngeal nerve (Jacobson’s nerve), the auricular branch of the vagus nerve (Arnold’s nerve) and a promontory mucosa. Paths of a spread of glomus jugulare tumours are predictable, following lines of a least resistance, including mastoid air cells tracts, vascular channels and jugular vein lumen, the Eustachian tube and neural foramina. The floor of the tympanic cavity is often destroyed by a superiorly spreading tumour, with a subsequent involvement of middle ear ossicles, destruction of the adjacent carotid crest and the jugular spine. Medial spread from the mesotympanum involves the cochlea; first, the tumour fills in intracochlear spaces, then causing osteonecrosis of the osseous labyrinth during a later stage.
The most common presenting symptom for TJPs is hearing loss that is present in approximately 60-80% of cases with many subjects also complaining about their pulsatile tinnitus. The other symptoms include hoarseness, dizziness, or dysphagia. Facial paresis is occasionally present. They also typically present with otoscopic finding of a retro tympanic vascular mass. A history of palpitations and headaches is suggestive of catecholamine excess but is extremely rare for head and neck paragangliomas. Catecholamine excess is found in the familial etiology group due to the concomitant presence of a pheochromocytoma in the paraganglioma syndromes. Since catecholamine excess is rarely found in head and neck paraganglia, in case it is discovered, it should be assumed to be from a synchronous thoracic or abdominal lesion unless proved otherwise.
Fig 1: Retrotympanic reddish mass
High-resolution computed tomography (HRCT) and T1-weighted (T1W), T2-weighted (T2W), and T1-weighted gadolinium-enhanced MRI sequences are necessary for identification of the suspected pathology as also the extent of the lesion. HRCT scan will show a moth-eaten appearance of the bone of the jugular fossa and erosion of the caroticojugular spine. Paraganglia give a low to intermediate signal on T1W and a high signal on T2W sequences. The salt and pepper appearance seen on T2W images is due to intratumoral vasculature appearing as flow voids. The scans give adequate information about the likely pathology and thus no biopsy is required for confirmation of the diagnosis.
In the case of any suspicion, a 24-hour urine sample is analyzed for epinephrine, dopamine, and vanillymandelic acid. If elevated, 1,231-metaiodobenzylguanidine (mIBG) scintigraphy and MRI of the chest and abdomen may be used to localize the additional extracranial lesion.
Fig 2: T1-weighted gadolinium-enhanced MRI sequences showing an extensive TJP.
Fig 3: HRCT scan showing moth-eaten appearance of the bone of the jugular fossa and erosion of the caroticojugular spine
Management Based on the scans, the lesion is staged. Staging for glomus was popularized by Fisch and modified by Sanna. The current therapeutic approaches towards tympanojugular paragangliomas include surgical resection, irradiation, steretotactic radiosurgery with a Leksell gamma knife, or combinations of all modalities.
The aim of the surgery is a radical removal of the tumour with a minimal morbidity. Various surgical approaches and treatment modalities has been discussed in the literature regarding large tumous. Radical treatment of these tumours is possible due to microsurgical and complex techniques, including preoperative embolization. Nowadays, the tumour control is achieved in 80–90% in most surgical series.
To study the vascular supply of the glomus tumor, angiography is performed prior to superselective embolization of the feeder vessels. The embolization is preferred around 48 h prior to surgery, commonly using polyvinyl alcohol as the embolic material. Devascularization of the glomus tumor reduces its size, makes it firmer in consistency and decreases blood loss during surgery. Embolization of feeders from the external carotid artery and its ascending pharyngeal branch is routinely performed.
For small C1 tumors with minimal jugular bulb involvement, the hypotympanic approach has been described. A transjugular approach with preservation of the facial nerve may be used for C1 glomus jugulare tumors with a predominantly posterior or an intracranial extension. Preservation of the posterior canal wall in class C tumors invites the risk of leaving behind residual tumor. Hence, in class C tumors, the recommendation is to perform a "canal wall down mastoidectomy" with drilling of the tympanic bone, excision of the styloid process, and obtaining a good exposure and control of the internal jugular vein, ICA, and lower cranial nerves in the jugular foramen and neck. All these steps are incorporated in the infratemporal fossa A approach described by Fisch.
Surgical technique of the infratemporal fossa A approach for exposure of the jugular foramen
A C-shaped incision is taken from the top of helix in the midtemporal area, 2.5-3 cm behind the postaural groove upto the mastoid tip, coursing two finger-breadths below the angle of mandible up to the greater cornu of the hyoid bone. The skin and subcutaneous layers are elevated and reflected anteriorly. The neck flap is elevated in the subplatysmal plane. A rectangular-shaped musculoperiosteal layer is created just posterior to the external auditory canal, which helps in a two layered cul-de-sac closure of the external auditory meatus. The external auditory canal is transected circumferentially at the level of the spine of Henle. The cartilage is excised from this lateral half of the transected external auditory canal till a circumferential skin cuff is created which is everted and sutured as the first layer of cul-de-sac closure of the external auditory canal. The rectangular musculoperiosteal layer created earlier is used as a second layer closure. The skin of the medial half of the external auditory canal together with the malleus and the incus (after dislocation of the incudostapedial joint) is excised. The greater auricular nerve that courses along the lateral surface of the upper part of the sternocleidomastoid muscle is preserved or harvested. The anterior border of the sternocleidomastoid muscle is separated from its covering cervical fascia, and its attachment to the mastoid is divided. This helps to retract the sternocleidomastoid muscle and the temporalis muscles posteriorly. The ICA, external carotid artery, and the internal jugular vein are identified, and silicone tubing is loosely placed around them for later control if needed. The IX, X, XI, and XII cranial nerves are identified. The facial nerve distal to the stylomastoid foramen is delineated including its distal upper and lower divisions in the parotid gland.
"canal wall down mastoidectomy" is performed. The mastoid tip is excised. The facial nerve is decompressed in 270 degrees circumference from the geniculate ganglion till the stylomastoid foramen area. At the stylomastoid foramen area, the periosteum is left around the facial nerve. The facial nerve is lifted off its bed and freed from the geniculate ganglion till the distal upper and lower divisions in the parotid . The facial nerve is then transposed anteriorly by lodging it in the parotid tissue and suturing the parotid tissue over the nerve so as to create a tunnel for the facial nerve. The tympanic bone is drilled off. The styloid process is exposed by dissecting the muscles off it and excised. This exposes the underlying ICA. The bone over the sigmoid sinus and jugular bulb is taken off to expose the tumor over the jugular bulb. However, a small shelf of bone is kept intact over the upper end of the sigmoid sinus to facilitate its extraluminal packing. The infracochlear cells are drilled off. The drilling can extend anteriorly to expose the infratubal vertical segment of the ICA when desired based on the tumor spread. In type C3 tumors, the infratemporal B approach is used. In this approach, the anterior canal wall is drilled off, and the temporomandibular joint is exposed. Drilling proceeds anteriorly from the base of zygoma. The middle meningeal artery and mandibular nerve are transected. The horizontal petrous segment of the ICA is exposed along with the tumor over it. Drilling can proceed anteriorly until the foramen lacerum where the ICA is seen to course superiorly along its paraclival segment. In case the tumor has destroyed the cochlea and is infiltrating toward the petrous apex, a transcochlear approach is performed. When the tumor extends into the sphenoid sinus or the nasopharynx, these need to be opened up. This forms the basis of infratemporal fossa C approach. In tumors extending posteriorly from the jugular foramen, a far or extreme lateral approach is performed depending on the tumor spread.
Fig4: Infratemporal Fossa Type A approach: tumour clearance with IJV ligation and Sigmoid sinus extraluminal packing and anterior rerouting of facial nerve.
Management of the facial nerve
Management of the facial nerve that appears involved has been clearly defined by Fisch. In cases of grade I involvement (tumor is 1mm or more from the perineurium), the tumor bulk is gently dissected away from the facial nerve epineurium. In grade II involvement (epineurium invaded), the epineurium is resected leaving the perineurium intact. When the perineurium (grade III) or endoneurium (grade IV) is invaded, the nerve needs to be resected and an end-to-end anastomosis or an interposition nerve grafting is performed between the two cut ends of the facial nerve. Grafting is performed using greater auricular or sural nerve grafts. Rarely, in cases where grafting is not feasible due to extensive involvement of the proximal segment of the facial nerve, a second stage facial-hypoglossal anastomosis is an option.
Management of ICA
In cases with proven involvement of the wall of the ICA, a preoperative balloon occlusion test is mandatory. The surgical options include sacrifice of the involved ICA (with bypass, when the cerebral cross-circulation is inadequate) or its preoperative stenting. Preoperative stenting is nowadays preferred to the carotid artery sacrifice. Preoperative stenting of the ICA also facilitates removal of the tumor closer to its lumen without the risk of its rupture.
Management of the sigmoid sinus and the jugular bulb
A thin shelf of bone is left over the upper end of the sigmoid sinus. This is to facilitate its extraluminal compression to control venous bleeding during surgery. An extraluminal compression is the preferred option to control venous bleeding than intraluminal compression as the latter is associated with the possible risk of embolization as well as the risk of retrograde thrombosis of the transverse sinus and the vein of Labbe.
The internal jugular vein is ligated in the neck. It is dissected off the surrounding tissues and passed under the accessory nerve toward the jugular foramen. The lateral wall of the sigmoid sinus is excised along with the tumor and the internal jugular vein. At this point, brisk bleeding ensues from the openings of the inferior petrosal sinus located in the medial wall of the jugular bulb. These openings are meticulously packed with surgicel without any undue pressure since the lower cranial nerves traverse beneath the medial wall of the jugular bulb. Bleeding also arises from the posterior condylar vein, which is also controlled with surgicel. Complete ligation and excision of the sigmoid sinus is avoided as requires an additional dural patch to prevent a cerebrospinal fluid leak.
Small intradural extensions may be excised along with the involved dura in a single stage. However, in larger defects, it is not always possible to plug the defect securely. The opening of the fascial planes in the neck and extensive bony drilling further prevents a watertight dural closure. It is easier to seal dural defects in the second stage due to a smaller area of exposure and prior closure of communication with the fascial spaces in the neck.
Tumor involving the vertebral artery
Posteriorly based paragangliomas may involve the vertebral artery, lower clivus, and foramen magnum and require a far lateral or extreme lateral transcondylar approach for adequate exposure.
Role of Gamma Knife Radiosurgery
Stereotactic radiosurgery, by inducing vascular endothelial damage, may be particularly effective for vascular tumours, such as a glomus. Surgery is associated with higher morbidity rates but has the advantage of immediately and eliminating the tumor. The results of radiosurgery are promising; however, the incidence of long-term recurrence is at present not well defined. There is a consensus that surgery is the preferred option in young patients, in those with a catecholamine secreting paraganglioma, and in those with rapidly progressive neurological deficits. As the target volume of the tumor increases, there is a proportional increase in the radiation dose on the surrounding normal tissues. For this reason, stereotactic radiosurgery is not suited for large lesions. However, for residual or small recurrent lesions, stereotactic radiosurgery is very effective.
Management of glomus jugulare tumors requires a good knowledge of the temporal bone and cervical as well as intracranial anatomy to evaluate the extent and progression of the tumor and the type of surgical approach required. Surgery is the preferred option in the young and in medically fit middle aged to elderly patients in whom total extirpation of the tumor is the aim. Extensive infiltration of lower cranial nerves or the dominant vessels is an indication for a more conservative excision of the lesion. Improved surgical techniques have considerably decreased surgical morbidity. Speech and swallowing therapy as well as extensive physiotherapy have helped to overcome the morbidity arising due to lower cranial nerve paresis or palsy. In the elderly and medically unfit subjects with minimal symptoms, a close observation is an option. These subjects, if significantly symptomatic or showing disease progression, may be subjected to stereotactic radiosurgery. Stereotactic radiosurgery is the preferred option in residual or small recurrent tumors.