Various sites: carotid body, glomus vagale, and glomus tympanicum tumors.
Hereditary pattern: It shows autosomal dominant inheritance with variable penetrance.
Endocrine activity: Even though these tumors are considered non chromaffin paragangliomas with no endocrine activity, some cases with endocrine activity by these tumors have been reported. It is hence important to look for evidence of endocrine activity by urine estimation of VMA (Vanillyl mandelic acid).
Glomus tumors sometimes may show multicentric presentation i.e. present in both ear, or in conjunction with other paragangliomas. The carotid body being commonly the second site.
Pathophysiology:
Glomus tumors are encapsulated, highly vascular, and locally invasive tumors. Inside the temporal bone they tend to expand along the pathway of least resistance such as air cells,vascular lumen, skull base foramina and eustachean tube. They also invade and erode bone in a lobular fashion. The middle ear ossicles are commonly spared. Initially skull base erosion occur in the region of jugular fossa and postero-inferior part of petrous bone. Later on extension occurs to the mastoid and adjacent occipital bone.
The parenchyma of paraganglia consist of two primary cell types. Type I cell are more common and are typically round with distinct cell boders. Type II cells are smaller and irregularly shaped.
Presentation:
Presenting Features of Glomus jugulare:
Synonyms: Paraganglioma, Chemodectoma, Gangalia tympanica, vascular tumors of middle ear.
Definition: Glomus jugulare is defined as a collection of ganglionic tissue within the temporal bone in close relationship with the jugular bulb. The jugular bulb is closely related to the floor of the middle ear cavity (i.e Hypotympanum).
History: Valentine in 1840 describe this condition as ganglia tympanica. Guild recognized its historical relationship with the carotid body. Lattes and Waltner suggested that the ideal generic term for these structures is non-chromaffin paraganglioma.
Paraganglia cells are derived from the neural crest and are found widely distributed in the autonomic nervous system. Paraganglia having negative chromaffin reaction are termed non average three glomus bodies were found in them . Thy were usually found in close relationship with the tympanic branch of glossopharyngeal nerve and the auricular branch of vagus. They are supplied from branches from the ascending pharyngeal artery.
Even though the paraganglia cells are closely related to either the tympanic branch of glossopharyngeal nerve or the auricle branch of vagus , there position in temporal bone is highly variable. Commonly they are found in the adventitial layer of the jugular bulb. In about 25% of cases they may be found over the mucosa of the promontory. Historically, they resemble carotid body.It contains epitheloid cells interspersed in highly vascular stroma of capillary and precapillary vessels.The proportion of the cellular and stromal components vary.
Guild classified glomus tumors into two types depending on the amount of cellular and stromal components:
Their sizes could be variable, but mostly they are ovoid in shape.
Paragangliomas of temporal bone are generally divided into
The predominance of the paraganglia within the jugular fossa likely accounts for the increase frequency of tumors with this origin.
Classification system that have been develop for temporal bone paragangliomas are used for staging purposes, surgical planning, and comparison among different therapeutic modalities.
Incidence: Glomus jugulare occurs in about 1 in 100000 patients. It is 6 times more common in females when compared to men.
Clinical features: Otoscopic examination reveals a characteristics, pulsatile, reddish-blue tumor behind the tympanic membrane that often is the beginning of more extensive findings (i.e the trip of the iceberg). When the drum is examined under the microscope will show a pulsation of the reddish mass behind the drum. On seigalisation the mass blanches. This sign is known as brown sign. This is pathognomonic of glomus tumor. Audiologic examinatin reveals mixed conductive and sensorineural hearing loss. The sensorineural components tends to be more significant with larger tumors.
CLASSIFICATION
Glasscock- Jackson classification of temporal bone paraganglioma:
Type I: Small tumor involving the jugular bulb, middle ear and mastoid.
Type II: Tumor extending under the internal auditory canal. There may be intracranial extension.
Type III: Tumor extending into the petrous apex. There may be intracranial extension.
Type IV: Tumor extending beyond the petrous apex into the clivus and infratemporal fossa. There may be intracranial extension.
Fisch classification: The Fisch classification of glomus tumors is based on extension of the tumor to surrounding anatomic structures and a closely related to mortality and morbidity.
Type A tumour – Tumor limited to middle ear (carries the best prognosis)
Type B tumour – Tumor limited to the tympanomastoid area with no infra-labyrinthine compartment involvement
Type C tumor – Tumor involving the infra-labyrinthine compartment of temporal none with extension to petrous apex. This is divided into three types : C1, C2 and C3.
Type D tumor has 2 types
INVESTIGATIONS
Radiological investigation help in diagnosis.
Plain X ray skull: May show enlargement of lateral jugular foramen and jugular fossa.
CT scan and Contrast MRI using Gadolinum enhancement is very helpful in delineating tumor extension.
Applied anatomy of jugular bulb area:
The posterolateral portion of the foramen (pars venosa) contains the jugular bulbs, posterior meningeal artery, and cranial nerves X and XI. The anteromedial portion (pars nervosa ) contains the inferior petrosal sinus and cranial nerve IX. The jugular bulb is situated between the sigmoid sinus and the internal jugular vein. The lower cranial nerve are situated medial to the medial wall of the jugular bulb. The inferior petrosal sinus enters the medial aspect of the jugular bulb via several channels anterior to cranial nerves IX, X and XI.
Many important structures are in proximity to the jugular bulb, including the internal auditory canal, the posterior semicircle canal, the middle ear, the media external auditory canal, the facial nerves(posterolaterally) , and the ICA (anteriorly) within the carotid canal. At the extra cranial end of the jugular foramen, the ICA, internal jugular vein, and cranial nerves VII, X, XI and XII are within a 2-cm area.
Differential diagnoses include the following:
TREATMENT:
Treatment is mainly surgical. Complete resection of the mass is curative. Since it is a vascular tumor pre-operative intravascular embolization may help to reduce bleeding during surgery.
The particular surgical approach used to resect temporal bone paragangliomas depend on the location and extend of tumor. Paragangliomas originating from the promontory of the middle ear and isolated to the mesotympanum can be resected by elevating the tympanic membrane and removing the tumor using micro dissection techniques. If te tumor extends into the hypotympanum or the mastoid, a tympanomastoidectomy is performed and the tumor respected.
In extensive Fisch type 3 tumors the mass can be approach with help from neurosurgeons. The skull base approch ensures better exposure of the mass and facilitates complete resection.
Management of Fisch type 4 tumors is highly controversial. Irradiation of the mass has been tired with very little effect. Considering the slow growth rate of these tumors with a very long doubling time, these patients are best left alone with symptomatic treatment of the complications.
Complication of surgery:
Complication of surgery include death, cranial nerve palsies, bleeding, cerebrospinal fluid (CSF) leak, meningitis, uncontrollable hypotension/hypertension, and tumor regrowth.
Protection