May 16, 2023
Glomus tumor is a tumor originating from the para-ganglionic cells. Para ganglionic cells are the cells of the sympathetic nervous system and are responsible for auto-regulation. The para-ganglionic cells are also known as glomus bodies. One very important feature of the para ganglionic cells or the glomus bodies is that they secrete catecholamines, namely epinephrine, nor-epinephrine, and dopamine. Glomus is a benign tumor but is a locally invasive tumor.
These glomus bodies or the para ganglionic cells are seen in the major blood vessels, near the aortic arch, near the common carotid, internal and external carotid, and the internal jugular vein, because these blood vessels carry major blood supply to our body and chemoreceptor are needed in such areas to sense if there is an elevation, decrease in the pressure, decreased oxygenation, increased carbon dioxide, and to maintain internal homeostasis.
The chemoreceptor in this case will be the glomus bodies. These glomus bodies are found around major blood vessels. If something inappropriate is happening these will immediately compensate for it. The Glomus tumor is the most benign tumor of the middle ear. The glomus bodies are the para -ganglionic cells of the sympathetic nervous system. They are present around major blood vessels like the aortic arch, and jugular vein, and are responsible for auto regulation. Glomus tumors originating from the para ganglionic cells are called paragangliomas. Glomus is one such paraganglioma which secrete catecholamines. Because the glomus tumors secrete catecholamines there will be a sympathetic excess. The two types of glomus tumors are:
i. Glomus Tympanicum
ii. Glomus Jugulare
Read this blog further to get a quick overview of this important topic for ENT preparation and ace your NEET PG exam preparation.
Benign and slow growing Thin walled blood sinusoids with no contractile muscle – hence excessive bleeding; extremely vascular No capsule and hence locally invasive Microscopically, glomus tumors have loose blood sinusoids. The blood vessels in this tumor typically lack the tunica media layer or the smooth muscle layer. This will cause the blood vessels to not be able to contract. Therefore, from these areas, one can present with profuse bleeding. When there is a glomus tumor in the scenario, one must think of profuse bleeding as a clinical manifestation. So, there is a lack of tunica media. These tumors have no capsules causing the tumor to be able to spread locally to the adjacent sides. The arrangement of cells present in the tumor, microscopically when seen, resembles a pattern. This pattern is called the Zell Ballen pattern.
This means that it is not a rule that every glomus tumor will secrete catecholamines. Only 10% of such tumors secrete catecholamines. Multicentric means that it can happen on multiple sites. Glomus tumors can be associated with Von Recklinggausen neurofibromatosis, Sturge Weber syndrome, tuberous sclerosis, and Von Hippel Lindau disease. (clinical MCQs)
Spread of glomus tumor
Glomus is a locally invasive lesion due to the lack of capsules. The roof of the middle ear is formed by the tegmen tympanum which separates the middle ear from the middle cranial fossa. If the tumor goes superiorly it can enter the middle cranial fossa.
Bleeding - Because it is an extremely vascular tumor and the blood vessels like the smooth muscle layer, when it starts to bleed, it will bleed profusely.
Gradually Progressive Conductive Hearing Loss - Loss of conduction of sound from the external ear into the middle ear happens gradually over time along with the growth of the tumor.
Pulsatile Tinnitus - Typically the tumor comes from the sympathetic plexus that surrounds the blood vessels. When blood flows from these major blood vessels, transmitted pulsations go to the tumor which can be heard by the patient. The patient will complain of hearing sounds in the year that resembles the heartbeat, in such a case. There is pulsatile tinnitus. When one is complaining of pulsatile tinnitus, the glomus tumor must be ruled out. Pulsatile tinnitus is always suggestive of a glomus tumor.
Rising Sun Appearance - If there is a mass in the middle ear, it can either be a glomus tympanicum or it can be a glomus jugulare. But when one sees from the external auditory canal, red bulging can be seen in the tympanic membrane in the case of glomus tympanicum. In patience with glomus jugulare, a red reflex is present on the floor of the middle ear that represents a Rising Sun. This appearance is a very important sign in patients with glomus tumors. The slide to the left shows a red reflex on the floor of the middle ear suggestive of glomus jugulare. When there is a tumor originating from the promontory, it looks like the slide on the right where the tympanic membrane is red and bulging.
The Brown Sign - There is a glomus jugulare tumor in the middle ear. If a Seigel's Pneumatic Speculum is put in the external auditory canal, and the cuff is inflated, the pressure in the middle ear will increase. This will cause the tumor to vibrate vigorously and become pale, turning to a pink-brown. However, it will again become red. This pink-brown color is known as the brown sign.
Acquinos Sign - These tumors typically get their blood supply from branches of the ICA (ascending pharyngeal artery). Near the hyoid bone, the common carotid bifurcates into internal and external. If the ICA is compressed by applying pressure on the neck and then waiting for some time, the blood supply to the ascending pharyngeal artery is reduced, and therefore the blood supply to the tumor will get cut off. The red tumor will start becoming pale as can be seen through an otoscopic examination.
Clinical features based on the spread
Glomus tumor is a paraganglioma and secretes catecholamines (adrenaline, noradrenaline, and dopamine) in 10% of the patients (rule of 10) causing sympathetic excess. Such a patient can present with:
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Embolization followed by Surgical excision
In the CECT, a very typical sign is seen which is the Phelps sign. It is a radiological sign. As can be seen in the slide there is the ICA bulge on both sides.
The sigmoid sinus then identifies which lies in the posterior border of the mastoid; it continues towards the internal jugular vein. A dense bone is present between the jugular and the mastoid called the carotico-jugular spine.
On the disease's side, this bone is absent. Some soft tissue is present there, which is the glomus tumor that eroded the bone. The erosion of the carotico-jugular spine bone is called the Phelps sign.
MRI showing Salt and Pepper appearance
The MRI of a patient suffering from a glomus tumor will have areas that are white and areas that are grey (due to the microhemorrhages that happen within the tumor). White and grey dots can be seen in the slide above. This appearance is called the Salt and Pepper appearance.
A-Tumors restricted to middle ear (glomus tympanicum tumor)
B-Tumors restricted to tympanomastoid site
C-Tumors involving the infra-labyrinth portion towards the petrous apex
D1-Tumor with intracranial invasion (<2cm)
D2-Tumor with intracranial invasion (>2cm)
This is everything that you need to know about Glomus tumor for your ENT preparation. For more interesting and informative blog posts like this download the PrepLadder App and keep reading our blog!
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