Glomus tumors are the most common benign tumors of the middle ear. They arise from glomus bodies. Glomus bodies are tiny, normal structures in the middle ear which serve as baro receptors. These baro receptors sense and help to regulate the oxygen pressure in the middle ear and mastoid.
Benign tumors of glomus bodies can occur within the middle ear or at other sites: the temporal bone and neck, or within the jugular vein (the large vein in the upper neck which drains the head toward the heart). Glomus tumors of the middle ear are more common than glomus tumors of the jugular vein. They can result from abnormal growth of a single glomus body.
Glomus tumors are highly vascular (blood sensitive) and are primarily composed of blood channels flowing through the tumor itself. They appear red on examination of the eardrum. Most glomus tumors are readily noted by a primary care physician’s routine examination of the ear. They appear as a red ball or mass behind the eardrum. The eardrum may pulsate, if the glomus tumor is touching the under surface of the intact eardrum.
This symptom is called pulsatile tinnitus. Most patients with glomus tumors of the middle ear can hear a pulsing sound in the ear on the side which has the tumor. Pulsatile tinnitus occurs as the tumor enlarges and presses against the bones of hearing. It is the actual pulsation of blood which distorts the movement of the bones of hearing.
Glomus tumors can grow very large. As the glomus tumor of the middle ear expands, it can grow into the mastoid itself or through the wall that divides the middle ear from the mastoid and deeply infiltrate the bone. The tumor may also wrap around and infiltrate areas around the facial nerve, as it enlarges. It can become attached to the jugular vein and carotid artery. In these cases, the tumor is more difficult to remove and radical surgery is necessary.
If the glomus tumor fills the middle ear space, hearing loss becomes a prominent symptom. However, in small glomus tumors of the middle ear, hearing can be quite normal and there may be no symptoms at all. The tumor itself is often identified on routine exam as being a red spot behind the eardrum. The size and extent of the glomus tumor of the middle ear can be well assessed by microscopic examination. Additional examinations are necessary to define the tumor.
Imaging Studies of Glomus Tumors
Imaging studies, including a CT scanning, MRI scanning and MR angiography, should be obtained to determine the limits and extent of any glomus tumors. It is necessary to differentiate between a glomus tumor limited to the middle ear, and a glomus tumor arising from the jugular vein. At the time of initial examination of the ear, the two may be indistinguishable. They are classified by area and degree of involvement. The classifications are:
I. Glomus Tympanicum (Middle Ear Glomus Tumors)
a. Glomus Tumor: middle ear
b. Glomus Tumor: middle ear and mastoid
c. Glomus Tumor: middle ear, mastoid and brain
II. Glomus Jugulare
a. Glomus Jugulare: limited to the jugular blub area
b. Glomus Jugulare: jugular blub, mastoid, middle ear
c. Glomus Tumor: jugular bulb, middle ear, mastoid and brain
Ia. If the glomus tumor appears to be filling the lower half of the middle ear, it can be either a glomus tumor of the middle ear (limited to the middle ear), or a glomus jugulare which has eroded the bony covering of the jugular vein as it comes in touch with the lower portion of the middle ear space. For this reason, imaging studies are essential to evaluate larger tumors.
A CT demonstrates whether the bone in the lower portion of the middle ear connects to the jugular bulb. If there is a distinct bony covering of the jugular bulb and separation of the tumor from the carotid artery, the ear surgeon can inform the patient that the surgery will be limited primarily to the middle ear and not involve the blood vessels of the neck. If, however, there is erosion of the floor of the middle ear and jugular blub, CT scaning will provide the information.
An MRI (Magentic Resonance Imaging) is also useful. However, a more useful test for glomus tumors is today’s MRA (Magentic Resonance Angiography). At one time, most angiograms were performed by injecting a dye into an artery, often inserting a catheter through the femoral artery in the thigh and running the catheter up to the area of concern. Today, the MRA is a non-invasive way to obtain the same information. The MR Angiogram is extremely useful in defining the source, size and feeding vessels entering the glomus tumor.
Ib. Glomus tumors of the middle ear and mastoid are generally treated by surgery alone. However, the larger, so-called glomus jugulare tumors, arising from the jugular vein, may be extremely vascular and are situated deep in the bone of the ear and neck.
Embolization of Glomus Jugulare Tumors: Blocking Blood Supply
Before routine embolization, blocking the blood supply of glomus tumors, was used. Large amounts of blood were lost during surgery. In recent years, with the perfection of new techniques used by the radiologist, feeding vessels to the tumor can be selectively found and blocked during angiography. Tiny balls of microscopic biocompatiable sponge are injected into the tumor. This procedure is usually performed 24 hours before surgery, greatly reducing the blood supply to the tumor.
With embolization of large glomus jugulare tumors, transfusion is not usually necessary. Thus the procedure can be performed with greater safety. Also the preservation of vital structures around the tumor is enhanced, including cranial nerves going to the throat, vocal cords and face.
Preoperative Assessment of Glomus Tumors
Once the ear surgeon has determined the classification of glomus tumor, a careful evaluation of the x-ray results must be made in order to make certain there are no tumors associated with other blood vessels.
Glomus tumors are similar to chemodectomas, blood vessel tumors occurring in bodies similar to the glomus body. These tumors can occur along the carotid artery, the major arterial blood supply to the brain. They can also occur along other important portions of the blood supply in the neck and throat. It is important to be certain that there are no other associated glomus tumors or chemodectomas at the time of primary glomus tumor diagnosis.
Glomus tumors do not metastasize. They do not spread by blood borne pieces breaking off and traveling to distant sites. However, their local invasiveness means that glomus tumors can be highly destructive and difficult to remove.
Surgery of the Glomus Tympanicum (Glomus Tumor of the Middle Ear)
The size and the extent of the glomus tumor determine the procedure needed. Examination of the eardrum helps the ear surgeon to estimate the size of the tumor. In very early cases, glomus tumors can be as small as 2 to 3 mm. and appear as a red ball behind an intact tympanic membrane (eardrum).
As glomus tumors expand, they begin to fill the middle ear. Some glomus tumors of the middle ear start by growing from the floor of the ear upward. These are the tumors difficult to distinguish from glomus jugulare tumors. A CT scan or other radiologic findings are needed in these cases.
Many glomus tympanicum tumors can now be approached through the ear canal by elevating the eardrum and then destroying the tumor completely with an Argon or CO2 laser versus more radical surgeries performed in the past.
The laser is an extremely useful tool for removing glomus tumors. A larger Argon .4 to .6 mm. fiber is used instead of ordinary fibers used in ear surgery — .2 mm. in diameter. This larger fiber allows for ³blanching² (complete coagulation) of the tumor. As the laser energy is applied to the glomus tumor which is red, this energy is quickly absorbed into the outer pigment of the blood circulating through the tumor. The tumor turns white and succeeding layers of the tumor are vaporized. Along with the laser, we use a suction device which removes the char and smoke. Alternatively, CO2 laser can be utilized to vaporize the tumor (see video below).
Relatively large tumors of the middle ear can be approached by using the Argon or CO2 laser without opening the ear from behind. In using the Argon or CO2 laser, the bones of hearing can be preserved.
Larger tumors may surround the bones of hearing. In these cases, the tumor can be vaporized away from the bones of hearing without separating them in many cases.
Ib. Glomus Tympanicum Extending into Mastoid
When a glomus tumor extends into the mastoid, it becomes necessary to make an incision behind the ear and open the mastoid bone. Every attempt is made to preserve the wall that separates the middle ear from the mastoid. This approach is called an intact canal wall or facial recess approach. The mastoid is completely cleared of disease, judiciously using the laser. The facial nerve is monitored to prevent injury. The entire tumor can be removed in this manner.
Sometimes, the tumor may be attached to the jugular vein as it enters the mastoid bone. In these cases, the tumor must be completely removed from the jugular vein.
Invasion of the Jugular Vein
If the tumor appears to have invaded the jugular vein, then control of the blood vessels of the neck may be necessary with a separate incision in the neck before the tumor can be completely removed. This is the exception in glomus tumors which arise from the middle ear and mastoid, but the usual situation in glomus jugular tumors.
Ic. Invasion of the Brain
If the glomus tumor continues to expand, it may invade the brain through the bone separating the middle ear and mastoid. This bone is called the middle fossa plate, or tegmen.
If the tumor has invaded the bone and entered the brain, intracranial surgical excision of the tumor may be necessary. Depending on the size of the tumor, this part of the surgery is done in conjunction with a neurosurgeon at the operation. It can also be staged and performed at a separate operation. Staging is often chosen when very extensive tumors invade the brain.
Results of removal of glomus tumors of the middle ear and mastoid are extremely good in most cases, less so when the tumor has invaded the inner ear, facial nerve or brain. In long-standing tumors, or in very aggressive glomus tumors, the facial nerve may be invaded by the tumor itself. This condition can make it extremely difficult to separate the tumor from the facial nerve without damaging the facial nerve. In these cases, the canal wall separating the middle ear from the mastoid is generally removed when deeply invaded by tumor. A segment of the facial nerve may be removed and grafted.
II. Surgery of Glomus Jugulare Tumors
A team effort is usually preferred for glomus jugulare tumor surgery. The ear surgeon, the head and neck surgeon, and a neuroradiologist are all needed to remove glomus jugulare tumors.
Prior to surgery, the neuroradiologic evaluation is performed a day or two before surgery. The neuroradiologist (a radiologist who specializes in brain and head x-ray, studies and treatments) also performs an embolization (injection of microscopic sponge material to contain??? blood supply) of the tumor. The head and neck surgeon, ear surgeon and neurosurgeon, if necessary, perform a combined procedure which isolates the blood vessels in the neck. These feed the tumor. Thus, the removal of the tumor from the middle ear, mastoid and neck can now be done in a single unit. This is called an “enbloc” excision of glomus jugulare tumors. It is the best way to guarantee complete cure.
Although glomus tumors are benign tumors, they grow in extremely delicate areas: near nerves which control swallowing, the vocal cords, and the nerve that controls the facial muscles. Other nerves which also control the shoulder muscle are found in this region.
On our team, the ear surgeon performs the initial portions of the surgery isolating the facial nerve within the mastoid. The nerve is decompressed and taken out of its canal so that it can be preserved during the removal of the tumor. The bone around the capsule of the nerve is thinned using high speed air drills with constant water irrigation. Once the nerve is freed, the head and neck surgeon must identify the vessels in the neck leading to the tumor. The cranial nerves are also identified and tagged. The tumor is then removed. The ear surgeon and head and neck surgeon assist each other. In most cases, it is necessary to tie off or pack the jugular vein in the neck and the mastoid portion of the ear to prevent excessive bleeding at tumor removal.
Successful removal of the tumor may also require delicate dissection of the tumor from the carotid artery. This portion of the procedure is extremely delicate and requires the close cooperation of the head and neck surgeon, ear surgeon and, in some cases, vascular and neurosurgeons.
Using this team approach, the removal of glomus tumors has become a more successful procedure in terms of sparing vital cranial nerves. In addition, blood loss has been brought to a minimum and most patients do not require transfusion.
Glomus tumors are not highly radiosensitive (sensitive to the radiation therapy’s x-rays). However, in older patients, or those who should not undergo surgery, radiation therapy may help to arrest the growth of a glomus tumor. In the younger patient, complete surgical removal of the tumor after embolization is the preferred method of treatment.