Timothy C. Hain, MD. Tinnitus Page Page last modified: November 26, 2011
|Structures of the ear. Most tinnitus is due to damage to the cochlea (#9 above)|
This is a congenital anomaly in which the internal carotid can present as a middle ear mass. If the carotid fails to develop correctly during fetal life, the inferior tympanic artery enlarges to take it's place. It enters the skull through it's own foramen, courses through the medial part of the middle ear, and then rejoins the petrous ICA (Branstetter and Weissman, 2006).
Dehiscent internal carotid.
The ICA may not have a bony covering as it courses through the middle ear.
Stenosed internal carotid
A bruit from a narrowed IC may cause tinnitus.
Some authors claim that branches of the AICA may abut the 8th nerve and cause tinnitus. We find this idea dubious.
Arteriovenous fistulae cause loud noises, synchronous with the pulse, that can often be heard by others with a stethescope, or sometimes by simply putting one's ear next to the person's head. These sorts of fistulae can often be embolized. Extra caution is needed when the fistula is in the posterior circulation (i.e. fed by the vertebral artery), as it is difficult to thread a catheter through these tiny arteries. It is easy to cause a "vertebral dissection", possibly accompanied by a stroke.
It may seem silly to say this, but in our opinion, it is generally not worth taking on a significant risk of having a stroke to attempt to get rid of a noise in one's head with embolization. The US health care system pays interventional radiologists very well to do embolization, and of course, they have some motivation to improve people's lives through their training. Nevertheless, the decision whether to go forward with a dangerous procedure should ideally be made by the patient's treating physician, rather than a radiologists. Decisions should not reasonably be made by the radiologist who is trained to thread a catheter into a patient's head, but has no long term relationship with the patient, and also generally has had no clinical training in otolaryngology or neurology. We suggest getting a 2nd opinion from a non-radiologist expert before proceeding with embolization for tinnitus. To avoid conflicts of interest, the expert should not do this procedure themselves and preferably they should work for another medical insitution.
|AV fistula associated with pulsitile tinnitus. Courtesy of Dr. Marcello Cherchi.||Dural AV fistula of the transverse sinus associated with pulsatile tinnitus. Courtesy of Dr. Dario Yacovino.|
This is a venous tinnitus, associated with an unusually located jugular vein. A high-riding jugular bulb is a common vascular anomaly, found in 2.4-7% of temporal bones. The jugular bulb is not present at birth, but develops over time. The size and location is somewhat dependent on pneumatization of the mastoid bone. (Friedman et al, 2009).
Another variant of the high jugular bulb is a jugular bulb diverticulum - -an outpouching of the jugular bulb - -into the inner or middle ear. Most commonly the outpouching is into the middle ear. This occurs in 6% of the otherwise normal population. According to Kupfer et al (2011), dehiscence in pediatric patients occurs in 8.6% of pediatric patients undergoing temporal bone CTs (one wonders why they were having temporal bone CT's). In this population, it was concluded that they were "unable to unable to identify any relationship between JBVAD and hearing loss". Of course, this leaves entirely open the question of whether jugular bulb dehiscence contributes to hearing loss in older persons as well as dizziness and tinnitus.
When present, this structure can be associated with bleeding during surgery. When it comes into contact with inner ear structures, it can cause tinnitus, hearing loss, a conductive hyperacusis, and Meniere's disease type symptoms. Tinnitus is attributed to a direct pressure wave from the Jugular. Conductive hyperacusis to increased compliance of the inner ear, in similar way as is seen in superior canal dehiscence and Fenestration surgery patients. Meniere's disease symptoms, due to increased compliance. Considering the high frequency of jugular bulb anomalies (about 5%), and low prevalence of Meniere's disease (about 1/2000 people, or 0.2%), it would seem possible that Meniere's disease might be caused by jugular bulb dehiscence.
The jugular bulb diverticulum is a much rarer anomaly than high riding jugular bulb (Stern and Goldeberg, 1980) . It can be associated with sensorineural hearing loss, tinnitus and vertigo. (Shihada et al, 2008), and may account for some cases of Meniere's disease (Yazawa et al, 1998).
Diagnosis is mainly via MRI/MRA with contrast or similar techniques that show blood flow in relation to the skull. However, MRI is not especially sensitive (Friedman et al, 2009). High-resolution CT-angiography is the method of choice, but because it is associated with some radiation, it is generally not the best choice as a screening procedure. On CT, a jugular bulb diverticulum is characterized by continuity with the jugular bulb, smooth edges, and absence of bony destruction. Some have reported that it can be diagnosed by other maneuvers, such as ultrasonography (e.g. Nakagawa et al, 2008), but we have not seen this done at any institutions that we are aware of in Chicago. VEMPs can be of low threshold on the side of the dehiscence.
No treatment is available for jugular bulb dehiscence.
Abberant sigmoid sinus and stenosed dural sinuses can also cause venous tinnitus.
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