Timothy C. Hain, MD. •Page last modified: December 4, 2022
|Structures of the ear. Most tinnitus is due to damage to the cochlea (#9 above)|
It is common for persons with pulsatile tinnitus to have some sort of procedure done in the Radiology department, looking for something that can be fixed. Usually these show nothing. Rarely they find something important. Even when "something is found", usually there is nothing to do other than say -- maybe this is causing your tinnitus.
According to Branstetter and Weissman (who are radiologists, and of course emphasize Xray or MRI evaluation), entities that can cause unilateral pulsatile tinnitus include:
- Aberrant internal artery (congenital)
- Dehiscent internal carotid artery
- Aberrant anterior inferior cerebellar artery (that loops into the ICA)
- High riding jugular bulb.
- Dehiscent jugular bulb (best seen on coronal images)
- Aberrant sigmoid sinus (displaced anteromedially from its normal course)
- Stenosed dural sinus (Best seen on MRV or CT-venography)
- Persistent stapedial artery (isolated aberrant vessel in the inner ear, seen on CT). The ipsilateral foramen spinosum is absent in these patients.
Other entities than the ones listed above that can sometimes be seen on radiological testing and that can cause pulsatile tinnitus, include AVM's, aneurysms, carotid artery dissection, fibromuscular dysplasia, venous hums from the jugular vein (found in half the normal population), vascular tumors such as glomus, ossifying hemangiomas of the facial nerve, osseous dysplasias such as otosclerosis and Paget's, and elevated intracranial pressure.
Practically, MRI/MRA or CT is often suggested in younger patients with unilateral pulsatile tinnitus. In older patients, pulsatile tinnitus is often due to atherosclerotic disease and it is less important to get an MRI/MRA. A lumbar puncture may be considered if there is a possibility of benign intracranial hypertension. More invasive testing includes the "balloon occlusion test", where a balloon is blown up in the internal jugular vein to see if it eliminates tinnitus. These are very rarely done.
If tinnitus goes away with compression of the Jugular vein in the neck, it is usually not going to help to get any kind of radiology procedure. On the other hand, if somebody else can hear tinnitus (with a stethoscope on the skull), that is a good reason to get a vascular procedure. In 2021, MRI/MRA is generally the best choice, as it has high resolution and has no radiation. The purpose of the MRI is to look for intracranial hypertension. In our opinion, a "Time resolved MRA", is usually the second step after an MRA is done and is abnormal. Selective catheter angiograms are unreasonably dangerous. CT angiograms, done with venous contrast, combine high radiation with low yield.
Ubbink et al (2022) reported on using a high-tech method of diagnosing objective tinnitus, involving placing a small microphone in the ear canal. This method is not yet generally available, but appears promising.
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 the French word for noise) from a narrowed IC may cause tinnitus.
Some authors claim that branches of the anterior inferior cerebellar artery, AICA, may abut the 8th nerve and cause tinnitus. AICA is the source of the labyrinthine arteries(s), which supply blood to the inner ear. We find this idea dubious as the 8th nerve has no hearing receptors. Practically, the inner ear needs blood and sometimes the branches of the labyrinthine artery are tortuous, but is there is no practical investigation to confirm that microvascular compression is causing tinnitus. It is possible.
This lengthy discussion was moved the a separate page (davf)
This subject is discussed on a separate page.
Pulsatile tinnitus can also be associated with benign intracranial hypertension (BIH), also known as pseudotumor cerebri. Pseudotumor cerebri is discussed here.
Sigmoid sinus diverticulum/dehiscence is another cause of venous tinnitus. Sun and Sun (2019) discuss reconstruction of the sigmoid sinus wall. As of 2020, we have never encountered this procedure in our clinical context in Chicago Illinois.
The "whooshers" website has a large amount of information on pulsatile tinnitus.