Pulsatile tinnitus is due to a change in blood flow in the vessels near the ear or to a change in awareness of that blood flow. The involved vessels include the large arteries and veins in the neck and base of the skull and smaller ones in the ear itself. The blood flow can be altered by a variety of factors:
Generalised increased blood flow.
Blood that is flowing quickly generates more noise than blood that is flowing slowly. Increased blood flow throughout the body can occur in strenuous exercise orpregnancy. It can also occur in severe anaemia or when the thyroid gland is over active, a condition known as hyperthyroidism or thyrotoxicosis.
Localised increased flow.
Sometimes blood flow is increased in a single blood vessel or group of blood vessels rather than a generalised increase. For example, during foetal development we all
have an artery in our middle ear called the stapedial artery. This normally closes before birth but it can occasionally persist and in this case blood flow adjacent to middle ear structures can generate pulsatile tinnitus.
Turbulent blood flow.
If the inside of a blood vessel becomes irregular due to atherosclerosis (hardening of the arteries) the blood flow will become turbulent rather than smooth. This flow then becomes noisy in the same way that a smoothly running river will become noisier at a set of rapids or waterfall.
Altered awareness.
Awareness can be increased by several factors:
• Conductive hearing loss such as perforated ear drums or glue ear tend to make patients more aware of sounds inside their body because they no longer have the masking effect of external sounds.
• Heightened sensitivity in the auditory pathways can alert the brain to normal noise in blood vessels in much the same way that the awareness of non-pulsatile tinnitus is generated.
Miscellaneous
Some causes of pulsatile tinnitus do not fall into any of the above categories. In particular, there is a condition called benign intracranial hypertension, also known as idiopathic intracranial hypertension or pseudotumor cerebri. This is characterised by headaches and visual disturbance as well as pulsatile tinnitus. It is said to occur most frequently in overweight young or middle aged women. However, it can occur at any age and in men as well as women. Its cause remains unknown.
It is important to state that this is not an exhaustive list of the causes of pulsatile tinnitus and that anyone with this symptom should seek assessment by an appropriate doctor.
Source: British Tinnitus Association
