What is pulsatile tinnitus?
Tinnitus is the awareness of sound by a patient in the absence of an appropriate external source. Pulsatile tinnitus is a symptom that relates to any condition causing a person to hear a sound synchronously with their own heartbeat. Pulsatile tinnitus usually has a source and is, therefore, an appropriate awareness by the patient. In most cases, the pulsatile tinnitus or bruit is caused by a vascular problem, not an ear problem.
Tinnitus and hearing loss.
Tinnitus is often accompanied by hearing loss, but not all patients with hearing loss suffer from tinnitus. A patient should have an adequate hearing to perceive the pulsatile tinnitus. Pulsatile tinnitus can also cause hearing loss, with an improvement of hearing when the tinnitus is treated.
The significance of pulsatile tinnitus?
Pulsatile tinnitus can be really annoying, causing a lot of distress to patients. Patients are often concerned that there is something about to “burst” or “blow up” in their head. Although this condition is usually not life- threatening, in some cases it may be associated with a serious condition and therefore always require investigation. Pulsating rarely resolves on its own.
What causes pulsatile tinnitus?
Numerous conditions may be responsible for pulsating tinnitus. The mechanisms by which it can occur include:
- The acceleration of blood flow which disrupts the normal laminar flow, converting it into audible turbulent flow.
- The amplification of normal sounds due to conditions of the inner that increase bone conduction.
- The impairment of sound conduction leading to reduced masking of external sounds.
- A hyperdynamic circulation.
One of the most underdiagnosed and common causes of pulsatile tinnitus is venous sinus stenosis.
What is venous sinus stenosis?
Venous sinus stenosis is one of the most underdiagnosed causes of pulsatile tinnitus.
The venous sinuses within the skull are venous channels filled with blood that drain the brain’s blood and transport it via the large neck veins to the heart. Venous sinus stenosis is a narrowing in any of these sinuses. When significant to influence blood flow, it may lead to pulsatile tinnitus. One of the most common stenosis mechanisms is the enlargement of arachnoid granulations or valves found in the venous sinus walls. These valves regulate the flow of cerebrospinal fluid (CSF) into the venous sinuses. The reason for this enlargement is not known.
The affected venous sinuses are near the ear and therefore easy to hear.
The association between idiopathic intracranial hypertension and venous sinus stenosis.
Idiopathic intracranial hypertension (IIH) is a condition of unknown origin characterised by an increase in the skull’s pressure. It may present with pulsatile tinnitus, visual disturbances and headaches.
More common in younger female patients, obesity is often a co-morbid finding. In many cases patients with IIH only present with pulsatile tinnitus which may lead to IIH being missed in patients with venous sinus stenosis.
Venous sinus stenosis decreases blood drainage from the brain. Therefore, the draining of cerebrospinal or brain fluid into the venous sinuses may increase intracranial pressure. In some patients with venous sinus stenosis, IIH may be present.
How is venous sinus stenosis diagnosed?
Patients will usually present with pulsatile tinnitus on one side. Patients can often manipulate the loudness of the tinnitus by utilising different manoeuvres, including turning of the head, Valsalva manoeuvres, and compression of either side of the neck. When gentle compression on the same side quiets the noise, it is highly suggestive of a venous disorder of which venous stenosis is a common and often underdiagnosed cause.
Subjective tinnitus is tinnitus that can only be heard by the patient himself. Objective pulsating tinnitus can be heard by other persons, but emphasising this is not so important and depends on the observer’s hearing ability or if a stethoscope is used in the examination. The noise may sometimes be heard on the opposite side. Not being able to hear a sound with a stethoscope does not rule out venous sinus stenosis.
Confirming venous sinus stenosis.
The examination of choice is contrasted magnetic resonance imaging (MRI) with specific protocols to evaluate blood flow in the venous sinuses. The specialists best equipped to perform these investigations are radiologists.
How is venous sinus stenosis treated?
After all other treatable conditions that may contribute have been addressed, and the patient is still symptomatic venous sinus stenosis can be managed by placing a stent in the stenosed segment. A conventional angiogram performed by a neuro-interventional radiologist will have to be performed to accurately place the stent.
What should I do when I suspect that I may have venous sinus stenosis?
It is advised to see an ENT surgeon exclude any other treatable causes of pulsatile tinnitus. Ask the ENT about venous sinus stenosis and request a referral to an interventional neuro-radiologist when in doubt. There are also support groups for sufferers of pulsatile tinnitus. Visit www.whooshers.com for more information on such a support group.
