This is probably more than you want to know. Pulsatile tinnitus can be serious – see below. It may require evaluation by a specialist. The source of this information is “Up to Date.” “Up to Date” is a medical subscription service. Look at area surrounded by”*****” below.
UpToDate performs a continuous review of over 350 journals and other resources. Updates are added as important new information is published. The literature review for version 14.1 is current through December 2005; this topic was last changed on August 5, 2004. The next version of UpToDate (14.2) will be released in June 2006.
INTRODUCTION — Tinnitus is a perception of sound in proximity to the head in the absence of an external source. It can be perceived as being within one or both ears, within or around the head, or as an outside distant noise. The sound may be a buzzing, ringing, or hissing, although it can also sound like other noises.
Tinnitus can be characterized as continuous (a never ending sound) or intermittent. Although both may have a significant impact on the patient, the latter is not usually related to a serious underlying medical problem.
EPIDEMIOLOGY — According to the American Tinnitus Association, an estimated 50 million people in the United States have tinnitus . For 12 million, it is severe enough to interfere with daily activities. These people are effectively disabled by their tinnitus to varying degrees. Even in patients who do not report limitations, tinnitus can be distracting and can have an impact upon quality of life.
Tinnitus is more common in men than women and the prevalence increases with age .
ETIOLOGY/PATHOGENESIS — Tinnitus can be triggered anywhere along the auditory pathway (show table 1 and show figure 1). It is believed to be encoded in neurons within the auditory cortex. Somatic sounds also can be perceived as tinnitus.
Somatic sounds — Somatic sounds that are perceived as tinnitus originate in structures with proximity to the cochlea. These sounds can be generated in vascular structures or may be produced by musculoskeletal structures.
Vascular tinnitus can be constant but is most commonly pulsatile. Vascular etiologies include venous hum, vascular tumors (eg, glomus tumor), arteriovenous malformations, increased intracranial pressure, and arterial flow abnormalities.
Clicking noises or irregular or rapid pulsations are often the result of myoclonus of the palatal muscles that attach to the eustachian tube orifice, or of the muscles and tendons of the middle ear. Idiopathic myoclonus of the palatal muscles is rare; most often an underlying neurologic abnormality accompanies such findings, and the history and physical examination should include a search for other neurologic disease.
In a retrospective review of 84 patients with pulsatile tinnitus seen in a neurology department, 42 percent were found to have a significant vascular disorder (most commonly a dural arteriovenous fistula [AVF] or a carotid-cavernous sinus fistula) . In 12 patients (14 percent), nonvascular disorders such as glomus tumor or intracranial hypertension with a variety of causes explained the tinnitus.
Vascular disorders — As mentioned, a number of vascular disorders can cause tinnitus that may be suspected when the patient complains of a pulsatile or varying tinnitus.
Arterial bruits may be transmitted to the ear from arterial vessels near the temporal bone; the patient hears the turbulent blood flow, especially if the loudness of the sound exceeds the hearing threshold in that ear. The petrous carotid system is the most common source, although other arteries may also be involved . Most of these patients have tinnitus symptoms that are greatest at night, and usually do not have other otologic complaints (eg, hearing loss, vertigo, aural fullness).
Venous hums may be heard in patients with hypertension (either systemic or intracranial hypertension due to pseudotumor cerebri), or in patients with a dehiscent or dominant jugular bulb (abnormally high placement of the jugular bulb). The latter may also cause a conductive hearing loss. Tinnitus in patients with a venous hum is often described as a soft, low-pitched hum that may decrease or stop with pressure over the jugular vein, with a change in head position, or with activity .
Congenital arteriovenous shunts are rarely associated with hearing loss or tinnitus, while acquired arteriovenous shunts are often symptomatic. The latter may be caused by penetrating trauma, surgery, or a tumor.
Glomus tumor is a vascular neoplasm arising from the paraganglia found around the carotid bifurcation, the jugular bulb, or the tympanic arteries. These tumors commonly cause a loud pulsing tinnitus that may interfere with hearing. The lesion may be visible through the tympanic membrane as a reddish or blue mass, or may be palpable in the neck. As the tumor enlarges, it may cause hearing loss because of impingement on the ossicular chain (conductive loss) or the labyrinth or cochlea (sensorineural loss). Other cranial nerves may also be effected (eg, facial nerve or lower cranial nerve palsies.)
Neurologic disorders — Pulsatile tinnitus of muscular origin can be seen with spasm of the two muscles that act within the middle ear (the tensor tympani and the stapedius muscle). Such muscle spasms occur spontaneously, because of local otologic disease, and in the presence of a neurologic disease such as multiple sclerosis. Patients may also complain of hearing loss or aural fullness. Tympanometry and otoscopy can be particularly useful in diagnosing middle ear spasmodic activity.
Eustachian tube dysfunction — A patulous eustachian tube can cause tinnitus with sounds similar to an ocean roar that may be synchronous with respiration . It most commonly occurs after significant weight loss or after external beam radiation to or near the nasopharynx. The symptoms may disappear when the patient lies down. Patients can also complain of an unusual awareness of their own voice (autophony). The cause of these symptoms is a eustachian tube that remains abnormally patent, allowing too much and then too little aeration of the middle ear space with respiration…….
Suspected vascular tinnitus — Patients with infrequent episodes of pulsatile tinnitus or those with short duration, mild tinnitus can be initially observed. However, because pulsatile tinnitus can herald a potentially life-threatening illness, all of these patients require an evaluation by an otolaryngologist or neurotologist.
When patients complain of constant (non-episodic) pulsatile tinnitus and the physical examination does not reveal a specific vascular or musculoskeletal source, further investigation to rule out a central nervous system (CNS) lesion such as a dural arteriovenous fistula (AVF) or a skull base tumor should be carried out. The gold standard for AVF diagnosis is angiography. These lesions often can also be diagnosed noninvasively with MR angiography . CT scanning is required to delineate the extent of involvement of the skull-base if a glomus tumor is suspected and may be sufficient to evaluate other CNS lesions in selected patients. MRI can be used to diagnose a Chiari malformation and can indicate the presence of an increased intracranial pressure (such as that seen in pseudotumor cerebri), or tumors. Many patients require both MRI and CT because of the varied nature of disorders that cause pulsatile tinnitus. If both of these contrast studies are normal, and suspicion remains high, angiography or MR angiography is warranted.
Positron emission tomography (PET) has been able to pick up abnormal blood flow in the auditory cortex in animal tinnitus models and can be used to follow changes in the CNS following tinnitus treatments. However, PET scanning currently has limited utility as a clinical diagnostic tool.
Single photon emission tomography (SPECT) imaging may be more clinically useful. SPECT imaging shows not only dynamic changes within the brain at the neurotransmitter level, but can sometimes be more sensitive than conventional brain imaging (CT scan, MRI or MR angiography) in identifying an anatomic or vascular anomaly . For these reasons, SPECT imaging may soon become a more widely used tool to evaluate tinnitus complaints
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