19 Tinnitus

Eric L. Slattery, Timothy E. Hullar, and Lawrence R. Lustig

Tinnitus is an extraordinarily common condition, yet its etiology is not well understood. Present theories posit that inner ear hypofunction decreases input to the auditory nerve, leading to a form of neural plasticity manifest as a compensatory hyperactivity or upregulation of central nuclei of the ascending auditory pathways.

Tinnitus may be unilateral, bilateral, or not localized. It may be pulsatile or nonpulsatile. Pulsatile tinnitus may be objective, in that a clinician can auscultate a bruit, or subjective. Most often there is no definable cause, and in cases for which a cause can be defined, there is often no intervention that leads to a cure. The most common form of tinnitus, which is nonpulsatile and subjective, usually presents in a healthy patient with a benign examination who may or may not have some degree of hearing loss. There is a strong correlation between chronic tinnitus and a diathesis of depression.

image Objective, Vascular, and Pulsatile Tinnitus

Objective tinnitus may be heard by the examiner, although it is not a requirement for the diagnosis. Most objective tinnitus is classified as either arterial or venous. Venous tinnitus can be decreased with pressure to the internal jugular vein, whereas arterial tinnitus is unchanged by this maneuver.

Carotid Bruit

Pulsatile tinnitus can arise from bruits transmitted from the carotid artery. Often it is simply a transmitted flow murmur. Auscultation of the neck can suggest the diagnosis.

Aortic Valve Bruit

Pulsatile tinnitus can arise from bruits transmitted from the cardiac aortic valve with organic valvular disease. Auscultation of the thorax can suggest the diagnosis.

Dural Arteriovenous Malformation

Approximately 15% of intracranial arteriovenous malformations (AVMs) are dural. Pulsatile tinnitus reported by patients with dural AVM is arterial and often worse at night. Dural AVM is thought to be acquired following sinus thrombosis, most commonly in the transverse and sigmoid sinuses. Usually, a loud bruit is audible over the involved sinus. Patients may present with other neurologic manifestations if cortical hypertension results secondary to the AVM. Sudden change in tinnitus may herald impending cortical hypertension following venous outflow thrombosis.

Glomus Tumors

Pulsatile tinnitus caused by a paraganglioma may be due to glomus tympanicum or glomus jugulare tumors. Tinnitus is classically unilateral, and patients may also have a conductive hearing loss. A tumor found on the cochlear promontory may be seen behind the tympanic membrane as a purplish mass on otoscopy. If the lesion is a glomus jugulare, additional jugular foramen symptoms may be present, including hoarseness, dysphagia, aspiration, and vocal cord paresis. Computed tomography (CT) and magnetic resonance imaging reveal a middle ear lesion in the case of a glomus tympanicum, and in the case of a jugulare, erosion into the jugular bulb and often beyond.

Benign Intracranial Hypertension (Pseudotumor Cerebri)

Benign intracranial hypertension is often seen in overweight women. Tinnitus, along with hearing loss, has been reported as presenting symptoms for benign intracranial hypertension. More common symptoms are headache and blurred vision. Tinnitus often can be auscultated and is venous in origin. Both tinnitus and low-frequency hearing loss may be lessened with internal jugular vein compression. Papilledema is almost always present on physical examination. The pathophysiology is not well known, with poor absorption of cerebrospinal fluid likely. The differential diagnosis includes an intracranial mass, an AVM, and venous sinus thrombosis. Increased opening pressure with lumbar puncture is necessary to confirm the diagnosis.

image Objective, Vascular, and Nonpulsatile Tinnitus

Venous Hum

A venous hum is caused by turbulence in the sigmoid sinus or jugular vein; though not pulsatile, the sound may have a repetitive, machinelike quality. It often gets worse with head turns or in particular positions. Pressure on the jugular vein usually lessens the sound. Treatment is limited to observation and postural changes.

Dehiscent Jugular Bulb

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Jun 5, 2016 | Posted by in OTOLARYNGOLOGY | Comments Off on Tinnitus

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