Tinnitus is defined as the perception of sound in the absence of an acoustic stimulus. Tinnitus, a subjective experience of the patient, is distinguished from bruit, noise that may be heard by the examiner and often by the patient as well.
Tinnitus may be of a buzzing, ringing, roaring, whistling, or hissing quality or may involve more complex sounds that vary over time. It may be intermittent, continuous, or pulsatile (synchronous with the heartbeat). An associated hearing loss is usually present.
The mechanism involved in tinnitus remains obscure. Tinnitus may occur as a symptom of nearly all ear disorders, including obstruction of the external auditory canal as a result of cerumen or foreign bodies, infectious processes (external otitis, myringitis, otitis media, labyrinthitis, petrositis, syphilis, meningitis), eustachian tube obstruction, otosclerosis, middle ear neoplasms such as the glomus tympanicum and glomus jugulare tumors, MeniereÕs disease, arachnoiditis, cerebellopontine angle tumors, ototoxicity (due to salicylates, quinine and its synthetic analogs, aminoglycoside antibiotics, certain diuretics, carbon monoxide, heavy metals, alcohol, etc.), cardiovascular diseases (hypertension, arteriosclerosis, aneurysms, etc.), anemia, hypothyroidism, hereditary sensorineural or noise-induced hearing loss, acoustic trauma (blast injury), and head trauma.
Evaluation of the patient with tinnitus begins with a comprehensive audiologic assessment as well as CT of the temporal bone and MRI of the head. Pulsatile tinnitus requires investigation of the vascular system with carotid and vertebral arteriograms to exclude arterial obstruction, aneurysms, and vascular neoplasms.
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