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Chapter 212 Evaluation of Hearing Loss
chemotherapeutics, and the loop diuretics furosemide and ethacrynic acid. A history of otitis, noise exposure (both rec reational and work related), or head trauma should be noted. Inquiry into noise exposure is important, especially the details of occupational exposure. Family history is no less important, particularly in the consideration of gene mutations, otosclerosis, and acoustic neuromas (associated with von Reck linghausen disease). Physical Examination The external auditory canal should be inspected for obstruction by impacted cerumen, a foreign body, external otitis, or exosto ses. The tympanic membranes are examined for inflammation, perforation, and scarring. One notes any fluid in the middle ear, although, depending on the state of the tympanic membrane, accurate detection of middle ear fluid may be challenging even for experienced clinicians. A bluish or reddish mass visible through the intact tympanic membrane may indicate a high-riding jugular bulb, an aberrant internal carotid artery, or a glomus tumor. Pneu matic otoscopy assesses tympanic membrane mobility and helps to discern the presence or absence of middle ear fluid. Nasopharyngeal examination is indicated in patients with persisting serous otitis media, particularly if it is unilateral. If there is vertigo or suspicion of a glomus or acoustic tumor, cra nial nerve examination is performed to assess central nervous system involvement (see Chapter 166). If the history and physical examination are otherwise normal and unrevealing in the face of an abrupt onset of hearing loss and the patient complains of a unilateral “blockage” (i.e., hear ing loss), the clinician should suspect the diagnosis of sudden idiopathic sensorineural hearing loss, which requires expedi tious referral to an otolaryngologist for further evaluation, audiometry, and possible therapy with high-dose corticoste roids (see Table 212-3). Testing of Hearing The watch tick was an easy, although crude, method of detect ing high-frequency impairment when ticking watches were common. Whispering , gradually increasing the intensity of the whisper, is readily performed. One asks the patient to repeat a number of words whispered into the tested ear while masking the contralateral ear (e.g., with a Barany noise box or manual occlusion of the contralateral external auditory canal). The best words are familiar bisyllabic ones in which both syllables are equally accented (e.g., pancake, hot dog). With practice, one can roughly estimate the patient’s hearing thresholds. Differentiating Conductive from Sensorineural Hearing Loss The Weber test is helpful. The normal response to a fork vibrat ing from a tap of the knee and placed midline on the skull is equal loudness in both ears. If there is a conductive loss, the sound will be heard more clearly in the ear with the loss. If there is a sensorineural loss in one ear, sound will be perceived as being heard in the better ear. The Rinne test complements Weber testing. When the vibrat ing fork is placed on the mastoid process, it is heard for a period of time and then dies away. It is heard again if the same fork is promptly moved without any reactivation to the external auditory canal. Normally, sound conducted by air is heard about twice as long as a sound conducted by bone because of the greater sound transmission efficiency of the middle ear apparatus. Alternatively, with firm application of the tuning fork against the mastoid process for a few seconds and immediate transfer to the external auditory canal, the sound should be perceived as “louder” in front of the canal when compared with the mastoid position.
With a substantial (generally ≥ 25 dB) conductive loss, the ratio reverses. With lesser degrees of impairment, the ratio approaches 1:1. The normal ratio is preserved in sensorineural losses. The Schwabach test compares the examiner’s hearing by bone conduction with that of the patient’s. The vibrating tuning fork is alternately placed on the mastoid process of examiner and patient. If the examiner’s hearing is normal, he or she will perceive the sound for a longer time than the patient with a sensorineural deficit and for a shorter time than the patient with a conductive problem. Focal Neurologic Exam A focused neurologic examination helps detect any associated central or vestibular system pathology, differentiating serious underlying pathology from more benign disease. Instruct ing the patient to keep gaze fixed on a target while passively rotating the head sinusoidally from side to side and up and down helps assess cranial nerves III, IV, and VI, brainstem, and cerebellum. Testing the face for light touch and pinprick checks cranial nerve V, while asking the patient to mimic facial expressions tests VII. Checking for nystagmus, spontaneous, gaze evoked, or positional, helps assess cranial nerve VIII, cer ebellum, and brainstem. Cerebellar function is also examined by observing extremity coordination, postural and gait stability, and rapidly alternating movements, facilitated by Romberg and tandem gait testing. Table 212-3 A Clinical Practice Guideline for Sudden Idiopathic Sensorineural Hearing Loss from the American Academy of Otolaryngology— Head and Neck Surgery STATEMENT 1. EXCLUSION OF CONDUCTIVE HEARING LOSS: Clinicians should distinguish sensorineural hearing loss (SNHL) from conductive hearing loss (CHL) in a patient presenting with sudden hearing loss. STATEMENT 2. MODIFYING FACTORS: Clinicians should assess patients with presumptive sudden SNHL for bilateral sudden hearing loss, recurrent episodes of sudden hearing loss, or focal neurologic findings. STATEMENT 3. COMPUTED TOMOGRAPHY: Clinicians should not order computerized tomography of the head/brain in the initial evaluation of a patient with presumptive SSNHL. STATEMENT 4. AUDIOMETRIC CONFIRMATION OF ISSNHL: Clinicians should diagnose presumptive ISSNHL if audiometry confirms a 30-dB hearing loss at three consecutive frequencies and an underlying condition cannot be identified by history and physical examination. STATEMENT 5. LABORATORY TESTING : Clinicians should not obtain routine laboratory tests in patients with ISSNHL. STATEMENT 6. RETROCOCHLEAR PATHOLOGY: Clinicians should evaluate patients with ISSNHL for retrocochlear pathology by obtaining an MRI, auditory brainstem response (ABR), or audiometric follow-up. STATEMENT 7. PATIENT EDUCATION: Clinicians should educate patients with ISSNHL about the natural history of the condition, the benefits and risks of medical interventions, and the limitations of existing evidence regarding efficacy. STATEMENT 8. INITIAL CORTICOSTEROIDS: Clinicians may offer corticosteroids as initial therapy to patients with ISSNHL. ISSNHL, idiopathic sudden sensorineural hearing loss. Adapted from Stachler RJ, Chandrasekhar SS, Archer SM, et al. Clinical practice guideline: sudden hearing loss. Otolaryngol Head Neck Surg 2012;146:S1. Copyright © 2011, Official Journal of the American Academy of Otolaryngology—Head and Neck Surgery Foundation.
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