The vast majority of patients with hearing loss need only an audiogram to confirm the diagnosis. As stated earlier, most of these patients will be diagnosed with diseases limited to the inner ear such as presbycusis, noise-induced hearing loss, and ototoxicity. Asymmetry in hearing loss warrants the performance of magnetic resonance imaging (MRI) scan with paramagnetic enhancement to rule out a retrocochlear etiology.
In the pediatric patient with unilateral sensorineural hearing loss, a CT scan is warranted to rule out a bony malformation of the inner ear. A young patient with bilateral hearing loss should undergo genetic testing for Connexin 26 (GJB2) mutations. Other tests that have been advocated in the workup of pediatric patients for sensorineural hearing loss include urinalysis (Alport), electrocardiogram (EKG) (Jervell and Lange-Nielsen), thyroid function tests (Pendred), and electroretinography (Usher). Newer studies question the cost-effectiveness of ordering these tests in the absence of other history or physical findings implicating these syndromes.
A small fraction of adult patients will present with symptoms of hearing loss that warrant further investigation. Unfortunately, our testing options remain limited and often rely on circumstantial evidence. Patients with sudden unilateral sensorineural hearing loss require an audiogram and an MRI scan. Further testing is usually not warranted.
Patients with rapidly progressive sensorineural hearing loss (evolving over weeks to months), be it unilateral or bilateral, require a workup for autoimmune disease and syphilis. The screening tests have not been standardized and vary somewhat between sites. Our screening evaluation typically involved obtaining complete blood count (CBC), sedimentation rate, electrolytes, blood urea nitrogen (BUN), creatinine, urinalysis, antinuclear antibody (ANA) screen, rheumatoid factor, anti-Sjögren's antibodies, C3 & C4 levels, antinuclear cytoplasmic antibody (c-ANCA), antiphospholipid antibody screen, Lyme titers, and fluorescent treponemal antibody-absorption test (microhemagglutination assay for antibodies to T. pallidum) (FTA-ABS [MHA-TP]). Western blot for heat-shock protein 70 (HSP-70) may be supportive of a diagnosis of "autoimmune" steroid-responsive sensorineural hearing loss. In our screening of over 300 patients with progressive, idiopathic sensorineural hearing loss, only ANA levels (in bilateral disease) and antipho-spholipid antibodies have shown any significant elevations. Patients with very rapidly progressive bilateral sensorineural hearing loss (evolving over days to weeks) should also undergo a lumbar puncture, for analysis of CSF for infection and malignancy.
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