[Differential diagnosis of unilateral hearing loss]

There are two main kinds of hearing disorders: sensorineural and conductive. Sensorineural hearing loss is a common disorder that results from damage to the inner ear in over 95% of all cases; therefore, retrocochlear hearing disorders are rare and cannot be differentiated from sensory losses by clinical symptoms alone. Unilateral hearing loss entails many problems in hearing during the entire life of the affected patients. Conductive deafness has a readily determined etiology in most cases. In contrast, unilateral sensorineural hearing loss requires more refined and extensive investigation. The etiology of an asymmetric sensorineural hearing loss can often be difficult to determine. Because a wide variety of pathologic processes may be responsible for the hearing loss, numerous diagnostic tests are usually used during initial evaluation, including pure-tone audiometry, acoustic reflex testing, imaging, serologic testing, and auditory brainstem response testing. The most frequent causes of unilateral sensorineural hearing loss were sudden deafness, Menière's disease and cerebellopontine angle tumors. Early diagnosis of acoustic neuroma or other lesions of the internal auditory meatus or cerebello-pontine angle requires special attention. The patient with an acoustic neuroma may present to the otologist with a variety of clinical features. Classically these include a retrocochlear pattern of sensorineural hearing loss, reduced vestibular response on caloric testing and a pathological auditory brainstem response. Magnetic resonance imaging offers greater specificity than computed tomography. Therapy of unilateral sensorineural hearing loss includes efforts to treat known causes either medically or surgically.