The purpose is exclusively to provide amplification with less feedback and not specifically awareness of sounds from the unaidable ear.
It is presumed that moving the hearing aid microphone to the other side of the head from the aided ear will allow greater headroom in the fitting before the onset of acoustic feedback. Power CROS - a special case of the wired or wireless CROS.Transcranial - One completely dead ear and one ear that is either normal or has at most a mild high frequency hearing loss.Wired & Wireless - One unaidable ear and one ear that is either normal or has at most a mild high frequency hearing loss.The Power CROS is the only exception to this rule. The signal is routed to a normal hearing ear and therefore amplification is undesirable. CROS - used exclusively to provide awareness and audibility of sounds from the side of the unaidable ear (Ericson, Svard, & Hogset, 1988).If I do not regularly find myself in situations where my performance is compromised by my unaidable ear, I will not have the proper motivation to succeed with a CROS or BiCROS instrument. In other words, it does not matter how perfect a textbook example of the appropriate hearing loss I may have. That motivation typically stems from the recognition of one or more listening situations where performance is compromised by their inability to attend to signals from the side of the unaidable ear. For this reason, regardless of the hearing loss configuration, any CROS/BiCROS fitting is doomed to fail unless the wearer is motivated to make it succeed. Motivation - These systems all include some element of inconvenience beyond that of a traditional hearing aid.However, here is a short outline to use as a quick reference. Appropriate candidacy and the expected benefits of each type of fitting have been described elsewhere (Hayes, Pumford, & Dorscher, 2005 Sandlin, 1994). BiCROS devices are limited to wired and wireless air conduction hearing aids as transcranial fittings do not readily lend themselves to BiCROS applications. They will be discussed as one type of fitting with the distinctions between them being mentioned where appropriate. For the most part, the challenges of fitting wired and wireless CROS aids are about the same. As mentioned above, this guide is most applicable for clinicians who do not fit CROS/BiCROS systems on a frequent basis.ĬROS devices can be placed into one of three categories: wired, wireless and transcranial (Ericson, Svard, & Hogset, 1988 Hayes, 2001 Hayes & Chen, 1998 Hayes, Pumford, & Dorscher, 2005 Pumford, 2005). It has been written in outline form as a clinical aid to help the reader quickly locate sections that are relevant for a specific fitting. It begins with a statement of the goals for each type of fitting followed by a brief set of evaluation instructions and concludes with a selection of tips, tricks and traps. If this describes your caseload, this paper has been written for you. These types of cases are seen so infrequently that clinicians may not be at ease when fitting or evaluating them. They may practice these fittings on a weekly or monthly basis and consequently they have developed their own system for testing them.Ĭonsequently, most clinicians may see as few as two to four people in an entire year who have one truly unaidable ear. Clinicians who work in such facilities often have considerable expertise in fitting and assessing Contralateral Routing of Signal (CROS) and Bilateral CROS (BiCROS) hearing aid fittings. In general, the term "unaidable" is used here to mean an ear for which no form of amplification, air conducted or bone conducted, will provide any meaningful benefit. The clinical populations of such groups are often skewed toward a larger than average subset of individuals who have "unaidable" unilateral hearing loss (Sandlin, 1994). There are Audiology groups in most large urban centers affiliated with teaching hospitals or large scale otolaryngology services.
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