Tuesday, November 23, 2010

Your Audiology Tutorial: Auditory Processing Disorder, Part One

Certain people have difficulty with the processing of auditory information, attention strategies, and listening skills. It is not necessarily that their hearing acuity is impaired, but rather that there are complications with utilizing auditory input in a useful manner. A patient with an auditory processing disorder (APD) will often be easily distracted by visual stimuli, unable to follow a complex set of directions given orally, and very frustrated with sound degraded environments (especially noisy places).

Again, the above difficulties can occur in the absence of a hearing loss. Many patients with APD have hearing sensitivity within normal limits. I described the noisy environment; a majority of patients with hearing loss struggle with speech intelligibility as their inner ears have become damaged due to aging, noise exposure, medications, etc. Auditory figure ground refers to an analysis involving an APD patient who struggles with background noise, such as in a classroom or anywhere where there are multiple talkers and sounds. Rallying attention and focus is difficult. To note, my example suggests that most diagnosed cases of APD are for children.

Referrals for auditory processing evaluations (APE), a battery of tests we will overview shortly, often come from school instructors who note that the patient may have problems with the aforementioned as well as with reading, phonics, spelling, the amount of time needed to accomplish these tasks, and so on. After a case history is taken, many times it will be revealed that the patient does not have a positive history for fluid in the ears, delay of development milestones, or other medical insult.

The subtests in the APE typically include:

1. Dichotic Digits: an assessment of divided auditory attention which measures the patient's response patterns concerning the neuromaturation of the auditory nervous system and the transfer of auditory information between the brain's two hemispheres. Two numbers are played simultaneously in each ear and the patient is instructed to repeat either those heard in the right or left ears at given times. How developed a patient's binaural integration (divided auditory attention)is is measured by the percentage of digits correctly identified in each ear.

2. Frequency Pattern Test: Measures the ability to recognize the prosody (meaning of words denoted by stress pattern) of speech, including timing and intonation. Tones are played and the patient responds by describing the pitch of a triplicate series ("high-low-high", etc.). Sometimes, the patient will be asked to hum back the pitches. Identifying these auditory patterns is another test of interhemispheric transfer, or how the two sides of the brain work together to process inputs.

3. A test which measures the ability to discern a target phrase or sentence is the Competing Centences test. Simultaneously, a sentence is read into each ear; the patient is asked to either identify the one in the right or left ear. The assessment here is again of focused auditory attention, or binaural separation. Percentage scores are calculated based on correct responses per ear. A delay in binaural separation may be discerned by a low score for an ear.

In Part Two, we will examine some of the other subtests typically administered as well as what suggestions may be made by the clinician to the patient, family members, teachers, and others involved in designing a treatment plan.

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