“Perhaps one of the greatest mysteries in medicine is the brain and how it develops and changes. Even when supplied with the best information about sounds in our environment, our minds can play tricks. In some of my patients, the best strategies are just teaching patients to learn how to avoid the pitfalls since the comprehension of sound and language is the magic itself, not whether they heard something or not.”   - Drew Sutton, MD, Board-Certified Otolaryngologist

Modern diagnostics have come a long way in the past few decades as more research and emphasis are placed upon getting people to help sooner rather than later. This trend is evident in schools where screening for common learning disabilities is becoming more of an area of interest to ensure students are not left behind due to undiagnosed disabilities. 

One example is the recent dyslexia screenings being implemented in the Washington state education system. The early literacy screening provides those who would otherwise struggle with undiagnosed dyslexia an opportunity to get tailored assistance that allows them to have an easier time dealing with dyslexia and learn how to manage it effectively. 

Another disorder gaining more awareness in recent years is central auditory processing disorder (CAPD). While many instances of CAPD are now caught very early on in childhood or adolescence, several people slipped through the cracks and have been living with CAPD without even knowing it. 

Most research and energy with CAPD goes towards pediatrics since catching it early can lead to better outcomes, but adults diagnosed with CAPD lack available information, guidance, or screenings to help them. 

Below is a closer look at what CAPD is, how it affects listening ability, and strategies and tools that those with CAPD can utilize to have an easier time in their day-to-day life. 

Anatomy of Hearing

Hearing is a very complex process that involves moving parts, neurological impulses, and a network of neurons to make sense of it all. While we do not notice all of the work behind the scenes, it is a large undertaking, and the body does it seamlessly. 

Like any well-oiled machine, one issue could cost the entire process to falter. The same goes for hearing, as hearing impairment can occur at any point in the process. Below is a closer look at each step of hearing and hearing impairments associated with each step. Understanding how hearing works and how it can go awry is a significant step to understanding the differences between hearing impairments and auditory processing disorders. 

Outer Ear

The outer ear consists of the parts of the ear you can visually see. The outer ear consists of the outer structures of the ear and the ear canal. Both of these structures act to channel sound waves into the structure known as the eardrum. 

When looking at the outer ear in terms of hearing loss, there are not many things that can go wrong since it consists mainly of stationary structures. The only thing that could lead to a decreased hearing ability is a buildup of earwax in the ear canal. 

Over time earwax can accumulate and get to a point where it can block sound from adequately reaching the eardrum. Luckily with a good earwax extraction, hearing is normally restored. 

Middle Ear

The middle ear is a separate compartment from the outer ear separated by the tympanic membrane, also known as the eardrum. The middle ear consists of the tympanic membrane, the bones of the ear, the tympanic cavity, and eustachian tubes.

The middle ear works like a middle man by translating sound vibrations into the movement of small bones. This process is known as conduction and is an important aspect of hearing. When sound enters the ear canal, it reaches a dead-end known as the eardrum. When sound waves hit the tympanic membrane, it oscillates back and forth. 

The inner ear can be a large contributing factor to conductive hearing loss. With conductive hearing loss, any one of the structures above can be affected. One of the most notable is an ear infection where the tympanic cavity fills with fluid resulting in poor sound conduction, causing sounds to be more muffled and harder to hear. 

Other forms of conductive hearing loss can occur, such as a perforated tympanic membrane, but a common theme with all conductive hearing issues is that it has to do with a dysfunction in the middle or outer ear. 

Inner Ear

The inner ear is where sound is changed into neurological impulses. The inner ear bones are attached to the cochlea, a largely hollow structure internally lined with specialized hair structures. 

When the stapes vibrate the cochlea, a wave is sent through the cochlea. The hair associated with the characteristics of that specific wave relays the message towards the auditory nerve. There are thousands of different hairs in the cochlea that allow the human body to perceive a wide range of sounds. 

Problems with the inner ear result in what is known as sensorineural hearing loss. Sensorineural is caused by damage to the cochlea hairs or the auditory nerve leaving the ear. Sensorineural hearing loss is often permanent and results from overstimulation and damage to cochlear hairs. 

An example of a cause of sensorineural hearing loss is from those that work for extended periods in loud environments without ear protection. The result is constant stimulation of hairs in the cochlea that eventually can’t take it anymore and stop working properly. 

Brain Processing

The brain processing aspect of hearing is where all the hard work of conversing sound waves to nerve impulses pays off. Once the signal is sent out of the cochlea, it travels down the auditory nerve and goes into the brainstem, where the first stages of information processing occur. 

The signal then travels through other parts of the brain, consecutively processed until it reaches the auditory cortex.

One of the largest issues revolving around brain processing capabilities is central auditory processing disorder. Unlike other auditory impairments, CAPD has almost nothing to do with hearing a sound but rather understanding and differentiating one sound from another. 

Central Auditory Processing

Central auditory processing is a name for the process of auditory refinement and processing that the brain does to convey a sound. Processing includes some steps such as deciding what sounds matter, recognizing sound patterns, and much more. Propper central auditory processing allows you to carry out a conversation in a noisy crowd, locate the direction of where a sound originates, and understand verbal communication. 

Central Auditory Processing Disorder

CAPD is a condition where some aspect of the processing is not occurring as it should. As a result, it can be more difficult for those with CAPD to recognize certain sounds, locate the origin of a sound, or understand spoken language. 

In adults, CAPD can easily place a burden on quality of life. Frequently asking people to repeat themselves, having a hard time comprehending an individual in a loud environment, and frequently mishearing what someone has said can all be an annoyance. 

All of these symptoms are caused by errors due to processing rather than standard hearing loss. With CAPD, the sense of hearing can be completely intact; it is just that the ability to perceive the sound is altered. 

Tools for CAPD

CAPD is a long-term issue, and learning ways to cope with it can allow for it to have a lesser impact on your day-to-day life. Below is a closer look at some tools that can be utilized for those with a difficult time processing sounds. 

Captions

Captions have been around for decades, and at their most basic, they are a written transcript of the things being said. Today, there’s software that can convert verbal speech into written speech in real-time. Those with CAPD can understand others, but occasionally similar-sounding words can make it tricky for them to keep up with the pace of a conversation. 

Having real-time subtitles can significantly help those with CAPD ensure they are not missing out on the conversation. 

Hearing Aid

Another tool that can be utilized is a quality hearing aid. While hearing aids are typically used for hearing loss, some can be helpful for those with CAPD. Hearing aids such as the Audien EV3 contain technologies that can help to mitigate background noise while also amplifying the sounds of speech. 

For those with CAPD, reducing ambient noise and amplification of speaking can allow for an easier time comprehending and processing incoming speech. The EV3’s clear sound + technology can greatly improve sound quality and allow for a more isolated sound experience. 

Conclusion

In summary, central auditory processing disorder is an auditory impairment involving sound processing. Even though symptoms of CAPD can be similar to standard hearing loss, it is a distinct auditory impairment that has nothing to do with auditory acuity and more to do with how the information is processed and perceived in the brain. 

CAPD can be diagnosed at any point during your life, but many are caught early in life, allowing for earlier therapeutic intervention. CAPD diagnosis in adults is typically on the low side. Still, several different tools are available that can provide an easier time perceiving the world of sound around you. 

 

Sources:

Screening Tools and Best Practices | K12

Central Auditory Processing Disorder | ASHA

Anatomy and Physiology of the Ear | University of Rochester Medical Center