What is acoustic neuroma and how is it related to hearing loss?
Hearing loss can occur due to genetic or non-genetic reasons. However, acoustic neuroma or vestibular schwannoma, is one of the causes of non-genetic hearing loss. It is a slow-growing benign tumor that develops within the balance and hearing nerves in the inner ear. The tumor occurs due to overproduction of the Schwann cells. Due to overproduction, the cells surround the nerve fibers to support themselves.
How does acoustic neuroma affect hearing?
When the acoustic neuroma starts to grow, it presses against the hearing and balance nerve. The pressure blocks the signal pathways of the nerve resulting in unilateral or asymmetrical hearing loss, tinnitus (ringing in the ears) and dizziness.
Hearing loss is usually one of the first symptoms of acoustic neuroma. In the past, up to 90 percent of the patients diagnosed with acoustic neuroma reported a problem with their hearing. It starts with patients not being able to hear conversations in public settings and gradually leads to partial hearing loss.
Several older adults experience a diminished hearing sense with the passage of time. They usually experience hearing loss in both the ears. With acoustic neuroma, the patient feels a loss of hearing in one ear more than the other. If this is the case, then the patient should refer to a doctor. However, it is quite difficult to detect the problem as the hearing loss occurs gradually and patients rarely feel pain. In addition, only five percent of people experience sudden hearing loss.
How to Detect Acoustic Neuroma?
You can easily detect acoustic neuroma through the following tests:
- Pure tone average (PTA): this measures different levels of hearing frequencies in individuals. The patient wears earphones and listens to different tones of about 8 frequencies. If patients are able to hear the sound, they indicate it by pressing a button. An average of the results is then taken to determine the PTA score (the higher the score, the worse the hearing).
- The speech reception threshold (SRT): much like PTA, the SRT is partially different since it measures the lowest thresholds only. Similarly, the higher the SRT, the worse the hearing.
- Speech discrimination (SD): this tests the number of spoken words the patient can recognize. The patient wears earphones while words are repeated several times in one ear. The patient is then asked to recognize them. The lower the SD score, the worse the hearing
Hearing loss occurs when auditory nerves are compressed or infiltrated. As the tumor increases in size, it puts pressure on the nerves by pressing against them. This disrupts the pathway of sound, making the pathway lose its clarity. Sometimes, the tumor presses against the blood vessels and creates an obstruction in the blood supply to the inner ear. The tumor grows slowly and so the hearing loss also occurs gradually, which eventually leads to total deafness in the ear that contains the tumor.