A 56-year-old previously healthy man comes to the office due to decreased hearing in both ears. He reports difficulty understanding conversations in crowded rooms. His wife adds that they often argue about the volume of the television set. The patient cannot remember precisely when he first noticed hearing loss but says it has been present at least 6 months and is getting worse. For the past 12 years, he has worked in a factory where he has to shout to communicate with coworkers and has seldom worn hearing protection. An audiogram is obtained as shown in the image below. Which of the following is most likely abnormal in this patient?

Question

A 56-year-old previously healthy man comes to the office due to decreased hearing in both ears.  He reports difficulty understanding conversations in crowded rooms.  His wife adds that they often argue about the volume of the television set.  The patient cannot remember precisely when he first noticed hearing loss but says it has been present at least 6 months and is getting worse.  For the past 12 years, he has worked in a factory where he has to shout to communicate with coworkers and has seldom worn hearing protection.  An audiogram is obtained as shown in the image below.  Which of the following is most likely abnormal in this patient?

Quizplus · Accepted Answer

11ec160b_356d_0105_9249_09a3d3f90893_MD0001_00 This patient has high-frequency hearing loss due to chronic noise exposure. Transduction of mechanical sound waves into nerve impulses occurs in the organ of Corti through the following steps: Noise-induced hearing loss results from trauma to the stereociliated hair cells of the organ of Corti. The acoustic reflex normally dampens the effects of loud noise by causing the stapedius and tensor tympani muscles to contract, which lessens the responsiveness of the ossicles to sound. However, prolonged noise exposure can cause distortion or fracture of the stereocilia due to shearing forces against the tectorial membrane. High-frequency hearing is lost first, regardless of the frequency of the sound causing the damage. (Choice A) Hearing loss originating in the auditory nerve is most commonly due to a vestibular schwannoma (acoustic neuroma). Patients develop high-frequency sensorineural hearing loss, but symptoms are usually unilateral. (Choice B) The cochlear cupula is the apex of the cochlea and is distant from the oval window. The distal cochlea primarily registers low-frequency sound. (Choice C) Defects of the middle ear ossicles (eg, otosclerosis) can cause hearing loss that generally affects air conduction across all frequencies. This patient's hearing loss affects both air and bone conduction. (Choice E) The round window lies between the middle and inner ear and moves outward when the stapes causes the oval window to move inward. Malformation of the round window can cause congenital hearing impairment, but acquired disorders are rare. (Choice F) Perforation or rupture of the tympanic membrane can occur with infection, trauma, pressure changes, or sudden and very loud noises. Rupture of the tympanic membrane causes unilateral conductive hearing loss. Educational objective: Prolonged exposure to loud noises causes hearing loss due to damage to the stereociliated hair cells of the organ of Corti. __________ References: Hearing impairments caused by genetic and environmental factors. (http://www.ncbi.nlm.nih.gov/pubmed/22899349)

A 56-Year-Old Previously Healthy Man Comes to the Office Due