Abstract
Sickle cell disease (SCD) is an autosomal recessively inherited group of red blood cell disorders. It is more commonly found in African Americans and Hispanics in the United States. The sickle-shaped cells characteristic of the disease cause physiological problems, including hemolytic anemia and vaso-occlusion. Research has linked hearing loss to sickle cell disease. Studies have shown that children and adults with sickle cell disease may have higher rates of sensorineural and central auditory hearing impairment. This case study examines hidden hearing loss in an African American boy with SCD who presents with normal hearing thresholds. It also discusses the role of audiologists in the care of individuals with sickle cell disease and hearing loss.
Key Terms in this Chapter
Acoustic Reflexes: The acoustic reflex is an involuntary muscle contraction that occurs in the middle ear in response to high intensity sounds. When presented with a high intensity sound, the stapedius and tensor tympani muscles contract. The stapedius stiffens the ossicular chain by pulling the stapes (stirrup) of the middle ear away from the oval window of the cochlea, while the tensor tympani muscle stiffens the ossicular chain by pulling the malleus (hammer) in toward the middle ear. The reflex decreases the transmission of acoustic (mechanical) energy to the cochlea.
Auditory Brainstem Response (ABR): Auditory brainstem response (ABR) audiometry is a neurologic test of auditory brainstem function in response to auditory (click) stimuli. The ABR test provides information on how the inner ear, the cochlea, and the brain pathways for hearing are working.
Hydroxyurea: Hydroxyurea, a myelosuppressive agent, is the only effective drug proven to reduce the frequency of painful episodes in sickle cell disease. It raises the level of fetal hemoglobin (HbF). It usually decreases the rate of painful episodes by 50%. It was first tested in SCD in 1984. It was developed as an anticancer drug and has been used to treat myeloproliferative syndromes such as leukemia, melanoma, and ovarian cancer (CDC, 2019 AU50: The in-text citation "CDC, 2019" is not in the reference list. Please correct the citation, add the reference to the list, or delete the citation. ).
Sickle Cell Disease: Sickle cell disease is a group of autosomal recessively inherited red blood cell disorders. Red blood cells contain hemoglobin. People who have SCD have an abnormal protein in their red blood cells. The protein is called hemoglobin.
Vaso-Occlusive Crisis: A vaso-occlusive crisis occurs when microcirculation of blood vessels is obstructed by sickled red blood cells, causing ischemic injury to the organ supplied and resultant pain.
Hemoglobin: Hemoglobin is a protein found in red blood cells. It gives blood its red color, and its job is to transport and release oxygen throughout the body.
Prophylactic Penicillin or Antibiotics: Children who have sickle cell disease and are under the age of five years are at increased risk of life-threatening pneumococcal infection due to absent or non-functional spleens and a decreased immune response. To prevent pneumococcal infection, the American Academy of Pediatrics recommends the use of penicillin prophylaxis in children with SCD under the age of five and in older children who have had a previous severe pneumococcal infection or have functional/surgical asplenia (asplenia is the absence of spleen and/or its functions).
Vaso-Occlusion: Vaso-occlusion relates to, results from, or is caused by the blockage of a blood vessel.
Otoacoustic Emissions (OAEs): Otoacoustic emissions are sounds given off by the inner ear when responding to a sound. There are hair cells in the inner ear that respond to sound by vibrating. The vibration produces a very quiet sound that echoes back into the middle ear. This sound is the OAE that is measured.