A 5-year-old boy is brought to the clinic by his parents due to hearing loss. Over the past year, the patient has had increased difficulty hearing normal conversations. He was born at 36 weeks gestation and was small for gestational age but otherwise has had no medical problems. He is at the 50th-75th percentile for height, weight, and head circumference. A tuning fork held over the middle of the forehead sounds louder in the left ear. Tuning fork sounds are better heard with air conduction bilaterally. Which of the following is the most likely etiology of this patient's hearing loss?
Interpretation of Rinne & Weber tests | ||
Rinne result | Weber result | |
Normal | AC > BC in both ears | Midline |
Conductive | BC > AC in affected ear, | Lateralizes to affected ear |
Sensorineural | AC > BC in both ears | Lateralizes to unaffected ear, |
Mixed | BC > AC in affected ear, | Lateralizes to unaffected ear, |
AC = air conduction; BC = bone conduction. | ||
This patient's Weber test localizes to the left (unaffected) ear, and he hears air conduction louder than bone conduction bilaterally. These findings are consistent with right-sided sensorineural hearing loss (SNHL). SNHL results from damage to the inner ear or auditory nerve. The most common cause of nonhereditary SNHL in children is congenital cytomegalovirus (CMV) infection.
Congenital CMV is transmitted transplacentally from the mother to the fetus in utero. Although some infants are born with features of CMV (eg, small for gestational age, microcephaly, jaundice, hepatosplenomegaly), most infected infants are asymptomatic. Hearing loss occurs in up to 50% of symptomatic and 15% of asymptomatic patients; it may be present at birth and progress, or its onset may be delayed until later in childhood. One or both ears can be affected.
Diagnosis typically involves CMV PCR testing of the urine or saliva. Symptomatic infants are treated with antivirals to prevent progressive hearing loss. Treatment is not recommended for asymptomatic individuals with isolated SNHL.
(Choices A, B, D, and F) Cholesteatoma, chronic otitis media, foreign body, and otosclerosis affect the middle or outer ear and can cause conductive hearing loss. Patients with this type of hearing loss have louder bone conduction than air conduction in the affected ear; a tuning fork placed on the forehead is also louder in the affected ear. In contrast, this patient hears air conduction louder than bone conduction in both ears, and the tuning fork is louder in the unaffected ear.
(Choice E) Constant exposure to loud noises over a prolonged period can damage the cochlea and lead to high-frequency SNHL. Older children and adults may be affected, but SNHL due to noise exposure is rare at age ≤5.
Educational objective:
Congenital cytomegalovirus infection is the most common cause of nonhereditary sensorineural hearing loss in children. The infection is frequently asymptomatic in infants but can cause progressive or delayed-onset, unilateral or bilateral hearing loss later in childhood.