What Causes Hearing Loss?

Patient Presentation
A 12-year-old male was referred after his school auditory screening test which was abnormal. This was repeated and was abnormal again.
He was referred by the school to his local physician. The physician found in the patient’s history a possible decrease in hearing for the past several months but the patient had never complained. He is a regular user of head phones and his parents complain that he does play music loudly.
The past medical history is normal and he takes no medications.
The review of systems showed no vertigo, tinnitis, nausea, weakness, pain or headaches. He has been active with no problems with coordination or gait. He has been acting normally according to his parents, friends and teachers.
The family history is negative for skin lesions, benign or malignant tumors, seizure disorders, hearing loss, vertigo, tinnitis, genetic syndromes or renal abnormalities.

The pertinent physical exam showed a well-developed male with average growth parameters. The skin examination was normal and the HEENT evaluation was normal. The neurological examination was normal including cranial nerves and gait.
An auditory brain response confirmed the unilateral hearing loss.
The radiologic evaluation showed a localized mass in the left internal auditory canal that appeared benign in nature.
He underwent resection with a left middle fossa craniotomy and the pathology showed a diagnosis of a benign acoustic neuroma. A genetic evaluation revealed no increased risk of neurofibromatosis type II.
The clinical course showed him to be doing well post-operatively with some left facial nerve palsy that was improving over time.

Figure 35 – Axial unehanced images from a CT scan of the left and right temporal bones. The left internal auditory canal (on the right image) is smoothly expanded and much larger than the right internal auditory canal (on the left image). This enlargement of the left internal auditory canal corresponds to the location of an enhancing mass within it noted on an MRI of the brain performed with contrast from an outside institution.

Acoustic neuroma are extra-axial intracranial tumors arising from Schwann cells either in the cochlear (~5%) or vestibular nerve (~95%). They usually are benign but can cause problems because they occupy space especially in the cerebellopontine angle.
Acoustic neuromas occur in 0.7-1.0/100,000 population. They are commonly associated with Neurofibromatosis type II because of a defective tumor suppressor gene on chromosome 22. Bilateral acoustic neuromas are a principle feature of neurofibromatosis type II but other tumors also occur.
Unilateral hearing loss is the most common symptom that causes acoutic neuroma presentation. Tinnitus and headaches also may occur but it is uncommon for there to be vertigo or facial weakness. Facial numbness occurs in about 25% of patients. Treatment is usually surgical
Complications may include arterial injury, facial paralysis, cerebral spinal fluid problems and cerebellar injuries. Recurrence risk is 5-10% or lower, and most patients have good facial nerve function. Hearing may or may not be preserved. Some studies have shown stable hearing over time and others have shown some deterioration.

Hearing screening is recommended for all newborns in the United States by the American Academy of Pediatrics. Any parent concerned of hearing loss at any age should be taken seriously. At least one study has shown that parents identify their child’s hearing loss as much as 12 months earlier than physicians.
Subjective hearing screening is recommended at each health maintenance visit after birth until 3 years and again at the 11, 13, 14,16, and17 year visits. Objective measurements are recommended at the yearly health maintenance visits from 4-10 years and again at the 12, 15, and 18 year visits.

Learning Point
Hearing problems can range from fairly minor to deafness. The causes vary based on age, type of loss (sensoryneuronal or conductive), degree and audiometric configuration.
Sensorineuronal hearing loss involves the cochlea and neural connections to the brain and auditory cortex.
Conductive hearing loss involves structures from the external ear to the oval window.

Deafness is defined as a hearing loss > 90 dB. The person will not be able to distinguish between different speech elements. Hearing aids are often recommended for losses > 25 dB. They may also be useful for certain patients with less loss.
Special classroom help is often recommended at > 55 dB loss. Cochlear implants are considered at 70 dB of loss.

As a comparison, water dripping is 0 dB of sound and this is normal hearing. A clock ticking is 20 dB of sound, and a person with this loss may miss some speech consonants. A whisper is 30 dB of sound and a person with a loss may hear only louder noises or have mild speech problems.
Conversational speech is 40 dB and a person with a lossmay hear speech only as a whisper. A baby crying is 55 dB and a person may only be able to hear loud speech at a few feet with this degree of loss.
Other common environmental sounds are telephone ringing (90 dB), lawn mower (100 dB) and an airplane (110 dB).

Causes of sensineuronal loss include:

  • Genetic
    • Deafness – not otherwise clinically differentiated
    • Alport syndrome
    • Jervell and Lange-Nielsen syndrome
    • Hunter syndrome
    • Pendred syndrome
    • Usher syndrome
    • Wardenberg syndrome
    • Many others
  • Acquired
    • Congenital infections – e.g. cytomegalovirus, rubella, syphilis, toxoplasmosis
    • Maternal diabetes
    • Infections – i.e.meningitis, measles, mumps, viral cochleitis
    • Medication toxicity – e.g. gentamicin, vancomycin, etc.
    • Ototoxicity – e.g. hyperbilirubinemia
    • Acoustic trauma
    • Tumor – i.e. acoustic neuroma, meningioma, etc.
    • Meniere’s disease
  • Malformation
    • Klippell-Feil syndrome

Causes of conductive hearing loss include:

  • Genetic
    • Cryptophthalmos syndrome
    • Paget disease
    • Otopalatodigital syndrome
    • Treacher Collins syndrome
  • Acquired
    • Cerumen occlusion
    • Cholesteatoma
    • Otitis media – i.e. acute and chronic
    • Ossicular dislocation
    • Tympanic membrane disruption
    • Trauma – e.g. head trauma, otic trauma, scuba diving, high altitude trip
  • Malformation
    • Goldenhar syndrome
    • Hemifacial microsomia

Questions for Further Discussion
1. What point do auditory brainstem responses play in the evaluation of hearing loss?
2. What are indications for a genetics evaluation in a patient with hearing loss?
3. How would the differential diagnosis change if the patient also has tinnitus or vertigo?
4. What hearing screening tests can be used at different ages?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Information prescriptions for patients can be found at MEDLINEplus for this topic: Acoustic Neuroma

To view current news articles on this topic check Google News.

Illingworth RS. Common Symptoms of Disease in Children. Blackwell Scientific Publications: Oxford. 1988:199-203.

American Academy of Pediatrics Policy Statement.
Recommendations for Preventive Pediatric Health Care. Pediatrics. 2000;105:645-646. Available from the Internet at: http://aappolicy.aappublications.org/cgi/reprint/pediatrics;105/3/645.pdf ( cited 2/2/06).

American Academy of Pediatrics Policy Statement. Hearing Assessment in Infants and Children: Recommendations Beyond
Neonatal Screening. Pediatrics, 2003;111:436-440. Available from the Internet at: http://aappolicy.aappublications.org/cgi/reprint/pediatrics;111/2/436.pdf (cited 2/2/06).

Roland PS. Skull Base, Acoustic Neuroma: Vestibular Schwannoma. eMedicine.
Available from the Internet at http://www.emedicine.com/ent/topic239.htm (rev. 6/15/2003, cited 2/2/06).

Rudolph CD, et.al. Rudolph’s Pediatrics. 21st edit. McGraw-Hill, New York, NY. 2003:485-489.

ACGME Competencies Highlighted by Case

  • Patient Care
    2. Essential and accurate information about the patients is gathered.
    3. Informed decisions about diagnostic and therapeutic interventions based on patient information and preferences, up-to-date scientific evidence, and clinical judgment is made.
    4. Patient management plans are developed and carried out.
    7. All medical and invasive procedures considered essential for the area of practice are competency performed.
    8. Health care services aimed at preventing health problems or maintaining health are provided.
    9. Patient-focused care is provided by working with health care professionals, including those from other disciplines.

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Practice Based Learning and Improvement
    13. Information about other populations of patients, especially the larger population from which this patient is drawn, is obtained and used.

  • Interpersonal and Communication Skills
    19. The health professional works effectively with others as a member or leader of a health care team or other professional group.

    Donna M. D’Alessandro, MD
    Associate Professor of Pediatrics, Children’s Hospital of Iowa

    March 27, 2006