19 February 2016

People with intellectual impairment often have difficulty processing speech, especially in noise, and in locating the source of a sound. A mild hearing loss will make these tasks even more difficult.

Susan Snashall (UK)

Introduction
Middle ear disease and inner ear hearing loss are both more common in those with Down's syndrome than in the general population. In combination with intellectual impairment even a slight hearing loss can have a significant impact upon the acquisition of language. People with intellectual impairment often have difficulty processing speech, especially in noise, and in locating the source of a sound. A mild hearing loss will make these tasks even more difficult. People with Down's syndrome are unlikely to complain of hearing impairment and it is necessary for hearing loss and middle ear disease to be detected by screening procedures if remedial action is not to be delayed.

Anatomy
Orofacial and craniofacial development associated with Down's syndrome contribute to inner, middle and outer ear problems:

  • the adenoids are large
  • the nasopharynx is small
  • swallowing is impaired
  • the Eustachian tube itself is very narrow and more horizontal than usual.

These factors reduce aeration of the middle ear, giving rise to otitis media with infection.

  • the outer ear canal is very narrow making it difficult to visualise the eardrum and for the normal self cleaning mechanisms to operate efficiently.
  • wax is also more copious and more hard than usual, particularly in adults.
  • The outer ear is therefore often blocked by impacted wax.
  • The hair cells of the cochlear may be missing, causing congenital deafness, or simply prone to early degeneration.

Pathology
People with Down's syndrome produce copious mucus, which then becomes infected due to immunodeficiency. Middle ear infections are very common and may proceed to perforation and cholesteatoma. Otitis media with effusion follows Eustachian tube dysfunction and does not tend to resolve spontaneously because of the anatomical characteristics. (In ordinary children 90% will resolve spontaneously within 3 months).

Conductive hearing loss
This results from middle ear infections and from otitis media with effusion (glue ear). It may be mild or moderate in degree, but any degree of hearing loss will affect language development in the presence of intellectual impairment. Adults will have conductive deafness due to impacted wax, perforations or middle ear infections and scarring.

Sensory-neural hearing loss
Children with Down's syndrome are more likely to have congenital permanent inner ear hearing loss than the general population (which has an incidence of 1:1000). From teenage years onwards they a likely to develop degenerative cochlear changes, and most will have a significant hearing loss by the age of 40 years.

Detecting hearing problems:
Children with Down's syndrome should have an annual hearing test using a test suitable to their level of development:

  • Newborns with Down's syndrome - objective test (Otoacoustic emissions or auditory brainstem responses). Those who fail the screen are then seen for further testing and intervention if required. Behavioural observations will substantiate the objective tests at this age
  • Developmental age of 10 months - Visual Reinforcement Audiometry.
  • Developmental age of 2 years - Conditioning play audiometry
  • Adults - Hearing assessment every 5 years using pure tone audiometry if possible, supported by a word test.

Tympanometry, a technique for detecting fluid in the middle ear space, is useful at all ages.

Detecting middle and outer ear disease:
All hearing tests should be accompanied by otoscopy as the ears are so often blocked by wax and serious middle ear pathology will be missed if not sought. Adults should have otoscopy every year to detect wax.

Treating hearing impairment:

  • Wax should be softened on a regular basis with olive oil and removed by syringing as required.
  • Antibiotics may control chronic infection of the nose, nasopharynx and ears.
  • Grommets/T tubes/Tympanostomy tubes, which are small tubes placed in the ear drum to maintain air in the middle ear are used if the external canal is large enough to give a surgical view of the ear drum. They extrude spontaneously and may need to be reinserted, as the otitis media is likely to recur.
  • Surgical repair of perforations and removal of cholesteatoma may be required
  • Inner ear hearing loss can only be helped with amplification using some form of hearing aid.

Hearing aids and Down's syndrome:
As hearing loss is likely to have such an impact upon language development in Down's children, and upon cognition in Down's adults suffering from early dementia, amplification is considered even for mild hearing losses and for conductive hearing loss which is likely to be present for more than a few months. The hearing loss is almost always accompanied by recruitment, which can cause sound intolerance. The hearing aid prescription will be such as to avoid tolerance problems in noisy places such as special schools and day centres. As the ears are small miniature ear level instruments will be required. Hearing aids may only be worn for limited periods, and if so this should be at times of language training. All children will have the assistance of an Advisory Teacher for the Hearing Impaired, and all adults the help of a Specialist Speech and language Therapist.

Even with motivated carers personal hearing aids may not be tolerated. For children a classroom FM system is an alternative as these systems improve the detection of speech in classroom noise. For adults the best solution may be a change in the communication strategy used with the person.

This article first appeared on the site in 2002.