How the ear works

The ear is divided into three parts, an outer ear, a middle ear and an inner ear. Sound enters the outer ear through the ear canal and hits the ear drum, then vibrates through the three small bones (ossicles) in the middle ear and into the inner ear, from which messages are sent to the brain.

Transmission of the vibrations through the outer and middle ear is purely mechanical. If anything goes wrong with this part of the process the hearing problem is called conductive deafness. Conversion of the mechanical vibration signal to a nerve message in the inner ear, its transmission from there to the brain and its decoding within the brain depends on nerves and brain tissue functioning normally. If anything goes wrong in this part of the transmission process it is called sensorineural deafness.

Glue ear is a form of conductive deafness caused when a sticky fluid fills the middle ear space. This space normally contains a film of clear fluid and air. The glue prevents the ossicles from vibrating freely and so transmission of the sound vibrations to the inner ear is faulty. The effect on hearing is much the same as filling a musical drum with water – sound is muffled.

Glue ear can cause deafness, infection, pain, delayed speech development, temporary behaviour problems and poor school progress. If left untreated any of these conditions are likely to persist, possibly affecting long-term speech, language and educational development.
The more able children will be more adept in compensating for hearing loss; the less able they are, the less they can compensate. Thus, it is even more important to treat glue ear in a child with Down’s syndrome than in an ordinary child.

If a child develops glue ear one of four things may be done:

• WAIT FOR IT TO GET BETTER ON ITS OWN

In ordinary children glue ear is a self-limiting problem and children tend to grow out of it as the Eustachian tube and other cavities become larger. It is rare to find glue ear persisting beyond age 7. It can come and go in early childhood and often fluctuates during the year, being much better or non-existent in the summer months.

In children with Down’s syndrome however, the condition tends to be much more persistent and the glue formed seems stickier than in ordinary children.

• ANTIBIOTICS AND DECONGESTANT MEDICINES

If the glue ear seems to be triggered by an acute infection or by recurrent upper respiratory infections a doctor may give a course of low-dose antibiotics for about 6 weeks. This may be combined with decongestant medicine to dry up secretions. For some children this clears up the problem so that no further treatment is necessary. Some may benefit in the short term but need a further course the next time they get an infection. For those awaiting grommet operations this treatment sometimes proves a useful interim measure to keep things at bay and improve hearing until the operation can be done. Decongestants given as nose drops are not recommended and can lead to overproduction of mucus once the immediate effect wears off.

• INSERTION OF GROMMETS

If glue ear does not clear up spontaneously in a few months or respond to antibiotics, a small operation can be carried out to remove the cause of the obstruction and clear fluid from the middle ear. Under a general anaesthetic the ear drum is punctured with a very fine instrument. The fluid is then sucked out and a grommet may be inserted into the opening in the ear drum. Sometimes removal of the adenoids is also indicated.

A grommet looks like a small plastic dumb-bell with a hole through the middle to ventilate the middle ear. Sometimes larger drainage tubes called T-tubes are used.

These operations can occasionally be difficult or impossible in young children with Down’s syndrome because the ear canal may be so narrow that the surgeon cannot operate. In this situation hearing aids may be helpful, not only to improve hearing but because wearing an aid tends to widen the ear canal so that an operation might be easier at a later age.

The grommet remains in the ear drum to help ventilate the middle ear. However the healing tendency of the ear drum pushes the grommet out in anything from 6-8 months, on average, and the hole then heals by itself. The grommet may easily be removed from the ear canal, in the outpatients’ department, or it may fall out unnoticed, in a lump of wax. There is no need to look for the grommet, or consult your GP, unless you have problems. Your local ENT surgeon will usually check the grommet around 3-6 months after the operation, and will check the hearing at that time and after the grommet has fallen or been taken out.

In ordinary children glue recurs in about 20% of patients and further grommets may be necessary. In children with Down’s syndrome however, not only is recurrence much more likely, but because the glue is so thick, the grommet itself often becomes blocked within a month or two of operation and the improvement in hearing may be short-lived. Because of this often disappointing outcome some ENT surgeons, hearing therapists and audiometrists now recommend hearing aids as the preferred treatment for children with glue ear who also have Down’s syndrome. Grommets do work for some of these but the failure rate is high. It is not good practice to carry out repeated operations because every time a grommet is inserted the ear drum has to be punctured and every time one falls out it leaves a tiny scar.

• HEARING AIDS

Hearing aids merely amplify (make louder) the signal which is sent through the middle ear. They can be fitted as early as the first year of life.
All children with Down’s syndrome should have their hearing tested at birth and at least every year until age 5 and thereafter every 2 years whether or not parents feel there may be any problems. If you are worried, ask for a specialist hearing assessment by a community audiologist or by a specialist hospital based audiology and ENT team.

Hearing aids may be helpful in children with glue ear who continue to have moderate to severe hearing loss, despite the insertion of grommets. It is very important that these are properly fitted, and that hearing is regularly checked both with and without the aids.