Otitis media (OM) - inflammation of the middle ear - is a common childhood affliction the world over. Every year, there are about 1.5 million cases in the UK, and 2.2 million cases in the US. It is caused by a bacterial or viral infection spreading to the ear from the nose, throat or sinuses; symptoms include ear pain, redness and swelling, with bulging of the eardrum. There may also be a discharge (effusion) in the later stages when the accumulation of pus causes the eardrum to burst.

Unchecked, OM can become a chronic condition; when the discharge is sticky and persistent, it is known as ‘glue ear’. If the condition doesn’t clear up, the build-up of fluid can cause hearing loss by blocking the tubes to the ears and by preventing the vibration of the bones that conduct sound in the middle ear. Over time, this can affect the child’s speech and behavioural development. The thick catarrh can also act as a breeding ground for bacteria and fungi, making the child prone to reinfection.

Inserting grommets restores hearing by allowing air back into the middle ear. It also relieves the symptoms by equalising the pressure between the middle ear and the outside. However, many doctors use surgery - ‘myringotomy’ - alone to manage OM, a function for which it repeatedly fails. Four years after a 1992 UK government leaflet alerting doctors to the ineffectiveness of the procedure was published, an estimated 90,000 grommet insertions were avoided (BMJ, 2001; 323: 1096-7).

Antibiotics were the first port of call for many doctors in the past, but are prescribed less frequently as more resistant strains of bacteria emerge. Disturbingly, however, the US seems to be advocating a heavier reliance on grommet surgery as antibiotics become less effective. One study suggests surgery for OM, along with adenoidectomy, in preference to repeated treatments with antibiotics - partly because surgery may be cheaper than a prolonged course of medication (Pediatr Infect Dis J, 1998; 17: 1090-8).

How is the operation performed?
The child is put under general anaesthetic and the grommet (a tiny plastic tube) is placed into a small nick made in the eardrum. The operation takes about 10-15 minutes and the child is allowed to go home after an hour or so. The tubes stay in place for 6-15 months, depending on the type of tube and the child.

Is the operation safe?
Grommet insertion is a relatively safe procedure, involving the usual complications of general anaesthesia and a small risk of permanent hearing loss (0.7 per cent). Other complications are:

* risk of eardrum perforation (about 2-3 per cent)

* 4.8 per cent risk of damage to the eardrum (Acta Otorrinolaringol Esp, 1996; 47: 349-53)

* displacement of the grommet into the middle ear (J Laryngol Otol, 2000; 114: 448-9)

* persistent scars or damage to the eardrum, or a cholesteatoma (benign tumour), which occur more frequently in grommet-treated ears (HNO, 1987; 35: 55-60)

* tympanosclerosis (loss of hearing through scarring of the eardrum), which can affect up to 48 per cent of intubated ears (J Laryngol Otol, 1983; 97: 489-96).

What doctors don’t tell you

* The purpose of grommets is to drain the middle ear, allowing air to enter, thus equalising the pressure between the middle ear and the outside; reduce pain; and restore hearing. Grommets do not control bacterial/viral infection - apart from helping to disperse sticky catarrh that might otherwise cause reinfection - and are only effective for as long as they remain in the ear (Am J Otol, 1985; 6: 455-60).

* Grommets do not prevent OM recurrences (HNO, 1987; 35: 61-6).

* The younger the child when grommets are first used, the more likely the need for repeat surgery (Clin Otolaryngol, 1987; 12: 371-5).

* Middle ear fluid can occur with no infection present. The eustachian tubes in an infant are angled differently, so fluid may tend to collect in the ear. Given time - and no intervention - the ear will develop normally and clear the fluid by itself.

* Around 80 per cent of cases of glue ear heal spontaneously within a year, if left alone (HNO, 1987; 35: 55-60).

* Hearing loss for six months or less will have little effect on the development of language skills. A study of more than 6000 children found 'no significant correlations' between middle ear effusion (MEE), and scores for various measures of spontaneous expressive language, speech-sound production and other measures of mental function.

The most dramatic influence was found to be the socioeconomic background of the child. Scores were consistently higher among those children from the more advantaged backgrounds and lower among those from disadvantaged families.

The researchers concluded that MEE may have some effect, but this is more likely to be compounded by 'as yet unidentified' factors that predispose a child to both OM and certain types of impaired behaviour (Pediatrics, 2000; 105: 1119-30).

* Persistent glue ear may be caused by allergies, which can affect mucociliary function in the eustachian tube, causing obstruction leading to underventilation of the middle ear and the effusion of fluid (Curr Allergy Asthma Rep, 2002; 2: 309-15).

Other studies have also found a significant link between food allergy and serious recurrent ear infections. In one investigation involving 104 children suffering from OM, food allergies were found to be a factor in 78 per cent of them. When these allergic children were put on food-elimination diets, their condition improved significantly in 86 per cent of cases. On reintroducing the suspected offending foods back into the diets of the children who had shown improvement, a recurrence of the condition was provoked in 94 per cent (Ann Allergy, 1994; 73: 215-9).

* Infected, but ‘dry’ ears, are unlikely to need grommets. If a child suffers from a bout of OM, but the ears remain dry, there is only a 5.5 per cent chance that grommet insertion will later be necessary (J Laryngol Otol, 1980; 94: 1117-24).

Michelle Clare