CYTOMEGALOVIRUS.
Various syndromes and congenital conditions affect both the eye and the ear. This can be attributed in part to the development in the embryo of the eye and ear during the same time period, during the first 12 weeks of pregnancy. There are also similarities between the two organs, such as their common origin. As a result there are many diseases and symptom complexes which affect both sense organs and result in dual sensory impairment or deafblindness. It follows that prenatal causes of deafness may be associated with visual impairment whereas with postnatal causes there will be hardly any association.
Prenatal causes of deafblindness include rubella, cytomegalovirus and toxoplasmosis. Congenital rubella syndrome consists of deafness, cataracts, glaucoma, retinopathy and heart defects. Rubella is well known but in countries with effective immunisation programmes the number of newly diagnosed children is very low. A survey of 666 people known to Sense in Britain included only 2 children with congenital rubella syndrome under the age of 5.
However there are many young peple and adults with congenital rubella syndrome and their education, continuing education, quality of life and health issues remains the major concern for many readers of Deafblind Education. A later edition of Deafblind Education will include an article on the possible delayed effects or manifestations of rubella.
Cytomegalovirus or CMV is a potential prenatal cause of deafblindness. In the UK Sense's Head Office database records 7 people deafblind through CMV compared to at least 280 deafblind through rubella.
Cytomegalovirus means 'large cell virus', and is a commonly occurring virus. It belongs to the herpes virus group which includes chicken pox, cold sore and glandular fever viruses. Frequently the infection passes unnoticed or there may be mild flu-like symptoms. Very occasionally it is more serious and lasts longer, such as with glandular fever. Once infection has taken place the virus remains dormant or harmless within the body - usually with no ill effects. The virus can become active again at intervals. CMV is so common that by the age of 30 about half the people in Britain have already caught it and most people are likely to pick it up at some time in their lives. The virus is spread by saliva, urine and other body fluids. CMV is very difficult to avoid; it is usually caught from someone you are close to who shows no signs of being ill.
If a woman catches CMV durng her pregnancy the virus may sometimes be passed on to the foetus. If this happens some babies may be damaged but perhaps only 10% of affected babies will display symptoms and in only half of these children will the disability be serious.
CMV, like the rubella virus, can cross the placenta and affect the developing foetus. It is only the first, or primary infection of a person during pregnancy which can cause problems. It is very rare that reactivation of CMV in pregnancy causes damage to the foetus.
Problems resulting from congenital cytomegalovirus vary but may include
jaundice, bloodspots on the skin, enlargement of the liver or spleen, spasticity
(disordered control of movement), intracranial and other calcifications
(the deposition of calcium within organic tissue), mental retardation and
seizures. In some cases hearing impairment may be the only sign of
the CMV infection while others will have severe sight problems as well.
Estimates suggest that of 600,000 babies born in England and Wales
perhaps 2,000 will have congenital Cytomegalovirus and of these about 200
have problems as a result. Most children with congenital CMV are
healthy and if not tested for the virus at birth would not be suspected
of having it. It is not known why some babies are affected and others
are not.
Pre-natal diagnosis is not possible as at present there is no test available. There is no vaccine.
References
CaF (Contact A Family) Directory of specific Conditions & Rare Syndromes (updated Dec 93)
Tookey P Cytomegalovirus in Talking Sense (Autumn 87).
Admiraal Rare genetic syndromes associated with visual and hearing defects in Deafblind Education (July - Dec 89).
Best & Brown The Population of Learners with Multi-Sensory
Impairment Distance Education Course: Multi Sensory Impairment:
University of Birmingham.