The child will usually start having some changes in behaviour and problems with learning or school work, and may have been seen by a psychologist or psychiatrist. The child develops involuntary movements which make him/her stagger or fall backwards, as if pulled by an invisible string. Deterioration in the thought processes continues and myoclonic jerks  start affecting  different parts of the body, coming on like a sudden shock and fading over a few seconds; these particular spasms are very typical and are experienced by all sufferers of SSPE; epileptic seizures may or may not occur. As the condition progresses the child/ young person becomes totally dependent on others for  all their care ; eventually he/ she will fall into a coma. The rate of  deterioration can vary very considerably and it is not usually possible to predict how long the course of the illness may be.

Eventually,  however,  the combination of the diseased brain and physical weakness  becomes too great to sustain life. In some people the course of the illness can be very rapid, leading to death within 9 months of the onset of the symptoms whilst in others the course of the disease can be much slower, with periods of stability, over 10 – 15 years. The condition is not a painful one and the child/young person will mercifully be unaware of what is happening in the later stages of the disease. It is, however, cruelly distressing and frustrating for the child whilst he/ she is aware of the deterioration in abilities, and for the family and friends throughout the illness. Parents and carers will be aware of the child’s increasing frailty whilst he/ she is comatose, and death is relatively peaceful and expected when the time comes.