ONE OF the hardest decisions that Lucy and Joe Blenkinsopp ever had to make centred on their son, Sam. He was less than a year old, but their decision could determine how he would look for the rest of his life.

Sam was born with an asymmetrical skull which appeared slightly bulbous on the left, and flattened at the back. Doctors could not say with any certainty if it would stay the same or get worse as he got older and, as his brain grew, distort his skull further and twist his features. The remedy was radical surgery in which their baby would be cut from ear to ear, his scalp peeled down, and part of his skull removed by a neurosurgeon, exposing the brain. The skull bones would then be 'remodelled' by a craniofacial surgeon and replaced. It was an alarming prospect, but the younger the child the easier and less traumatic the operation.

Sam Blenkinsopp suffered from a relatively rare condition known as cranio-synostosis, in which skull bones fuse prematurely. Until last week few people had heard of it, but then doctors from North Yorkshire Health Authority reported a highly unusual cluster of 22 babies with cranio-synostosis in a small area between Selby and York. A fifth of the cases are genetic in origin, but as yet there is no explanation for the others. Environmental factors such as lead, pesticides or other chemicals have been suggested.

It is not known how many children are born with cranio-synostosis each year, but estimates range from between one in 2,000 and one in 4,000, with about 100 new cases a year.

Babies with oddly shaped heads are not that unusual, and GPs and health visitors are frequently called upon to reassure anxious parents. A baby's skull is malleable and subject to many influences: how the foetus lay in the womb, and how it was delivered - by forceps or ventouse (vacuum) extraction for example. 'Even postural influences such as sleeping positions may cause distortions of the skull,' according to Norman Waterhouse, a craniofacial surgeon and head of the craniofacial unit at Charing Cross Hospital, London. 'In the majority of cases the head will resume a normal shape as the child gets older.'

But occasionally there is a problem; cranio-synostosis is a generic term used to describe a condition in which one or more of the 'expansion' joints in the skull, known as sutures, fuse prematurely. A baby has six pliable plates of bone making up the skull that 'float' on the surface of the brain, allowing it to grow and expand.

If a suture fuses early, the brain cannot not grow normally, and pushes out another part of the skull, causing an abnormal appearance and sometimes distortions of the eyes and face. Occasionally, cranio-synostosis is only one symptom of very rare syndromes, such as Apert's and Crouzon's syndromes, and these babies tend to be more severely affected, and suffer a range of other physical deformities.

The degree of skull abnormality in cranio-synostosis depends on which sutures are fused and how many. Heads can appear bow or keel-shaped, very long, or triangular. In most cases the affected children have normal intelligence, and the problem is cosmetic. However, if more than one suture is fused, and the brain's growth is restricted in more than one area, there is a risk of mental retardation and surgery becomes a necessity.

In many respects it is easier for the parents of these children to face up to the trauma of surgery than the parents of less severely affected children such as Sam Blenkinsopp, according to Daniela Hearst, principal clinical psychologist in the craniofacial unit at Great Ormond Street Hospital, London. Do parents say no to surgery and have their son or daughter at 16 blaming them for a life marred by some deformity? Do they wait until the child is older, when she or he has been teased because of their odd appearance, and when surgery will be more difficult? Or do they say yes to major surgery in a young baby? 'The easier option is when the surgery is medically dictated,' Ms Hearst said.

In Sam Blenkinsopp's case one of the sutures in his skull was partially fused, but X-rays and CAT scans failed to establish to what degree - which is why doctors were uncertain about his prognosis. Initially, the Blenkinsopps, who live in Southfields, in south-west London, were at odds with each other over what should be done. Mrs Blenkinsopp believed that if there was the slightest chance that their son would look 'strange', or different from other people in later life, then he should have the operation.

'I am of the opinion that this world is hard enough without your appearance making it even harder. But my husband found it incredibly difficult to come to terms with. He felt there was so much that could go wrong,' she said. 'We discussed it endlessly, but I didn't want to influence him. He had to work it out himself.'

It was two weeks before Joe Blenkinsopp came to the same conclusion as his wife, and Mr Waterhouse operated on Sam, then aged 13 months, last October. When he returned from theatre he looked 'quite horrendous', his mother said. 'His whole head was very swollen, his eyes were swollen and bruised and he was black and blue. Bella, my daughter, who was two, burst into tears when she saw him.' But within a day or two Sam was driving in a toy car up and down the hospital corridor, and the swelling started to subside. In fact, he took his first steps on the day that he was discharged, less than a week after his operation. There have been no psychological or developmental problems; all that remains is a scar on his scalp, running from ear to ear He will, however, continue to see Mr Waterhouse until he is a teenager.

Sam Blenkinsopp was lucky on two counts; when his skull was opened up the degree of fusion was much greater than suspected and would have distorted his face, causing the 'drifting' of one eye as he got older. But he was also lucky because his condition had been properly diagnosed in the first place. It was a chance remark by a consultant who was treating Sam for a chest infection when he was three months old that alerted the Blenkinsopps to the problem. Initially, his skull deformity was blamed on a twisted muscle in his neck and he was given physiotherapy.

Mr Waterhouse believes that many children with more severe problems are being missed. They receive inappropriate or no treatment because many GPs and some paediatricians are not fully informed about what cranio- synostosis is, and what craniofacial surgery can offer. Following publicity about the Yorkshire cases last week, the Independent was contacted by several parents who were concerned about the shape of their children's skulls and were not happy with advice they had received. One couple from west London had seen a GP, an orthopaedic surgeon, a physiotherapist, and a cranial-osteopath. No one had suggested assessment by a craniofacial or neurosurgeon.

Any parent who is concerned, should seek referral to one of the specialist centres in Oxford, Birmingham or London. The optimal age for treatment is between three and six months; after this it becomes more complicated but is still worthwhile, Mr Waterhouse said. 'We can, more or less, make every child we see look better - or more as nature intended.'

(Photograph omitted)