When a clinical trial of any drug or therapy has been completed, it is important that the results are published in a medical journal, so that other health professionals are made aware of them. In this way, doctors can obtain solid clinical evidence about the treatment options available (and the situations in which they are likely/unlikely to be worth pursuing), helping them to manage their patients in the best, most time-efficient, manner.

A ketogenic diet that is high in fat and low in protein and carbohydrate has been used to treat seizures in children for almost a century; but until recently the clinical evidence supporting it had several limitations. In May 2008, however, the results of the first ketogenic randomised controlled trial (RCT; considered to be the most reliable trial design) were published in the journal Lancet Neurology. These showed that, for children with refractory epilepsy (epilepsy that has not responded to at least two anti-epileptic drugs (AEDs)); following the diet in addition to AED treatment can significantly improve seizure control (compared to AED treatment alone). This raised the diet's profile as a viable treatment option and gave doctors more confidence when prescribing it.

The benefits of the ketogenic diet, and an adapted version of it known as the modified Atkins diet, are currently well reported for symptomatic generalised epilepsies (generalised epilepsies with known causes), for example Lennox-Gastaut syndrome; but their specific effects in idiopathic generalised epilepsies (generalised epilepsies of unknown cause), such as childhood absence epilepsy (CAE), have never been published. CAE is one of the most common childhood epilepsies, and this lack of evidence could mean that significant numbers of children with epilepsy are missing out an effective treatment option.

In a recent study, researchers at the John Hopkins Hospital (JHH) in Baltimore, US, tried to address this issue. They used both existing publications and evaluation of children treated at JHH, to analyse the efficacy of the ketogenic and modified Atkins diets in CAE and juvenile absence epilepsy (JAE). CAE and JAE are similar conditions, but the age of onset in JAE is usually slightly later (9-13 years compared to 4-9 years).

The scientists reviewed the results of 17 published studies in which children with refractory epilepsy, including sub-groups with absence epilepsy, were prescribed the ketogenic diet. The studies reported clear outcomes for 133 children who had followed the diet, and showed that approximately 69% of these children had achieved a greater than 50% reduction in seizures. Of this 69%, approximately 34% had become completely seizure free.

These findings are encouraging, but they relate to a range of epilepsies, not just CAE and JAE. The scientists therefore looked at the effects of the ketogenic and modified Atkins diets in 21 children being treated specifically for refractory absence epilepsy at JHH, to see how the results compared. Eight of the children were prescribed the ketogenic diet and 13 the modified Atkins diet.

Within the group the average age of seizure onset was 4.5 years and the average age at the start of diet treatment was six years. Prior to starting their respective diets, the average number of AEDs the children had tried was four, and when the diets began, the average number of AEDs being prescribed to each child was one. Seizure outcomes were evaluated at three months post diet onset.

After three months on their respective diets, 18 (82%) of the children had achieved more than a 50% reduction in seizure frequency. Of these, 10 (48% overall) had achieved more than a 90% seizure reduction and four (19% overall) were seizure free. Variables such as the child's age at diet onset, number of AEDs used previously, diet used and gender did not appear to have an influence over seizure outcome, although the researchers acknowledge that larger studies might show otherwise.

Compared to the published data, these results show a slightly higher rate of 'greater than 50% seizure reduction' - 82% vs 69%, but a small reduction in seizure freedom rates - 19% vs 34%. These differences are not conclusive, however (larger studies specifically into absence epilepsy need to be performed) and overall the findings were seen as comparable.

Although larger studies are required, this is the first documented evidence that the ketogenic and modified Atkins diets are effective in the treatment refractory absence epilepsy (and potentially as effective as in the treatment of other forms of childhood epilepsy). This will hopefully encourage neurologists to consider the diet in cases where they might not normally have done, and could allow some children with refractory absence epilepsy the chance for better seizure control, sooner.

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