דיאטה קטוגנית - מתוך מאמר - המשך
Who is helped by the diet? Most patients in our population are 5–10 years of age with long-standing, intractable Lennox-Gastaut Syndrome or another mixed epilepsy syndrome. The ketogenic diet is effective independent of factors such as age, seizure type, and EEG pattern. Patients with gastrostomy tubes may be the most ideal candidates. In addition, the diet can be used for patients who are not refractory to other treatments, although the time and commitment can be considerable when compared with drug therapy. The ketogenic diet's value for patients not in the typical age range (5–10 years old) has recently been shown. Both infants and adolescents can do well and maintain the diet for long periods. here are several disease states in which the ketogenic diet is not only beneficial, but may be life saving. The two main disorders are glucose transporter protein deficiency (GLUT-1) and pyruvate dehydrogenase deficiency. Other disorders—such as pyruvate-carboxylase deficiency, defects of fatty-acid oxidation, carnitine deficiency, and possibly some of the mitochondrial disorders—are thought to be contraindications to the ketogenic diet.9 One disorder that requires more investigation is infantile spasms. infants who had mostly not responded to drugs such as corticotropin and vigabatrin were treated with the ketogenic diet.30 About half had greater than 90% improvement over 3–12 months, including 88% of those who did not respond to corticotropin. Independent predictors of favourable outcomes included age less than 1 year and exposure to three or fewer anticonvulsants. Theoretically, the ketogenic diet would be even more beneficial as first-line therapy, and might avoid the sideeffects of corticotropin, vigabatrin, and other anticonvulsants. A multicentre trial of the diet as initial therapy for infantile spasms is being planned. Long-term outcomes Children on the ketogenic diet at our institution are followed up regularly in the clinic with laboratory studies (lipid profile, electrolytes, anticonvulsant levels, and urine concentrations of calcium and creatinine) every 6 months. Parents are advised to check weights and urine ketones at least twice a week and to maintain frequent email or telephone consultation with our group. At this time we do not recommend routine testing of serum beta hydroxybutyrate, but one study indicated it is a more accurate guide to seizure control.34 Drugs for these patients should only be managed by the centre implementing the diet. The diet's efficacy has been assessed in several studies. The largest series of 150 children showed that after 1 year on the diet 50% had a >50% seizure reduction, and 27% specifically had >90% improvement.26 When followed up for an additional 3–6 years, the benefits lasted even after the diet was discontinued; with 44% having >50% improvement.35 Compared with results of most anticonvulsant drugs, which provide a 30–40% chance of >50% improvement in add-on trials, the diet's efficacy is apparent. Because many patients placed on the ketogenic diet have not responded to more than three anticonvulsants, the efficacy is even more significant. A double-blind, placebo-controlled trial (glucose versus saccharin solution given during the initial fasting period) of the diet for Lennox-Gastaut syndrome with multiple seizure types has been completed and is being analysed. This study will be one of the few to formally study the effects of the ketogenic diet prospectively. The ketogenic diet may have other benefits. The money saved through the use of fewer drugs and revised care can be significant.38 and 39 Behaviour has also been reported to be improved in children with epilepsy both with and without autism. Side-effects There are common, uncommon, and rare side-effects of the ketogenic diet. Common side-effects include lack of weight gain (often planned), acidosis (worse with illness), and constipation. Less common are kidney stones (6%), growth inhibition (more significant at young ages), and hyperlipidaemia. The risk of kidney stones does not seem to be increased by the additional use of acetazolamide, topiramate, or zonisamide—anticonvulsants that independently increase the risk of kidney stones by 2–4%. Children had an increase in their cholesterol, triglyceride, and low-density lipoprotein concentrations from the 75th to the 99th percentiles after 3 months. The increase in cholesterol may be caused by ketogenic-diet induced decrease in apolipoprotein B, the major serum carrier of cholesterol. The changes tended to plateau after 6 months and normalised when the diet was stopped. Adjustments to the diet (eg, increased protein and polyunsaturated fats) can be made in children with significantly high lipid concentrations. The long-term results of these side-effects have not been adequately studied, but few children at our centre have had to discontinue the diet because of them. Rare (case reports only) side-effects include cardiomyopathy, prolonged QT syndrome, vitamin and mineral deficiencies, pancreatitis, basal ganglia injury, and bruising. We have not seen these complications in our 500 patients and do not routinely screen for them. A recent study in rats that were given the diet for 1 month introduced concerns about cognition and brain growth, although these concerns have not been raised by any study of human beings. Discontinuation of the diet Children are kept on the ketogenic diet for as long as it is beneficial, but typically 1–2 years if it is successful. Half of the patients at our centre are on the diet for 1 year, but discontinue earlier if it is deemed ineffective or too restrictive. Similarly to anticonvulsants, the diet is tapered over several months by lowering the fat to protein and carbohydrate ratio, then slowly relaxing restrictions on weighing foods and measuring carbohydrate intake. The replacement of high-fat cream with whole milk and eventually with skimmed milk can be used to discontinue the diet more rapidly. When families feel the diet is not effective any longer, it can be tapered slowly while seizures are monitored.