In DS, seizures typically occur during the first year of life in otherwise healthy infants and are often triggered by fever. Seizures are initially unilateral or generalized tonic-clonic type, but subsequently become of longer duration, more frequent, and resistant to most antiepileptic drugs (AEDs). Myoclonic seizures (i.e., seizures characterized by myoclonus [i.e., brief, rapid jerks caused by muscle contractions], with immediate recovery and often without loss of consciousness) that are either focal (i.e., involving a localized area of the brain) or generalized (i.e., involving both cerebral hemispheres) begin in most patients with DS after 1 year of age. Modest hyperthermia (e.g., resulting from physical exertion or a hot bath), photosensitivity, respiratory virus, and vaccinations administered at 6 months of age may trigger seizure in infants with DS.
Seizures may last for up to 5 minutes or progress to status epilepticus (SE) and last up to 30 minutes. SE may be frequent initially, but usually decreases with time.
Results of the initial electroencephalogram (EEG) are normal, but changes begin to appear in the 2nd or 3rd year of life. Neurologic, cognitive, and motor development are initially normal in children with DS.
However, developmental regression occurs by age 2 years and progresses, resulting in significant psychomotor retardation. Children with DS have poor language and motor skills and have difficulty relating to others. The mortality rate is 20% by 20 years of age because patients with DS are at increased risk for accidents, infection, and sudden unexpected death. Seizures continue into adulthood, and mortality increases from epilepsy-related causes as persons with DS age.
The goal of treatment is to reduce seizure frequency and prevent the occurrence of SE. However, seizures in patients with DS are difficult to prevent because AEDs are often ineffective and certain AEDs (e.g., phenytoin, vigabatrin, rufinamide, tiagabine, lamotrigine, carbamazepine) can exacerbate seizures. A multi-drug regimen is usually prescribed, and valproate and topiramate are considered first-line treatment for DS.
Other AEDs, including phenobarbital, benzodiazepines (e.g., diazepam), bromides (e.g., potassium bromide), and felbamate as well as the combination of stiripentol (see Food for Thought below), valproate, and clobazam, have demonstrated efficacy in controlling seizures in some patients with DS.
Other therapeutic options include corticosteroids (e.g., prednisone), adrenocorticotropic hormone (ACTH), intravenous immunoglobulin therapy (IVIG), consuming a ketogenic diet (i.e., a high-fat, low-carbohydrate diet that increases ketones in the blood), and vagus nerve stimulation (VNS; i.e., implanting a small device in the upper chest to stimulate the vagus nerve through a series of small electric shocks).
Providing education and emotional support is important for the patient and the parents to assist with strategies for coping with a chronic, life-threatening condition. Early assessment and treatment for developmental delays, behavioral problems, and attention issues is important.
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