In most cases children with Dravet syndrome develop normally prior to the onset of seizures. Normal development may continue in the short term after seizures begin. Psychomotor delay, and often regression, usually becomes apparent during the second year (age 1) and is increasingly obvious during the third year (age 2). Ultimately a strong majority of children with Dravet syndrome will have significant and persistent moderate to severe delays and will require care throughout their lives.
The nature and severity of developmental delays can be highly variable from child to child. Well-controlled studies, including periodic standardized developmental assessment of children with Dravet syndrome are needed. The information available about development in Dravet syndrome is largely observational or anecdotal.
Motor Development Though some children with Dravet syndrome experience delays in meeting early motor milestones and learning to walk, most have normal early motor development. With the increase in frequency and severity of seizures, motor difficulties develop that may include ataxic gait, tremors in large and fine motor movement as well as in a resting state, and poor balance and coordination.
Language and Communication Delays in the development of language and communication skills are characteristic of children with Dravet syndrome. The parents of sixty-five children with Dravet syndrome participated in a voluntary informal survey about their children in 2005. One hundred percent of them reported that their children have difficulty with language and communication. Twenty-one percent reported aphasia, that is, their children’s early language development was normal or near normal, followed by regression, or a loss of language skills during their second or third year. Nearly half of the parents reported that their children had severe communication delays or were nonverbal. Thirty-eight percent reported either mild or moderate language delays. The remainder were unsure about the extent of their children’s language delays. Based on the observations of their parents, children with Dravet syndrome may have much better receptive language skills than expressive language skills.
Cognitive Development As in other areas, the early development of cognitive, or thinking and learning skills, seems to be normal. The appearance of cognitive delays seems to go hand-in-hand with that of delays in language and communication. On the face of it, there is some logic in this, as a great deal of our thinking and learning is mediated by language or communication skills. The language delays can also present a challenge for obtaining an accurate assessment of cognitive development because the children may not be able to express what they understand.
The developmental delays are also associated with the manifestation of seizures. Enough families report that their children’s development seems to stall between the ages of one and four, when seizure activity is usually at its most severe, to suggest a trend that needs further investigation. After the onset of seizures they struggle with meeting new developmental milestones and may regress, losing skills they had previously attained. Progress in cognitive development is highly variable from child to child and many of the children demonstrate splinter skills, that is, areas of their development that are significantly better or nearer to normal than most. For most children with Dravet syndrome, learning concepts such as the appropriate use of everyday objects, imitating and pretending, cause and effect, same/different, and quantities and time can become increasingly difficult. Maintaining appropriate focus is difficult. Children may have trouble following directions, especially if they have more than one or two steps. It can be difficult for them to see problems from more than one point of view. Learning colors, numbers, and letters may be very difficult.
Social Development One way that many parents first become aware of delays in social development is when their children do not demonstrate the expected stranger anxiety or separation anxiety that most typical children experience between the ages of one and three. Parents note that their children with Dravet syndrome lack a sense of appropriate social boundaries. They do not fear strangers and, in fact may be excessively affectionate toward strangers. Children with Dravet syndrome may have difficulty learning to imitate others’ behavior. Many tend toward solitary play and may engage in parallel play, but cooperative play is difficult and many do not understand turn-taking. Their ability to understand the concepts of ownership, belonging and others’ points of view may be difficult to assess, but based on parent reports, difficulties in these areas are common. Individuals with Dravet syndrome are likely to remain dependent on others for assistance with self-care skills such as toileting, dressing, and eating, often into adulthood.
Behavioral Development Ninety-five percent of the parents who participated in the fore-mentioned parent surveys reported that their children had some unusual behaviors. Those most frequently reported were perseveration or repetitive behaviors, flapping or clapping of hands, obsessions, excessive stubbornness, and excessive activity. Many parents also express concern for the safety of their children because of their tendency to wander.
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