Dravet syndrome: the long-term outcome

Abstract

Few studies focused on the long-term outcome of Dravet syndrome in adulthood are available in the literature, but all are concordant. In this article, we consider the outcomes of 24 patients followed at the Centre Saint-Paul, Marseille, up to the age of 50, and compare them to the patients reported in the literature. Five patients (20.8%) died, at a mean age of 24.8 years, one by status epilepticus, three by sudden unexpected death in epilepsy (SUDEP), and one of unknown cause. Epileptic seizures tend to become less frequent and less severe after childhood. Fever sensitivity (temperature variations) persists throughout the clinical course of DS, but its impact on seizure frequency and severity is milder than in infancy. Generalized convulsive seizures, mostly reported as generalized tonic-clonic seizures (GTCS), were the only seizure type observed in almost all of the patients, often with a focal onset. They are less frequent than in childhood and mostly nocturnal. Some of these major convulsive seizures have less typical aspects, for example, bilateral or asymmetric tonic posturing, followed in some cases by a tonic vibratory state or clonic movements (Oguni et al., Brain Dev 2001;23:736-748; Akiyama et al., Epilepsia 2010;51:1043-1052). Other seizures like myoclonic seizures, atypical absences, and complex partial seizures (CPS) are less common in adulthood: Among our 24 patients, only 6 had atypical absences, and one myoclonic and one complex focal seizures. Electroencephalography (EEG) also changes with age but is still multiple and heterogenous, interictally and ictally. Photosensitivity and pattern sensitivity also showed a tendency to disappear before the age of 20. Motor abnormalities are common. Cerebellar features, including ataxia, dysarthria, intention tremor, and eye movement disorder, become more prominent. Walking is markedly impaired, often due to orthopedic signs such as kyphosis, kyphoscoliosis, flat feet, or claw feet. This symptomatology was minor during childhood and worsened during and after adolescence, despite physiotherapy. Mental retardation ranged from moderate to severe, with predominance of language impairment, and some patients had a major personality disorder, labeled autistic or psychotic. Dependency in adulthood is nearly constant: Only 3 of our 24 adult patients lived independently.