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Disease Profile

Continuous spike-wave during slow sleep syndrome

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.


US Estimated

Europe Estimated

Age of onset





Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

Continuous spikes and waves during sleep; Continuous spikes and waves during slow-wave sleep; CSWS;


Congenital and Genetic Diseases; Nervous System Diseases


The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.

Orpha Number: 725

Continuous spikes and waves during sleep (CSWS) is a rare epileptic encephalopathy of childhood characterized by seizures, an electroencephalographic (EEG) pattern of electrical status epilepticus in sleep (ESES) and neurocognitive regression in at least 2 domains of development.

The prevalence is unknown. CSWS is a rare condition that affects 0.5-1.5% of children with epilepsy (in some series) and has a 3:2 male to female ratio.

Clinical description
CSWS is an age-related epileptic encephalopathy in which the clinical features evolve over time. After a normal or only moderately abnormal baseline development, seizures usually present at around 2-4 years of age. They are often unilateral, tonic-clonic or clonic and typically occur out of sleep. Seizures become more frequent, severe, and treatment-resistant with a marked deterioration in seizures, EEG, and developmental aspects (i.e. language, social interactions, global intelligence, motor skills and behavior) at approximately 5-6 years of age. During this acute stage, the seizures (absence seizures, clonic, tonic-clonic and others) and EEG abnormalities are difficult to control. Spontaneous improvement in seizures and EEG features occurs before puberty, but most patients remain with severe developmental delay.

Early developmental lesions such as vascular insults, especially affecting the thalamus, or malformations of cortical development have been found in approximately half of all cases. Genetic factors, especially mutations in the GRIN2A gene (16p13.2) have been recently linked to CSWS.

Diagnostic methods
Diagnosis is based on characteristic clinical evolution (with seizures and neurocognitive regression in at least 2 domains) and EEG findings. The main EEG feature of CSWS is ESES. ESES is characterized by marked potentiation of epileptiform discharges during the transition from wakefulness to sleep leading to (near-) continuous, bilateral or occasionally lateralized slow spikes and waves that occur during a significant proportion of non-rapid eye movement (REM) sleep. Magnetic resonance imaging (MRI) is performed in order to identify any brain lesions. As of now it is not routine clinical practice to perform genetic tests for GRIN2A in CSWS, but testing is available in certain specialized centers.

Differential diagnosis
Differential diagnosis includes any epileptic syndrome with sleep potentiation of epileptiform activity such as Landau-Kleffner syndrome, Panayiotopoulos and Gastaut types of benign childhood occipital epilepsy and rolandic epilepsy (see these terms).

Genetic counseling
An autosomal dominant transmission has been proposed in families with a GRIN2A mutation.

Management and treatment
The main aim of treatment is to control seizures. It is unknown whether improvement of EEG abnormalities improves the long-term developmental outcome. High-dose nocturnal benzodiazepines like diazepam or clobazam are successful in reducing epileptiform activity acutely and subacutely. The antiepileptic drugs most often used include valproate, levetiracetam, lamotrigine, and ethosuximide. Corticosteroids are useful but associated with long-term side effects. Epilepsy surgery is an efficacious therapy in selected cases, even when epileptiform discharges are bilateral.

Although seizures and EEG abnormalities tend to normalize by adolescence, the developmental prognosis is generally poor as neurocognitive regression is permanent in most cases.

Visit the Orphanet disease page for more resources.

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In-Depth Information

  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.