Knowledge on rare diseases and orphan drugs

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.

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.

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 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.

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

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.

Last update: April 2014 - Expert reviewer(s): Dr Tobias LODDENKEMPER - Dr Ivan SANCHEZ FERNANDEZ