When to Suspect an SCN1A Mutation Related Epilepsy

Focal Epilepsy, Generalized Epilepsy, Lennox-Gastaut Diagnosis, Atypical Febrile Seizures and Epilepsy of Unknown Cause Beginning in Children < 1 year old:  When to Suspect an SCN1A mutation related epilepsy

A clinical study published in Brain 2007 (Harkin et al) reported from a multi-national study of 188 patients with epileptic encephalopathies (epilepsy with brain dysfunction) that 24% patients diagnosed with cryptogenic focal epilepsy and 22% patients diagnosed with cryptogenic generalized epilepsy had an SCN1A mutation , thus were a part of the Dravet syndrome spectrum (see Dravet syndrome).  The conclusion from this study was “A strong indicator for SCN1A analysis is an epileptic encephalopathy with seizure onset before 1 year of age, even if cognitive decline does not occur for several years thereafter. The social and economic benefit in making a definitive diagnosis in children with epileptic  encephalopathies cannot be underestimated. Neurologists continue to perform investigations looking for an etiology in children with cryptogenic encephalopathies such that establishing a definitive molecular diagnosis is cost-effective. More importantly, families are very grateful for a specific diagnosis especially with the treatment and genetic counseling implications that a SCN1A mutation carries.”

If your child has a diagnosis of focal or generalized epilepsy, Lennox-Gastaut, or Atypical Febrile Seizures AND had his or her first seizure prior to age 1 year,  even if development has remained typical in the first few years,  you may wish to discuss genetic testing with your child’s neurologist.  More specifically, SCN1A testing should be considered when an infant presents with first seizure < 12 months or medical history reveals:

  • Initial development, EEG, MRI and metabolic studies are normal
  • Development may remain typical until around age two years at which time decline or stagnation may occur
  • Clonic (contraction without stiffening) seizures on one side of the body that alternate with each seizure; myoclonic jerks (rapid contraction that may cause child to fall) often appear soon after first seizure; other seizure types appear over time and are not caused by fever or illness; atypical absence seizures (eyelid flutters or very long absence seizures) are common
  • Modest temperature elevation and illness are seizure triggers, especially in infants and toddlers ; photosensitivity may appear
  • Episodes are frequent, often prolonged (> 5 minutes) or status epilepticus (> 30 minutes), epilepsy is drug resistant
  • The following drugs make seizures worse:  phenytoin, fosphenytoin, carbamazepine, oxcarbazepine, lamotrigine, vigabatrin, tiagabine, rufinamide
See also  Dravet syndrome Case Study