Medical InformationDiagnosis & Testing
DIAGNOSIS & TESTING
While a diagnosis of Dravet syndrome is made clinically, up to 80% of cases will also test positive for an SCN1A gene mutation, helping to confirm diagnosis. It is important to note that the absence of an SCN1A mutation does not exclude diagnosis. Genetic testing is commercially available in most countries. Upon receiving a positive genetic test result, parents may also be tested to establish inheritance.
Clinical Diagnostic Criteria
Dravet syndrome is diagnosed clinically based on seizure history, clinical aspects, neurologic examination, EEG pattern and observation. Subsequently, genetic testing of the SCN1A gene can confirm the diagnosis in the majority of cases. However, a mutated SCN1A gene cannot be identified in approximately 20% of the patients who meet the diagnostic criteria of the syndrome. Therefore it is possible that other genes might be involved.
Earmarks of the syndrome include:
- Seizures of various types beginning in the first 12 months of life
- Seizures begin as febrile, but later also appear without a fever
- Episodes of status epilepticus (prolonged seizures)
- Seizures do not respond to standard anticonvulsant drugs
- Initial development is normal, then slows or stagnates in the second year of life
- Myoclonic seizures occur around the age 18 months of age
- Seizures associated with vaccinations, hot baths, or warm temperatures
There are now commercially available blood tests which can screen for an SCN1A gene mutation that may be ordered by your doctor. However, current technology may not detect all mutations. Some screening labs also test for SCN2A, GABRG2, and PCDH19 mutations that may cause Dravet syndrome and related epilepsies. Consultation with genetic counselor is available for families through some labs.
NEXT: Genetic Mechanisms