2. Clinical features
Onset is always within the first year of life, with a peak age at 5 months,
affecting previously normal children.
Twice as many boys are affected.
Dravet syndrome is characterised by a tetrad of seizures, which is seen in
more than half of cases:
1. Early infantile febrile clonic convulsions
2. Myoclonic jerks
3. Atypical absences
4. Complex focal seizures
Convulsive, myoclonic or absence status epilepticus are frequent.
3. the first period is relatively mild (the pre-seismic period), it lasts for 2
weeks to 6 months and manifests mainly with febrile clonic convulsions.
mainly unilateral and less often generalised.
usually longer than a typical febrile seizure.
In 3/4th of pts seizures are usually provoked by hyperthermia of around
38°C, minor infections, immunisations or hot baths.
The remaining 1/4th of pts have non-febrile seizures.
seizures recur frequently within 6–8 weeks.
4. The second period is relentlessly aggressive (the seismic period)
there is emergence of other multiple-seizure types and severe
neurocognitive deterioration.
It develops between the second and sixth years.
Various forms of febrile and non-febrile convulsive seizures, myoclonic
jerks, atypical absences and complex focal seizures occur on a daily basis
and frequently evolve to status epilepticus.
The signs consist of hypotonia, ataxia (60%), pyramidal signs (20%),
uncoordinated movements, and interictal myoclonus.
5. The third period is static (the post-seismic period). The seizures may
improve, but serious mental and neurological abnormalities are
irreversible.
6. Provocating factors
Hyperthermia (febrile illnesses, warm environment, hot baths) is a
frequent precipitating factor, particularly at onset of seizures, but this may
continue in adolescence (‘febrile seizures plus’).
Febrile epilepticstatus can occur up to adulthood.
Photic and pattern stimulation, movements and eye closure precipitate
GSWD, myoclonic jerks and absence seizures.
A quarter of patients have self-induced seizures by hand waving or
pattern stimulation.
7. Aetiology
Dravet syndrome is mostly genetically determined, but the mode of
inheritance is unknown.
Approximately half of patients have a family history of various epileptic
syndromes and mainly febrile seizures.
Mutations in the voltage-gated sodium channel gene SCN1A were found
in a high percentage (range 35–100%) of pts with Dravet syndrome.
8. Diagnosis
There is no metabolic abnormality.
Tissue biopsies are normal.
Genetic testing: a severe SCN1A gene defect, if present, is strongly
supportive but not diagnostic of Dravet syndrome.
Brain CT and MRI scans are either normal or show mild cerebral or
cerebellar atrophy.
Functioning brain imaging may be normal or show focal hypoperfusion
and hypometabolism, even when the MRI is normal.
9. Diagnosis-EEG
The inter-ictal EEG may initially be normal, but 20% show generalised
photoparoxysmal responses.
Within 1 year the EEG becomes very abnormal in 2/3rd of pts.
Brief asymmetrical paroxysms of poly spike/spike–slow-wave discharges
(GPSWD) usually dominate the EEG.
Focal and mainly multi-focal abnormalities of sharp or slow spike-waves are
frequent.
Photoparoxysmal discharges occur in 40% of patients but persist in less than
5%.
Eye closure and pattern stimulation also induce generalised discharges and
myoclonic jerks.
10.
11. D/D
1. the benign (idiopathic) myoclonic epilepsy in Infancy
the first events are brief generalized myoclonic seizures, which remain the
only ictal manifestations even without treatment.
EEG studies always show generalized SWs concomitant with the jerks.
Seizures are pharmacoresponsive, development is normal and prognosis is
favorable.
The reflex form with contact-induced myoclonic seizures recover
spontaneously.
12. d/d
2.Progressive myoclonus epilepsy, mainly ceroidlipofuscinosis,
It can be ruled out by absence of visual loss, fundus abnormalities, and
negative results of biologic investigations.
3.The Lennox-Gastaut syndrome is virtually excluded by
a history of febrile clonic seizures in the first year of life.
Its characteristics are different: frequent lesional etiology, later onset, drop
attacks, atypical absences, axial tonic seizures.
specific electroencephalographic abnormalities in LNG shows diffuse slow
spike-waves and rapid, highvoltage rhythms during sleep.
13. 4. The epilepsy with myoclonic–astatic seizures (Doose syndrome) is
defined by the association of GTCS and frequent ‘‘drop attacks,’’ which are
unusual in Dravet syndrome.
as a rule, it starts after the age of 2 years
Atypical absence status with myoclonic jerks occurs, but there are no focal
seizures and no focal EEG abnormalities.
Outcome is variable with complete cure in >50% of the cases
14. TREATMENT
Seizures are intractable. AEDs may reduce them but do not control them.
in convulsive seizures
1. Valparin
2. Benzodiazepenes
3. Phenobarbitone
in absence and myoclonic seizures, ethosuximide is beneficial.
Carbamazepine & Lamotrigine are contraindicated.
newer AEDs:
1. topiramate
2. zonisamide
3. levetiracetam
4. Stiripentol - licensed in 2009 to use in conjunction with CLB and VPA as
adjunctive therapy for refractory GTCS in Dravet syndrome.
A ketogenic diet is beneficial, starting as early as possible.
