Myoclonic-Atonic Seizures (Doose Syndrome)

Overview

  • Myoclonic-atonic seizures are the defining feature.
  • Frequent tonic seizures as the main seizure type is not usual in this syndrome.
  • The syndrome is considered an epileptic encephalopathy.
  • The EEG usually has a normal background particularly at onset of syndrome, with frequent generalised discharges of 2 to 3 Hz spike/polyspike waves.
  • Non-convulsive status epilepticus is a frequent feature.
  • Up to half of patients have a good outcome despite early refractory symptomatology.
  • Treatment usually involves high dose valproate in combination with other anticonvulsants.
  • Consider early referral to Paediatric Neurology.

According to the NICE Guideline: The Epilepsies:

  • The seizure type(s) and epilepsy syndrome, aetiology, and co-morbidity, should be determined.
  • If there is diagnostic uncertainty, individuals should be referred to tertiary services soon (within 4 weeks) for further assessment.

Demographics

Prevalence

  • ~1% to 2% of all childhood epilepsies.

Age at onset

  • 6 months to 6 years, peak 2-4 years.

Genetics

  • There is often a strong family history of epilepsy including other epilepsy syndromes.
  • A proportion of these patients are SCN1a positive.
  • SLC2A1 has also been found (Glucose Transporter gene)

Signs | Symptoms

Seizure semiology

Myoclonic astatic seizures are the defining symptoms (100%), manifesting with symmetrical myoclonic jerks immediately followed by loss of muscle tone (atonic component).  They cause lightning-like falls, head nodding, or bending of the knees.

  • More than half of patients have brief absence seizures, often together with myoclonic jerks, facial myoclonias, and atonic events.
  • Atonic and absence seizures are frequent and sometimes many occur each day.
  • Tonic seizures are not a major feature.
  • Non-convulsive status epilepticus for hours or days affects 1/3 of patients.
  • In 2/3's of patients, febrile and non-febrile generalised tonic clonic seizures appear first, several months prior to myoclonic astatic seizures.
  • The seizure frequency can become very severe and sometimes refractory to treatment. However, despite this, the outcome for most is favourable.

Neurological and mental state

  • Normal prior to the onset of seizures.

Differential diagnosis

  • Lennox Gastaut Syndrome.
  • Atypical childhood epilepsy with centrotemporal spikes
  • Dravet syndrome

Investigations

EEG

  • Usually normal background particularly at onset of syndrome, with frequent generalised discharges of 2 to 3 Hz spike/polyspike wave. With time background may show generalised slowing.
  • Epileptogenic activity increases in sleep.
  • Photic stimulation may trigger generalised spike/wave or myoclonic astatic seizures.
  • Non-convulsive status leads to continuous or discontinuous and repetitive 2 to 3 Hz spike/ wave.

Neuro Imaging

  • Symptomatic causes need to be excluded.

Prognosis

  • Half of patients (probably with the idiopathic form) achieve seizure freedom and normal development.
  • The others (probably symptomatic cases) continue with seizures, severe impairment of cognitive functions, and behavioural abnormalities.
  • Ataxia and motor linguistic disturbances may emerge.

Management

 Discussion with family

Resources

Epilepsy Action (UK) have information for Parents on Epilepsy with Myoclonic Astatic Seizures (Doose Syndrome)

References

  • Panayiotopoulos CP. The epilepsies: Seizures, syndromes and management: Based on the ILAE classifications and practice parameter guidelines. Chipping Norton, Oxfordshire: Bladen Medical Publishing; 2005.
  • Roger J, Bureau M, Dravet C, Genton P, Tassinari CA, Wolf P, editors. Epileptic syndromes in infancy, childhood and adolescence (4th ed).  Montrouge, France: John Libbey Eurotext Ltd ; 2005.