Paediatrics: Epilepsies: mid to late childhood (1)

2021-03-02 12:00 AM

These epilepsies are better described as genetic epilepsies. The diagnosis of epilepsy rests on history.

Epilepsies: mid to late childhood (1)

Idiopathic generalized epilepsies

These epilepsies are better described as genetic epilepsies. The diagnosis of epilepsy rests on the history. The EEG helps with classification. It should be remembered that generalized discharges on EEG (particular with photic stimulation) may occur in children without seizures. There is no need for MRI or blood tests after the first episode. Seizures include combinations of:

  • typical absences;
  •  myoclonia;
  •  tonic seizures and generalized tonicclonic seizures;
  •  myoclonic jerks.

 In these patients more than 80% of standard, and 95% of standard + sleep-deprived EEG recordings will show generalized discharges.

Myoclonic absence epilepsy

  •  Typical absences with short symmetrical jerks of mainly the upper limbs with abduction and elevation.
  • Early onset <5yrs of age.
  • EEG demonstrates generalized discharges of 3cycles/s spike and wave, that are not well formed and, in addition, may have short bursts of polyspikes.
  •  Poor prognosis and can deteriorate into an epileptic encephalopathy, may require treatment with the ketogenic diet.

Childhood absence epilepsy

  •  Previously known as ‘petit mal’.
  •  Typical absences only, but very frequent.
  •  Present during the first decade.
  • Rarely develop generalized tonic–clonic seizures.
  • Absences can be associated with mild myoclonia, asymmetry, or automatisms.
  • EEG demonstrates regular bursts of 3cycles/s spike and wave.

Juvenile absence epilepsy

  •  Onset towards the end of the first and during the second decade.
  •  All have absences.
  •  Up to 30% have myoclonic jerks.
  •  Majority develop generalized tonic–clonic seizures during second decade if untreated.
  • EEG discharges more fragmented and irregular than in childhood absence epilepsy, with more bursts of polyspike.

Prognosis is guarded even after many years of being seizure-free as an adult, relapse is common.

Juvenile myoclonic epilepsy

  •  Onset in the second decade.
  •  Invariable myoclonic jerks classically within the first hour of awakening.
  •  High risk of generalized tonic–clonic seizures, up to 80% of adolescent girls will have further generalized tonic–clonic seizures if they withdraw medication completely.
  •  EEG may have absences and photosensitivity; discharges are more fragmented and irregular than in juvenile absence epilepsy with bursts of polyspike.

 Treatment of idiopathic generalized epilepsies

  •  First-line: sodium valproate is normally used as first-line therapy, exceptin childhood absence epilepsy, where ethosuximide can be considered. In girls aged >9yrs, families should be counselled that it is up to twice as likely to produce seizure freedom as other drugs. Some experts (but not others) consider it may stimulate appetite and increase the incidence of polycystic ovary syndrome. Both of which reverse on drug withdrawal. All experts agree that it is significantly more teratogenic than other anti-epileptic drugs if taken during pregnancy at a dose of more than 1000mg per day.
  •  Second-line: lamotrigine is the next choice, but take note that it needsto be introduced more slowly when sodium valproate is being used concurrently.

Third-line: there is no consensus. Some clinicians advocate using benzodiazepine and suggest clonazepam as the most effective. However, it is extremely difficult to withdraw if it is used in moderate to high dosage. Therefore, others advise using clobazam, topiramate, or levetiracetam.