Reflexic anoxic seizures

Synonyms: pallid syncopal attack, white breath-holding attacks

Reflex anoxic seizures are paroxysmal, spontaneously-reversing brief episodes of asystole triggered by pain, fear or anxiety. Anoxic seizures are non-epileptic events caused by a reflex asystole due to increased vagal responsiveness. They are often misdiagnosed as epilepsy.

Epidemiology

• Reflex anoxic seizures occur mainly in young children (infants and preschool children) but can occur at any age¹ .

• Misdiagnosis is common but it is estimated that 0.8% of preschool children are affected.

• They can occur at any age; however, the peak age group is from 6 months to 2 years² .

• Increased vagal tone tends to be familial.

Presentation

• During the episode, the child becomes suddenly pale and limp, will fall if standing and loses consciousness.

• This is followed by stiffening and clonic jerking of the limbs.

• The episode is usually brief (30-60 seconds) and recovery is rapid.

• There may also be upward eye deviation and urinary incontinence.

• On recovery, the child may feel tired and washed-out for some time.

• Reflex anoxic seizures do not cause tongue-biting and this may be useful in the differentiation from epilepsy.

Differential diagnosis

• Epilepsy is frequently misdiagnosed.

• Causes of syncope in childhood include² :
  

  • Neurally mediated syncope.

  • Reflex syncopes.

  • Postural tachycardia syndrome (PoTS).

  • Pure autonomic failure.

  • Multiple system atrophy.

  • Cardiovascular causes.

  • Cardiac arrhythmias.

  • Structural heart disease.

  • Non-cardiovascular pseudo-syncopes.

  • Psychogenic syncope.

Investigations

• Often diagnosed on the basis of the history and normal electroencephalogram (EEG).

• ECG: exclude a long QT interval, pre-excitation, heart block or ventricular hypertrophy.

• Vagal excitation tests, while under continuous EEG and ECG monitoring (ocular compression induces the oculo-cardiac reflex). This procedure is not usually advised or necessary in order to make the diagnosis in children.

Management

• Reflex anoxic seizures can usually be managed just with reassurance. Drug treatment is usually not needed.

• Parents should be advised to place the child in the recovery position.

• Pacemaker insertion is the only definitive treatment and is only used for frequent, severe cases^{3 4} .

• Apart from pacemaker insertion, most other anti-syncope therapies are ineffective.

Prognosis

Reflex anoxic seizures in childhood are usually benign such that the child grows out of it.