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 the most common paroxysmal events misdiagnosed as epilepsy.¹

• Misdiagnosis is common, but it is estimated that 0.8% of preschool children are affected.
• One study of children referred for "fits, faints and funny turns" found that 23% had one of the childhood epilepsies (with 48% of these having a specific epilepsy syndrome). Syncope was the commonest cause of a non-epileptic event (syncope and reflex anoxic seizures were diagnosed in 42%). 14% of the children were unclassified and managed without a diagnostic label or treatment.²
• Can occur at any age, but the peak age group is from six months to two years old.³
• Increased vagal tone tends to be familial.

• 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.

• Epilepsy: is frequently misdiagnosed.
• Causes of syncope in childhood include:³
  • Neurally mediated syncope
  • Reflex syncopes
  • Postural orthostatic tachycardia syndrome (POTS)
  • Pure autonomic failure
  • Multiple system atrophy
  • Cardiovascular causes
  • Cardiac arrhythmias
  • Structural heart disease
  • Non-cardiovascular pseudo-syncopes
  • Epileptic
  • Psychogenic

• Often diagnosed on the basis of the history and normal 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).⁴ This procedure is not usually necessary in order to make the diagnosis.

• Drug treatment is rarely, if ever, needed.
• Parents should be advised to place the child in the recovery position and avoid the natural tendency to pick up the child.
• Pacemaker insertion has been shown to be very effective but is rarely necessary.⁵
• Apart from pacemaker insertion, most other anti-syncope therapies are ineffective. Valproate and carbamazepine are effective in abolishing anoxic-epileptic seizures but do not influence the frequency of syncope.⁶
• Atropine has been tried if the attacks are very frequent, to reduce sensitivity to vagal influences.⁷

• Reflex anoxic seizures are benign.
• Child usually grows out of it, but it may occur later in life.