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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.
- Reflex anoxic seizures occur mainly in young children (infants and preschool children) but can occur at any age.
- 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 most common 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.
- They can occur at any age; however, the peak age group is from 6 months to 2 years.
- 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:
- 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.
- Reflex anoxic seizures can usually be managed just with reassurance. 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 is the only definitive treatment and is only used for frequent, severe cases.
- 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.
Reflex anoxic seizures are benign. The child usually grows out of it.
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Further reading & references
- STARS; Syncope Trust and Reflex Anoxic Seizures
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