Infantile Spasms
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Direct answer
Infantile spasms, also called West syndrome, is an epileptic encephalopathy of infancy with brief flexor, extensor or mixed spasms that occur in clusters, usually between three and twelve months of age. The classic EEG finding is hypsarrhythmia, and developmental regression often accompanies the spasms. Treatment with ACTH or prednisolone, or with vigabatrin in tuberous sclerosis, is started urgently, because early control improves developmental outcome.
What you must remember
- Classic triad: infantile spasms, hypsarrhythmia on EEG and developmental arrest or regression.
- Spasm type: brief flexor, extensor or mixed jerks, with the trunk and arms flexing and the head nodding, commonly on waking and in clusters.
- Hypsarrhythmia: a chaotic, high-amplitude, multifocal EEG pattern, which sleep tends to accentuate.
- Aetiology: structural causes such as tuberous sclerosis, metabolic causes, hypoxic injury, and a cryptogenic group with no identified cause.
- First-line drugs: ACTH, oral prednisolone or vigabatrin, with vigabatrin preferred in tuberous sclerosis.
- Second-line options: ketogenic diet, sodium valproate and topiramate, used when first-line therapy fails.
- Vigabatrin toxicity: permanent concentric visual field constriction, so visual fields must be monitored.
A time-critical pathway from suspicion to treatment
Infantile spasms are easy to miss because the movements look like normal startle or colic. Early recognition and treatment shape the developmental outcome.
- Recognise the spasms: look for brief clusters of flexor or extensor jerks on waking, and video-record episodes for the neurologist.
- Record an EEG: a prolonged EEG with sleep recording shows hypsarrhythmia, which may need repeating if the first recording is normal, and it helps track response to treatment.
- Find the cause: MRI brain looks for cortical malformations and tuberous sclerosis, alongside metabolic and genetic testing.
- Examine the skin: hypomelanotic macules, ash-leaf spots and facial angiofibromas point to tuberous sclerosis complex, and a cardiac rhabdomyoma on echocardiography supports it.
- Start therapy: ACTH or prednisolone is started promptly, with vigabatrin chosen when tuberous sclerosis is present.
- Monitor response: check cessation of spasms, EEG normalisation and relapse, while watching for steroid adverse effects such as weight gain, hypertension and hyperglycaemia, and for vigabatrin visual toxicity.
Where the exam tries to catch you
Infantile spasms questions often hinge on recognising the event and choosing the right first drug.
- Trap: labelling clusters of spasms as colic or reflux. Correct: brief clusters on waking with developmental arrest suggest infantile spasms, and an EEG should be requested.
- Trap: choosing carbamazepine or phenytoin as first-line in infantile spasms. Correct: these drugs may aggravate spasms, and ACTH, prednisolone or vigabatrin are the first-line options.
- Trap: using vigabatrin without planning visual monitoring. Correct: vigabatrin can cause permanent visual field loss, so visual fields are monitored throughout treatment.
Frequently asked questions
What is the classic EEG finding in infantile spasms?
Hypsarrhythmia is the classic EEG finding in infantile spasms, a chaotic, high-amplitude pattern with multifocal spikes and slow waves. It is seen between spasms and supports the diagnosis when it accompanies the clinical triad.
Which drugs are first-line for infantile spasms?
ACTH, oral prednisolone and vigabatrin are the first-line drugs for infantile spasms. Vigabatrin is preferred when tuberous sclerosis complex is the cause, while hormonal therapy is used more widely otherwise.
Why is vigabatrin monitored in infants?
Vigabatrin can cause permanent concentric visual field constriction, so visual fields must be monitored throughout treatment. The toxicity can be permanent even though the drug is effective, which is why monitoring is essential.
What is the prognosis of infantile spasms?
Infantile spasms carry a risk of developmental delay and later epilepsy, and outcome is better when treatment starts early. Spasms may relapse, and some children later evolve into other epilepsies such as Lennox-Gastaut syndrome.
Which conditions commonly cause infantile spasms?
Structural brain malformations, tuberous sclerosis complex, hypoxic-ischaemic injury and inborn errors of metabolism are common causes of infantile spasms. In many children no cause is identified, and this is called cryptogenic infantile spasms.