Infantile Spasms With a Normal Prior EEG
A 7-month-old girl is brought for clusters of brief flexor spasms that occur within 20 minutes of awakening, 8–10 spasms per cluster and 2–3 clusters per day for 3 weeks. Her developmental quotient has plateaued: she no longer rolls and has stopped babbling. A 30-minute awake EEG at an outside clinic was normal, and brain MRI without contrast was normal. Examination shows 6 hypopigmented ash-leaf macules and a 2-cm hypopigmented patch. Weight is 7.2 kg. The family has a 4-hour drive to your center and asks whether they can start medication before the EEG.
1. What is the most appropriate next diagnostic test, and why is the prior normal EEG insufficient?
Read the worked answer
The next test is prolonged video-EEG monitoring that includes sleep and captures the spasms. A 30-minute awake EEG can be normal in infantile spasms because hypsarrhythmia is often fragmented, state-dependent, and most apparent in sleep. The clinical history is highly suggestive: clustered flexor spasms on awakening, developmental plateau, and cutaneous findings of tuberous sclerosis. I would not start medication before capturing the events unless the child deteriorates, because treatment is prolonged and vigabatrin carries visual-field risk. The EEG should include the spasms and the sleep record; if no spasms occur, a longer study or home video is needed. I would also examine the skin under Wood lamp, obtain renal ultrasound and echocardiogram, and send TSC1/TSC2 testing.
2. If the EEG confirms hypsarrhythmia and spasms, what first-line treatment do you choose given the skin findings, and what monitoring is required?
Read the worked answer
With ash-leaf macules suggesting tuberous sclerosis, vigabatrin is the preferred first-line agent for infantile spasms. The reasoning is that TSC-associated spasms respond better to vigabatrin than to ACTH, and early control improves developmental outcomes. I would start vigabatrin and arrange baseline and periodic ophthalmologic examinations because of irreversible visual-field constriction; in an infant, this is monitored by examination and visual evoked potentials when feasible. I would also monitor for sedation, hypotonia, and rare MRI signal changes. If spasms persist after 2 weeks or the EEG remains hypsarrhythmic, I would add or switch to ACTH or oral corticosteroids rather than wait indefinitely. The family should be counseled that seizure freedom and EEG resolution are the treatment targets, not just fewer spasms.
3. At 6-week follow-up she has stopped spasms but has new focal motor seizures and developmental progress has stalled again. What is your next step?
Read the worked answer
I would reassess rather than simply add another medication. New focal seizures after infantile spasms suggest a structural lesion, especially a cortical tuber or focal cortical dysplasia, or a genetic epilepsy. I would obtain a prolonged video-EEG to characterize the focal seizures, an epilepsy-protocol MRI with contrast, and review the TSC genetic result. If a single epileptogenic tuber or dysplasia is identified and seizures are medically refractory, I would refer for epilepsy surgery evaluation, including PET or SPECT if MRI is ambiguous. I would also check vigabatrin adherence and adverse effects and consider switching to a broad-spectrum agent such as levetiracetam or clobazam. The key judgment is not to label this as recurrence of spasms alone; the new semiology changes the differential and the treatment pathway.