Given that seizure control in IS is more dependent on treatment than etiology, is an evaluation for etiology necessary? Children with IS due to tuberous sclerosis complex (TSC) have a greater likelihood of seizure freedom when treated with vigabatrin.3 Therefore, diagnosing TSC guides the decision of hormonal versus vigabatrin initial therapy. Do we need to go beyond clinical exam and neuroimaging to diagnose the presence or absence of TSC?