Sometimes the spasms of the seizure can be subtle, like head nods or wide eye opening with eye deviation. Often, the seizures look like a sudden bending forward at the waist as the arms and legs stiffen, usually lasting for one to two seconds, according to NORD, the National Organization for Rare Disorders. This can often be mistaken for a baby being sleepy, since the spasms can occur in transition time periods, like going to sleep or waking up. Some children arch their backs as they extend their arms and legs. Spasms often happen back to back or in multiple clusters, and can occur many times in one day. “It’s typical of a baby (who has IS) to have two to three clusters a day, lasting between 15 to 20 minutes,” Nordli said.