An infantile spasm can consist of something as simple and slight as a head drop or nod. These spasms may be subtle and can appear in different ways. According to the Epilepsy Foundation, the spasms may consist of: your baby suddenly stiffening their arms flinging out as their knees pull up and with them bending at the waist their head being thrown back as their legs stiffen and straighten repeated uncontrolled movements such as head bobs or body crunching