Many infantile seizures are subtle and lack declarative features seen in adults.⁸ This is particularly true of those arising from the temporal lobe: The infant may pause ongoing behaviors, appear to suddenly stop movement, and exhibit simplistic automatisms such as mouthing movements.²³ These are sometimes referred to as behavioral arrest, behavioral change, or hypomotor seizures. Oxygen desaturation may accompany these events, and if the child is connected to an oxygen saturation monitor, the change in the tone of the monitor may be the first sign alerting observers to the presence of the seizure. Parents reliably and quickly detect the peculiar change in the infant’s behavior, but others unfamiliar with the child’s habitual behavior may have difficulty identifying the onset of the event. There are almost never other declarative features of mature temporal lobe seizures: The infant is unable to vocalize the presence of an aura, cannot be asked about his or her experiences during the event to determine consciousness, does not exhibit contralateral dystonic hand postures, and does not show ipsilateral fine hand automatisms. Well-developed secondary generalization with synchronized clonic activity of both sides of the body is rare, particularly in the symptomatic epilepsies.¹⁴

Duchowny studied 14 infants <2 years of age with focal seizures and lateralized ictal electroencephalographic (EEG) abnormalities.⁹ Seizure semiology most frequently included behavioral arrest with forced head turning and tonic extension of the arms, sometimes accompanied by chewing, sucking, mouthing, or blinking. Yamamoto et al. compared focal seizures in 15 infants <2 years old with those in 23 children 3 to 13 years old.²⁵ They noted that the seizures in the infants were longer in duration and had simpler, predominantly oral automatisms.

Automatisms during partial seizures in infants and young children are usually subtle and predominantly oral, sometimes with simple gross motor movements of the proximal extremities.³ These contrast with the more complex fine motor behaviors seen in older patients. Jayakar and Duchowny noted an age-dependent evolution, with complex fine motor automatisms first appearing in their preschool group (2–6 years old).¹² A similar ontogeny was reported by Nordli et al.¹⁷ Karbowski et al. proposed the term temporal pseudoabsences to emphasize that decreased behavioral activity was more prominent than were automatisms in their infants with temporal lobe epilepsy.¹³ All of these results suggest a continuum in development of automatisms during childhood from simple to complex.

It can be extraordinarily difficult reliably to determine alteration of consciousness in most infants. For these reasons, the terms “simple” and “complex” are difficult to apply with any degree of certainty to most infantile seizures. The
gold standard in adult monitoring units for assessing consciousness is to ask the patient to follow commands, repeat phrases, and recall test items. None of these can be performed in the preverbal child. Inattentiveness, such as not turning the head to alerting stimuli, is not the same as altered consciousness.

Dravet and colleagues studied children with partial epilepsy that began before 3 years of age and used the term undetermined partial seizures for three patients in whom they experienced difficulty with this assessment.⁷ Duchowny accepted the term complex partial in this setting, under the assumption that some disturbance of consciousness must have occurred, based on unsuccessful attempts to influence attention by various maneuvers.⁹ In a study at the Cleveland Clinic Foundation of videotaped seizures from infants <2 years old with localization-related epilepsy, the authors found it impossible to be as confident about level of consciousness, despite similar attempts.¹ Nordli et al.¹⁶ reached the same conclusions, and Ohmori et al.¹⁸ found it difficult to apply the labels “simple” or “complex” definitively.