A subtle seizure in a newborn is characterized primarily by which of the following symptoms?

A subtle seizure in a newborn is primarily characterized by eye deviations, which can include gaze direction changes such as rolling or fluttering. These types of seizures are often less obvious than other forms of seizure activity and can be mistaken for normal behavior or other non-seizure movements.

In newborns, subtle seizures can manifest through brief episodes where the infant appears to be staring or has abnormal eye movements, such as deviation of the gaze. This symptom is key in identifying subtle seizures, particularly because they may not involve the more dramatic motor activity seen in other types of seizures, such as jerking or tonic posturing.

Other choices, while they may be associated with seizures in different contexts, do not adequately represent the primary characteristics of subtle seizures in newborns. Repetitive jerking is more indicative of myoclonic seizures, tonic limb extension typically implies more severe seizure types, and flexion of the arms is usually associated with other seizure forms or movements rather than being characteristic of subtle seizures. Therefore, the presence of eye deviations makes it clear that this choice accurately captures the essence of what constitutes a subtle seizure in a newborn.