A newborn seizure involves an episode of sudden, abnormal, and excessive electrical activity in the brain that occurs within the first 28 days of life. Rapid identification and intervention are required because prolonged or untreated seizures can potentially cause permanent damage due to excessive brain cell activity and decreased oxygen flow. While seizures in older children and adults often involve dramatic, full-body convulsions, a newborn’s immature nervous system means their seizures usually present in ways that are far more subtle and easily missed.
Why Newborn Seizures Are Difficult to Identify
The primary challenge is that newborn seizures rarely resemble the dramatic, generalized shaking seen in older individuals. The developing brain of a newborn, especially a premature infant, has not yet formed the widespread, synchronized connections necessary for a full-blown tonic-clonic seizure. Because of this immaturity, the abnormal electrical discharge often remains localized, producing highly specific, small-scale movements.
Seizures in this age group are commonly focal, meaning they affect only a specific part of the body. These subtle signs may mimic the normal, erratic movements or behaviors typical for a healthy newborn. Visible signs, such as chewing motions or bicycling movements, can also occur in a baby who is not having a seizure, making the distinction difficult without specialized testing. These seizures are often symptoms of a more serious underlying condition, such as a brain injury or infection.
Categorizing the Physical Signs of Seizures
Newborn seizures are generally categorized into four main types based on their physical presentation, with the most common being the most challenging to recognize.
Subtle Seizures
Subtle seizures are the most frequent type and the hardest to distinguish from normal activity. They often involve eye-related phenomena, such as rhythmic eye deviation to one side, sustained staring, or rapid fluttering or blinking. Oral movements are also common, including repetitive sucking, smacking, or chewing motions.
Other manifestations include unusual, rhythmic limb movements, such as paddling with an arm or bicycling with the legs. A long pause in breathing, known as apnea, can occasionally be the only observable sign of a subtle seizure, though this is rare. These fragmented movements result from the way the newborn brain channels the electrical discharge, often involving primitive brain stem and subcortical structures.
Clonic Seizures
Clonic seizures involve rhythmic jerking, often focal, affecting a specific body part, such as one arm, one leg, or one side of the face. The movements are rhythmic and repetitive, occurring at a rate of approximately one to four times per second. This activity may sometimes migrate from one limb to another, a phenomenon known as a “Jacksonian march,” though this is uncommon in newborns.
Tonic Seizures
Tonic seizures are characterized by a sudden and sustained stiffening or posturing of the body. This may involve the whole body, leading to a rigid or tense appearance, or be localized to a single limb or the trunk. The sustained posturing can sometimes mimic decerebrate or decorticate posturing, which indicates severe brain dysfunction.
These stiffening episodes frequently occur while the baby is asleep and typically last for a short duration, often less than 20 seconds. Tonic seizures can be difficult to treat with standard anti-seizure medications and do not always show corresponding electrical activity on a standard electroencephalogram (EEG).
Myoclonic Seizures
Myoclonic seizures present as very brief, shock-like jerks involving a single muscle or a group of muscles. They are rapid, isolated movements that can be focal or multifocal. These seizures can be difficult to differentiate from the benign startle reflex, a normal response in newborns to sudden stimuli.
If these jerks are massive and frequent, they can suggest a more severe underlying brain injury. However, benign neonatal sleep myoclonus, which consists of rhythmic jerking only during sleep, is a common, harmless condition that must be distinguished from true myoclonic seizures.
Differentiating Seizures from Normal Jitteriness
Newborns commonly exhibit non-seizure movements, such as jitteriness or tremors, that can be mistaken for seizure activity. Jitteriness involves rapid, fine, and symmetrical tremulous movements of the hands, feet, or face. These movements are often triggered by external factors like being unwrapped, stimulated, or crying.
The most important clinical test to differentiate benign jitteriness from a true seizure is the suppression test. Jitteriness can be stopped or suppressed by gently holding or flexing the affected limb. In contrast, true clonic or myoclonic seizure activity cannot be interrupted by physical restraint or repositioning.
Jitteriness is not associated with abnormal eye movements or changes in the baby’s vital signs. Seizures are often accompanied by autonomic changes, such as alterations in heart rate or breathing patterns. When in doubt, any repetitive or stereotypical event should be treated as a possible seizure until confirmed otherwise by a medical professional.
Immediate Action and Next Steps
If a caregiver suspects a newborn is experiencing a seizure, the situation is urgent and requires immediate attention. The first action is to ensure the baby’s safety by placing soft padding around them and moving any hard objects out of the way. Do not attempt to restrain the baby or place anything in their mouth, as this can cause injury.
Contacting emergency medical services immediately is the most important step for suspected seizure activity. While waiting for help, caregivers should note the precise time the event started and stopped, the duration, and a detailed description of the movements observed. If possible, a video recording of the event can be an invaluable tool for the medical team in making a diagnosis.
Upon arrival at the hospital, the medical team will stabilize the baby and begin an evaluation, which often includes checking blood glucose levels, as metabolic issues can trigger seizures. The definitive diagnostic tool is the electroencephalogram (EEG), a non-invasive test that records the electrical activity of the brain. An EEG confirms the presence of abnormal electrical discharges and differentiates true seizures from non-epileptic movements.