Neonatal seizures are sudden, involuntary disruptions of the brain’s electrical activity occurring in a newborn. The incidence of seizures is higher during this period than at any other time in life, reflecting the unique vulnerability of the developing central nervous system. The newborn brain is immature, making it highly susceptible to electrical misfires. This heightened susceptibility is due to a natural imbalance where the brain’s excitatory circuits are relatively mature, while the inhibitory circuits, which normally quiet electrical activity, are still developing.
Recognizing Neonatal Seizures
Seizures in newborns often manifest in ways that are different from those seen in older children or adults. They rarely present as the generalized convulsions typically associated with the condition, making them difficult to recognize. Instead, a newborn’s seizures are frequently subtle and fragmentary, involving only small groups of muscles or specific movements.
These subtle signs include rhythmic, repetitive movements such as eyelid fluttering, sustained eye deviation, or uncontrollable eye rolling. Other common presentations involve automatisms of the mouth and face, such as repeated sucking, smacking, or tongue thrusting. Subtle motor activity may also appear as unusual cycling motions of the legs or swimming-like movements of the arms.
A particularly concerning sign is apnea, which is a prolonged pause in breathing. Because these movements can sometimes mimic normal newborn behaviors, medical confirmation is needed to distinguish true seizures from non-epileptic events like jitteriness or benign sleep movements.
Causes Related to Birth Injury and Oxygen Deprivation
A lack of sufficient oxygen or blood flow to the brain around the time of birth is the most frequent cause of seizures in full-term newborns. This condition, known as Hypoxic-Ischemic Encephalopathy (HIE), is a form of brain injury resulting from an oxygen deficit. HIE is a common underlying factor, accounting for a large percentage of seizures that begin in the first 72 hours of life.
The mechanism involves the failure of the brain’s energy-dependent systems when oxygen supply falters. This energy failure causes neurons to depolarize excessively, leading to synchronized, uncontrolled firing that results in a seizure. The severity of the oxygen deprivation directly correlates with the likelihood and persistence of seizure activity.
Bleeding within the brain, or intracranial hemorrhage, is another injury-related cause, particularly in premature infants. Intraventricular hemorrhage (IVH), bleeding into the fluid-filled spaces of the brain, is seen more often in very low birth weight babies. The presence of blood irritates the surrounding brain tissue, lowering the seizure threshold and triggering abnormal electrical discharges.
Another cause is an ischemic stroke, where a blood clot blocks a vessel, cutting off blood supply to a specific area of the brain. When blood flow is obstructed, the affected brain cells die off, and the resulting injury site becomes a focus for excessive electrical activity. Depending on the location of the stroke, these seizures are typically focal or restricted to one side of the body.
Causes Related to Metabolic Imbalances and Infection
The brain relies on a stable internal chemical environment, and imbalances in key substances can provoke seizures. Low blood sugar, or hypoglycemia, is a significant trigger, particularly in infants born to diabetic mothers or those who are small for their gestational age.
Abnormal levels of electrolytes can also disrupt neuronal signaling. Hypocalcemia (low calcium) and imbalances in sodium (hyponatremia or hypernatremia) can destabilize the electrical potential of brain cells. Correcting these specific electrolyte levels often stops the seizures without the need for long-term anti-seizure medication.
Infection is another major category of acute symptomatic seizures, where systemic illness or inflammation directly affects the central nervous system. Meningitis, an infection of the membranes surrounding the brain and spinal cord, and sepsis, a widespread bacterial infection, can lead to seizures through inflammation and direct irritation of brain tissue. These infections must be ruled out because delaying treatment can lead to rapid and severe neurological damage.
Newborns exposed to certain substances in utero may experience seizures as part of Neonatal Abstinence Syndrome (NAS). When the infant is no longer receiving the substance after birth, the resulting withdrawal can trigger neurological hyperexcitability. The seizure is a symptom of the body’s acute reaction to the sudden absence of the drug.
Structural and Inherited Causes
Some seizures in newborns are not due to an acute injury or metabolic crisis but rather to a pre-existing condition involving the brain’s physical structure or genetic code. Structural brain malformations occur when the brain does not develop correctly during gestation. Conditions like cortical dysplasia involve areas where the neurons are disorganized, creating an inherent source of electrical instability.
Other structural causes include lissencephaly, where the brain surface lacks its normal folds, or polymicrogyria, which involves an excessive number of small, irregular folds. These structural anomalies disrupt the normal circuitry, making the infant prone to seizures that are often resistant to standard medications.
In some cases, the seizures are due to specific genetic errors that affect the function of ion channels, the proteins that control electrical signals in the brain. These inherited epilepsy syndromes can present in the neonatal period. An example is Benign Familial Neonatal Seizures, which typically resolves on its own within the first few months of life.
Inborn errors of metabolism, such as certain organic acidemias, also fall into this category. A genetic defect prevents the body from properly processing specific chemicals, and the resulting accumulation of toxic metabolites disrupts brain function, leading to seizures. Identifying these causes is important because some, like those related to vitamin B6 metabolism, can be treated with targeted dietary or supplement therapy.
Diagnosis and Initial Medical Steps
The cornerstone of diagnosing a true neonatal seizure is the Electroencephalogram (EEG), which measures the electrical activity of the brain using electrodes placed on the scalp. Continuous video-EEG monitoring is the preferred method, as it confirms whether subtle movements correlate with abnormal electrical discharges. This monitoring is important because some critically ill newborns experience electrical seizures without any visible clinical signs.
Once a seizure is confirmed, the medical team simultaneously investigates the underlying cause. Initial steps involve rapid laboratory testing, including a check of blood glucose levels and a comprehensive electrolyte panel to identify metabolic issues. A lumbar puncture, or spinal tap, is often performed to collect cerebrospinal fluid, which is analyzed to rule out central nervous system infection like meningitis.
Brain imaging, such as a cranial ultrasound or a Magnetic Resonance Imaging (MRI) scan, is also performed to look for structural injuries like hemorrhage, stroke, or malformations. Initial treatment focuses on stabilizing the infant and stopping the seizure activity to minimize potential brain damage. The first-line anti-seizure medication often used is Phenobarbital, administered intravenously, with Levetiracetam or Lorazepam reserved for seizures that continue despite initial treatment.
If a specific underlying cause is identified, the immediate treatment is directed toward correcting that problem. For example, if low blood sugar is the cause, an intravenous glucose solution is given, or if an infection is found, broad-spectrum antibiotics are started immediately. The long-term management and prognosis depend heavily on the specific cause of the seizures.