Neonatal seizures

Overview

A seizure is caused by sudden, abnormal and excessive electrical activity in the brain. By definition, neonatal seizures occur during the neonatal period — for a full-term infant, the first 28 days of life. Most occur in the first one to two days to the first week of a baby's life. Premature or low birth weight babies are more likely to suffer neonatal seizures.

Many of the visible signs of neonatal seizures — such as chewing motions and "bicycling" movements — also occur in healthy newborns. Therefore, testing is usually required to confirm the diagnosis.

The outcomes for babies who have neonatal seizures depend on the type of seizure and the underlying cause. Some neonatal seizures are mild and short-lived and therefore do not cause any lasting health problems. However, prolonged and untreated seizures can cause permanent damage due to decreased oxygen flow to the brain and excessive brain cell activity. Neonatal seizures are often symptoms of a more serious underlying condition, particularly brain injury. For this reason, babies experiencing neonatal seizures should receive rapid, specialized care.

About half of all babies who have neonatal seizures will develop epilepsy later in life. Those with seizures related to brain injuries or developmental abnormalities may have further complications, such as cerebral palsy, mental retardation and other neurological disorders. These conditions result from the underlying brain damage, not the seizure itself.

Causes

Neonatal seizures have a variety of causes. These include:

• Lack of oxygen before or during birth due to placental abruption (premature detachment of the placenta from the uterus), a difficult or prolonged labor, or compression of the umbilical cord
• Infection acquired before or after birth, such as bacterial meningitis, viral encephalitis, toxoplasmosis, syphilis or rubella
• Stroke before or after birth
• Blood clot in the brain
• Bleeding in the brain
• Brain birth defects
• Blood sugar or electrolyte imbalances
• Metabolic disorders such as maple syrup urine disease, pyridoxine dependency or phenylketonuria (PKU)
• Drug withdrawal, which may affect babies born to mothers addicted to barbiturates, alcohol, heroin, cocaine or methadone

In rare cases, neonatal seizures are caused by a condition called benign familial neonatal seizures, also known as fifth-day convulsions or fifth-day fits. This condition is inherited, and the baby's mother or father will also have had the disorder. Many babies with benign familial neonatal seizures develop normally, although some may have developmental delays that are seen in early childhood.

Signs & symptoms

Neonatal seizures can be difficult to diagnose because the seizure may be short and subtle. In addition, symptoms of neonatal seizures may mimic normal movements and behaviors seen in healthy babies.

Symptoms depend on the type of seizure — subtle, clonic, tonic or myoclonic.

Symptoms of Subtle Seizures

Subtle seizures are more common among full-term babies. Symptoms of subtle seizures include:

• Random or roving eye movements, eyelid blinking or fluttering, eyes rolling up, eye opening, staring
• Sucking, smacking, chewing and protruding tongue
• Unusual bicycling or pedalling movements of the legs
• Thrashing or struggling movements
• Long pauses in breathing (apnea)

Symptoms of Clonic Seizures

• Rhythmic jerking movements that may involve the muscles of the face, tongue, arms, legs or other regions of the body

Symptoms of Tonic Seizures

• Stiffening or tightening of the muscles
• Turning the head or eyes to one side, or bending or stretching one or more arms or legs

Symptoms of Myoclonic Seizures

• Quick, single jerking motions, involving one arm or leg or the whole body

Diagnosis

A test called an electroencephalogram (EEG) is essential for diagnosing and managing neonatal seizures. EEG records the electrical activity of the brain, and abnormalities on an EEG test (measured between seizures) can indicate a risk for seizures. However, babies with benign familial neonatal seizures usually have normal EEG readings.

Imaging tests of the brain, including magnetic resonance imaging (MRI) and computed tomography (CT) scan, are also used to determine the cause of seizures.

Treatment

Prompt diagnosis and treatment of neonatal seizures is essential. Your baby's health care team will also work to identify and treat any underlying cause of the seizures.

To control the seizures, anticonvulsant medications may be prescribed, including phenobarbital, lorazepam and phenytoin. Your baby will be closely monitored at all times while receiving these medications.

Babies suffering from hypoxic ischemic encephalopathy (not enough oxygen to the brain) may receive hypothermia treatment, which may reduce brain damage caused by the lack of oxygen. Hypothermic treatment involves cooling the baby's brain and body by a few degrees immediately after birth for several hours or days. Babies are closely monitored during treatment, and then slowly re-warmed to normal body temperature.