Hypoxic Ischemic Encephalopathy (HIE)
What Is Hypoxic Ischemic Encephalopathy (HIE)?
Hypoxic ischemic encephalopathy (HIE) is a condition that happens when there is a loss of oxygen and/or reduced blood flow to the brain. It most commonly happens in the womb, or around the time of birth, and less commonly can be seen in childhood or adulthood. HIE causes injury to the brain which may cause seizures. In many cases, seizures may resolve as an infant recovers. However, in other cases, seizures may recur weeks to years later, and range in severity.
Most commonly, HIE occurs in newborns after a difficult birth. It may also occur after the child is born because of a severe heart problem or illness. This may lead to reduced blood flow, low oxygen levels, or very low blood pressure.
Other names for hypoxic ischemic encephalopathy include neonatal encephalopathy, perinatal hypoxia, or birth asphyxia.
How Common Is HIE?
HIE affects roughly 2-3 per 1,000 live births in the U.S., and 2-6 per 1,000 live births worldwide.
Seizures Associated with HIE
Babies with hypoxic ischemic encephalopathy (HIE) may have seizures within hours of birth. Sometimes, the seizures happen a day or two after birth. These seizures are usually focal onset and may affect different regions of the body. Seizures may be very subtle in many HIE cases. Often, the seizures can only be seen on EEG. Most of the time, seizures resolve after several days when children are treated with anti-seizure medication. Often, medication can be stopped shortly after birth without seizures happening again.
Sometimes, seizures happen again later because of the underlying brain injury. In such cases, seizures are most likely to develop in the first two years of life but may occur 10+ years after birth.
Seizures can manifest in many ways. One of the most concerning seizure types is infantile spasms. Infantile spasms typically happen between 4-8 months of age. In fact, HIE is the second leading cause of infantile spasms and Lennox-Gastaut Syndrome. If you are concerned your baby is having infantile spasms, seek medical attention immediately.
Other common seizure types can include:
- Tonic seizures
- Clonic seizures
- Absence seizures
- Focal onset impaired awareness seizures
Non-Seizure Symptoms of Hypoxic Ischemic Encephalopathy
Babies and children with HIE often have other medical problems in addition to seizures. These non-seizure symptoms of HIE may include:
- Cerebral palsy
- Speech and swallowing disorders
- Kidney issues
- Vision issues
- Digestive system issues
- Sensory processing disorder
- Learning and attention issues
- Dysautonomia (when the autonomic nervous system doesn’t work as it should), hearing issues, and growth and developmental delays
How Is HIE Diagnosed?
A diagnosis of hypoxic ischemic encephalopathy (HIE) is based on clinical and laboratory tests. Your healthcare provider will assess any concerns during the labor and delivery. Concerns may include fetal heart monitoring abnormalities, APGAR scores (a test to assess wellbeing of a newborn at birth), cord blood gases (if the HIE occurred at birth), MRI, physical exam, and EEG findings.
Learn More:Diagnosing Seizures and Epilepsy
How Is Hypoxic Ischemic Encephalopathy (HIE) Treated?
Initial treatment of more significant degrees of HIE right after birth is therapeutic hypothermia (cooling of the baby) for several days. Not all babies will have cooling. Most babies will be monitored with an EEG to detect seizures. Anti-seizure medication is usually required in the cooling phase. Many babies may stop anti-seizure medication by the time they leave the hospital if the medical team determines it is safe.
Treatment of seizures from HIE depends on the type of seizure and epilepsy syndrome. It may be best for children who continue to have seizures after taking two or more anti-seizure medications to get a referral to a Comprehensive Epilepsy Center to discuss other treatment options. In addition, it is important to pay attention to the child’s overall development and management of other associated medical problems. This can include early intervention, physical and occupational therapy, feeding problems, etc.
What Is the Outlook for Hypoxic Ischemic Encephalopathy?
Disclaimer: This field is rapidly evolving, and everyone has their own course. We are constantly learning about HIE, and published data may be slow to come.
Due to the variety of ways HIE can impact the brain, outcomes in both children and adults can range from mild to loss of life.
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