Why would my baby need MRI brain scans?

When brain injury is suspected in a newborn baby, brain scans are crucial for diagnosing and treating the injuries.

Brain scans, also referred to as brain imaging, show important information to diagnose and treat brain injuries and related medical conditions in a baby. Scans also help doctors assess a baby’s risk of having cognitive, developmental, or motor problems as they grow and develop. Predictions may be made about the child long-term, but quite frequently, the long-term effects of neonatal brain damage aren’t fully known until the child reaches school age and delays in their development become more evident.

A study published in The Journal of Pediatrics found that brain scans performed close to birth are better predictors of neurodevelopmental outcomes than scans done later. The early scans are essential because they help detect conditions that need to be medically managed right away, such as brain bleeds or edema (swelling). Brain imaging is especially important for premature babies who are at risk for neurodevelopmental impairment. However, any newborn – regardless of age – suspected of experiencing an injury to the brain during or near the time of birth must be assessed for brain injury.

Magnetic resonance imaging (MRI) and cranial ultrasonography (CUS) are common head imaging techniques that give doctors pictures of the baby’s brain and determine if important structures are injured. MRI and CUS can help diagnose injuries such as hypoxic-ischemic encephalopathy (HIE), brain bleeds, and hydrocephalus, which must be promptly treated.

Early intervention is critical for babies who experienced brain injuries and a lack of oxygen to the brain. The longer injurious brain conditions are left unmanaged, the higher the risk of permanent brain damage. However, because a newborn brain injury evolves over hours, days, and weeks, multiple brain scans are essential.

Often, brain injury in a newborn baby occurs during or close to the time of birth. Multiple scans performed at different times are necessary to fully understand a birth injury, since the injury can evolve over time.

When a brain injury is suspected, doctors will look for signs and symptoms of brain dysfunction, also known as neonatal encephalopathy. Signs and symptoms of brain injury are typically seen at 12 – 24 hours after birth, and brain swelling (edema) is usually evident at this time as well. When edema occurs in the first day or so after delivery, it is a strong indicator that the baby experienced a brain injury during or near the time of birth. An MRI can usually show moderate to severe forms of HIE within 24 hours of birth.

An MRI is best for assessing the extent of white matter brain damage, and it can usually show brain injury by 1 day of age. Once the initial brain damage is established in a baby, serial scans should be done so the medical team can evaluate the changing brain injury. Sometimes, radiologists miss evidence of brain damage on a scan or the damage may not be evident. Thus, it is not uncommon for scans to be performed frequently when a baby shows signs of a brain injury.

Brain bleeds (hemorrhages) in a baby can be diagnosed right away with CUS. An intraventricular hemorrhage (IVH) is a significant cause of brain injury in premature babies. Most cases of IVH take place within the first five days after birth. Some occur and can be detected before one hour of age. A subdural hemorrhage is the most common type of intracranial hemorrhage in newborn babies. When babies don’t have symptoms, a CUS performed for suspected head trauma or brain injury can easily detect this type of bleed. When a baby has symptoms of a subdural hemorrhage or hematoma, they usually occur within the first 24 – 48 hours of life. CUS helps the medical team determine the location and extent of brain bleeds in babies.

A subgaleal hemorrhage is one of the most serious types of brain bleeds in a baby and it is most frequently caused by a vacuum extraction or traumatic delivery. When a baby has a severe subgaleal hemorrhage, the head swelling may be evident right after birth, although swelling usually develops over a 12 – 72 hour period.  Computed tomography (CT scans) and MRIs are useful for differentiating a subgaleal hemorrhage from other cranial medical conditions.

Intraventricular hemorrhages can also lead to hydrocephalus, in which head swelling is caused by enlarged brain ventricles from problems with the flow of cerebral spinal fluid (CSF).  In a newborn, CUS is used for the initial diagnosis of hydrocephalus, but an MRI can better show the extent of the condition, especially the CSF pathway.  When a baby gets older and part of their soft spot closes, CUS can no longer be used, and CT or MRI must be performed for diagnosis and assessment of the baby’s hydrocephalus.  Hydrocephalus may be present at birth or shortly thereafter and must be quickly diagnosed and treated.

While these are critical examples, there are numerous conditions that can cause a baby to have brain damage. Prompt diagnosis of a brain injury is crucial so the medical team can undertake interventions to minimize or prevent permanent brain damage in the baby.

Brain injuries in a baby can be caused by many factors and are classified into different types. One of the most common causes of brain injury in a baby is birth asphyxia (a lack of oxygen to the baby’s brain during or near the time of birth).

Severe asphyxia is classified as either acute near-total asphyxia or acute-profound asphyxia. The first type usually causes injury to the deep gray matter of the brain, which affects many levels of the central nervous system. When the asphyxia is sudden and severe (acute near-total), deep structures in the brain, such as the basal ganglia, thalamus, and brain stem, are typically injured.

The following conditions can cause severe birth asphyxia in a newborn:

• Placental abruption
• Uterine rupture
• Prolapsed umbilical cord
• A very slow heart rate in the baby (bradycardia)

When the baby suffers asphyxia that is moderate to severe and relatively prolonged (acute-profound), injury will typically be seen in the cerebral cortex as well as the deep brain structures, particularly the putamen and thalamus.

Partial-prolonged asphyxia usually lasts for more than 30 minutes and it mainly causes injury in the watershed and parasagittal regions of the brain’s cortex, which are areas that do not have direct blood supply.

The conditions listed below can cause a baby to experience partial prolonged asphyxia:

• Use of the labor drugs Pitocin and Cytotec
• High blood pressure in the mother (hypertension)
• Low maternal blood pressure (hypotension), which can be caused by mismanaged anesthesia, maternal infection and dehydration
• Umbilical cord compression caused by a nuchal cord (cord wrapped around baby’s neck)
• Oligohydramnios (low amniotic fluid)
• Placental insufficiency
• Inadequate or delayed resuscitation of the baby at birth

Babies can also experience both severe birth asphyxia and partial prolonged asphyxia, which is referred to as a mixed brain injury pattern.

Yes, prompt delivery can prevent the baby from becoming injured. When a baby experiences an event that causes a lack of oxygen to their brain, the doctor should deliver right away via emergency C-section to minimize the time and severity of the asphyxia.

As soon as a mother is admitted to the labor and delivery unit, the baby’s heart rate should be monitored by a fetal heart rate monitor. If the baby starts to experience a lack of oxygen to their brain, the heart monitor will show non-reassuring tracings. The medical team must pay close attention to the tracings so they can intervene if the tracings become non-reassuring. Usually a prompt C-section delivery is the best intervention.