Imaging The Term Neontal Brain Flashcards
When is brain imaging indicated in infants?
Neonatal encephalopathy Seizures Unexplained apnea’s Infections Metabolic disorders Birth injuries Suspected brain abN
What are the advantages of US
No ionizing radiation Portable Readily available Easily repeated Economical No special preparation Can measure cerebral blood flow
What are the limitations of U/S
May not visualise convex surfaces or the posterior fossa well
User dependent
What are the limitations to CT
Less likely to detect injuries to deep gray nuclei, brain stem and cerebellum
Less likely to detect strokes
Ionizing radiation required
Poor gray/white matter contrast due to lack of myelination
What does fat and water look like on MRI in
- T1 weighted images
- T2 weighted images
- Water = dark, fat = light
2. Water = lighter
What is MRI-DWI
Measures motion of water molecules when magnetic gradient is applied
Following cytotoxic oedema there is impaired movement of water molecules leading a diffusion restriction = allows calculation of apparent diffusion coffieicnet
How are the apparent diffusion cofficient maps used
Determines site and extent of injury
- diffusion restricted areas = low ADC
appear brighter on DWI, appear darker on ADC maps
What biochemical compound metabolism is assessed with MRS
N-acetylaspartate (NAA) = decrease with dysfunction/death
Lactate = increase with energy source failures
What are the advatnages to MRI for newborn brain imaging?
More sensitivity and specific for detecting brain abN
No ionizing radiation
Better diagnostic accuracy and patient safety
Few contraindications
More availability of MRI compatible equipment
Can help understand extent of injury, and scope of recovery and repair possible
What is neonatal encephalopathy?
A clinically defined syndrome of disturbed neurological function in the earliest day of life in the term infant
What are clinical features of NE
Apnea
AbN tone and reflexes
Altered consciousness
Seizures
What are causes of NE
HIE IEM Infection Bilirubin toxicity Metabolic disturbances Cerebral dysgenesis Stroke
What patterns of injury are seen in HIE
Watershed
Basal ganglia/thalami
What are watershed injuries?
Affect areas between brain’s major arterial supplies, and deep in sulci leading to cortical edema/necrosis/infarction
Associated with prolonged partial HIE
How does watershed injury look on imaging
Day 3-5d MRI: restricted diffusion, lactate peak in watershed regions, T1/2 may be normal
Day 10-14: Maximal injury on T1/T2
- see increased signal intensity on T1 weighed
What are basal ganglia/thalamic injuries?
Seen in acute, profound HIE
Injury in the areas with highest metabolic rate and need for energy substrates
How does basal ganglia/thalamic injuries look on imaging
Day 3-5d MRI: restricted diffusion with hyper intense signal, lactate peak in regions, T1/2 may be normal OR if severe may see hyper intense signal already on T1
Day 10-14: Maximal injury on T1/T2
- see increased signal intensity on T1 weighed
What are typical findings on MRI for basal ganglia/thalamic injuries
Higher signal intensity on T1 in basal ganglia (seen early at day 3-5)
Later higher signal intensity in the ventro-lateral nuclei of the thalami
Loss of normal signal intensity in the posterior limb of the internal capsule
How many infants have watershed lesions, basal ganglia/thalamic lesions and normal MRI
watershed lesions = 52%
basal ganglia/thalamic lesions = 22%
normal MRI = 26%
With a known sentinel event - more have basal nuclei damage
What can you see if there’s severe HIE ?
Effacement of sulcal markings
Closure of Sylvia fissures
Narrowing of interhemispheric fissures
Compression of anterior horns of lateral ventricles
- may be seen on CT, MRI, US
What type of MRI imaging is most sensitive for acute brain injury in the first 3 days of life
DWI
When can imaging be done HIE
- MRI + DWI + MRS: day 3-5 to diagnosis, repeat at date 10-14 if not consistent examination or if dx ambiguity
- U/S - day 1 of life can see significant brain injury, at 24-36 with Doppler can see rebound cerebral blood flow (more so in moderate-severe watershed injuries)
- CT: 72 +/- 12 hours after suspected insult - can see increasing edema, best sees basal ganglia/thalamic injury or total injury, may underestimate severity of white matter and cerebral cortex injury
What brain injury patterns are associated with severe motor and cognitive disability?
Basal ganglia/thalamic lesions with abN intensity in the PLIC
(Watershed patterns more CI than motor - predictor of language outcome)
What percent of children with moderate basal ganglia/thalamic injury have:
- CP
- CI (IQ<70)
- 60-70% (up to 90% with severe)
2. 35%
What is the most accurate quantitative biomarker for predicting ND outcome after HIE
MRS - deep gray matter lactate and NAA measures
Sensitivity 82%
Specificity 92%
When should infants who were cooled for HIE be imaged?
Days 4-5, after rewarmed
What is the most sensitive modality for neonatal stroke imaging?
MRI - can look at vessels and branches
What vessel branch is most commonly involved in neonatal stroke
left MCA
What does a neonatal stroke look like on MRI acutely?
T1: loss of grey/white matter differentiation
DWI - hyperintense signal = restricted diffusion in the area of infarction
What do you see on MRI at 1-2 mo of age in an infant who had a neonatal stroke?
Tissue loss, cyst formation at site of infarction
What is the best modality for imaging infants with IEM
MRI
What can you see on U/S with IEM?
Cysts
Calcifications
White matter changes
Structural abN
In what IEM disorders is DWI and MRS helpful?
MSUD
nonketotic hyperglycinemia
Creatine deficiency
In traumatic brain injury what do you see with
- U/S
- CT
- MRI
- ICH
- ICH, bone abN, fractures
- Delineates injury, best for parenchymal injury
What imaging modality is the best if there’s suspicion for an underlying fracture
CT
What is the preferred imaging modality in structural brain abN
MRI
What changes do you see on MRI with bilirubin encephalopathy?
Acute: hyperintense signal on T1 in globus pallidus, subthalamic nuclei
Kernicterus: hyperintense signal in T2
When should imaging be done with severe hyperbilirubinemia
Only if there’s encephalopathy
When should an MRI be done in congenital infections
Suspected or proven congenital infections
Established CMV infection
AbN ultrasounds
MRI is the preferred modality for which causes of neonatal encephalopathy
HIE Congenital infection Bilirubin encephalopathy Structural brain abN IEM Neonatal stroke
When is US a useful first imaging modality
Hemorrhage, major structural anomalies, calcification
BUT also ways needs to be confirmed with MRI
When is CT a useful first imaging modality
Urgent situation
MRI is not available
Infant too unstable for MRI
If trauma or suspected skull fracture
