Cranial Ultrasonography
Cranial ultrasonography is the modality of choice for the initial evaluation of hypoxic-ischemic damage of the central nervous system (CNS) in premature infants. Ultrasonography may be performed in the neonatal intensive care unit (NICU) without the need to transport fragile infants.
The earliest ultrasonographic appearance of periventricular leukomalacia (PVL) is abnormal increased echotexture in the periventricular white matter. This is a nonspecific finding that must be differentiated from the normal periventricular halo and mild periventricular edema that may not result in permanent injury.
The abnormal periventricular echotexture of periventricular leukomalacia usually disappears at 2-3 weeks. Approximately 15% of infants experiencing periventricular leukomalacia demonstrate periventricular cysts first appearing at 2-3 weeks after the initial increased echodensities.
The severity of periventricular leukomalacia is related to the size and distribution of these cysts. Initial cranial ultrasonographic findings may be normal in patients who go on to develop clinical and delayed imaging findings of periventricular leukomalacia. Examples of cranial ultrasonography in periventricular leukomalacia are shown in the images below.
Pediatric Periventricular Leukomalacia. Cranial ultrasound, coronal view, in a 1-week-old premature infant. The periventricular echotexture is abnormally increased (greater than or equal to that of the choroid plexus), which is consistent with the early changes of periventricular leukomalacia (PVL). Courtesy of Matthew Omojola, MD.
Pediatric Periventricular Leukomalacia. Cranial ultrasound, coronal view, in a 1-week-old premature infant without periventricular leukomalacia (PVL). The periventricular echotexture is normal. Compare this image with the previous image. Courtesy of Matthew Omojola, MD.
Pediatric Periventricular Leukomalacia. Cranial ultrasound, coronal view, in a 3-week-old premature infant. Multiple bilateral periventricular cysts are typical of this stage of periventricular leukomalacia (PVL). Courtesy of Matthew Omojola, MD.
Pediatric Periventricular Leukomalacia. Cranial ultrasound, sagittal view, in a 3-week-old premature infant. Multiple periventricular cysts are typical of this stage of periventricular leukomalacia (PVL). Courtesy of Matthew Omojola, MD.
The strongest predictor for mental delay on Bayley score at age 2 years for preterm infants born with a birth weight up to 1.25 kg appears to be a ventricular-brain ratio above 0.35 on term-equivalent cranial ultrasonography. [33]
Computed Tomography Scanning
Computed tomography (CT) scanning is not a first-line modality in evaluating these fragile premature infants in the first weeks of life. CT scanning may be helpful to better evaluate the extent and severity of periventricular leukomalacia (PVL).
CT findings include ventriculomegaly involving the lateral ventricles with irregular margins of the ventricles and loss of deep white matter. Examples of CT scans in periventricular leukomalacia are shown in the images below.
Pediatric Periventricular Leukomalacia. Cranial computed tomography (CT) scan, axial image, in a 5-week-old premature infant with periventricular leukomalacia (PVL). The ventricular margins are irregular, which is consistent with incorporation of the periventricular cysts of PVL. Mild ventriculomegaly and loss of the periventricular white matter is observed. Courtesy of Matthew Omojola, MD.
Pediatric Periventricular Leukomalacia. Cranial computed tomography (CT) scan, axial image, in a 14-month-old child with periventricular leukomalacia (PVL). Ventriculomegaly is limited to the lateral ventricles secondary to diffuse loss of periventricular white matter. Courtesy of Matthew Omojola, MD.
Magnetic Resonance Imaging
As with computed tomography (CT) scanning, magnetic resonance imaging (MRI) does not play a major role in the early evaluation of periventricular leukomalacia (PVL). MRI is most helpful in detecting infants with non-cystic periventricular leukomalacia or evaluating infants who develop clinical signs suggestive of periventricular leukomalacia. [34]
MRI demonstrates the loss of white matter, abnormal signal intensity of the deep white matter, and ventriculomegaly; it also reveals thinning of the posterior body and splenium of the corpus callosum in severe cases of periventricular leukomalacia.
In a study of MRIs at term-equivalent age from 3 cohorts of 325 very preterm infants, Kidokoro et al found 33% (n=107) had some grade of brain injury (eg, periventricular leukomalacia, intraventricular/cerebellar hemorrhage) and 10% (n=33) had severe brain injury. [35] The investigators noted severe brain injury and impaired growth patterns were independently associated with perinatal risk factors and delayed cognitive development. [35]
Lu et al found that patients with periventricular leukomalacia can be differentiated from control subjects by assessing the dark stripe in the peritrigonal (PT) white matter on apparent diffusion coefficient (ADC) maps. [36] They reviewed the magnetic resonance studies of 27 neonates and young children with periventricular leukomalacia and 67 control subjects. On the ADC map, a complete PT dark stripe was present in 100% of control subjects but only in 14.8% of patients with periventricular leukomalacia, with a sensitivity of 0.85, specificity of 1.0, and accuracy of 0.96. [36]
Volumetric MRI scanning is also helpful in determining the extent of injury to the descending corticospinal tracts.
A relationship between the degree of injury to the descending corticospinal tracts as assessed by MRI and the severity of diplegia has been reported.
Examples of MRI in periventricular leukomalacia are shown in the images below.
Pediatric Periventricular Leukomalacia. Cranial magnetic resonance image (MRI), T1-weighted axial image, in an 18-month-old with periventricular leukomalacia (PVL). The lateral ventricles are enlarged without hydrocephalus. The periventricular white matter is diminished. Courtesy of Matthew Omojola, MD.
Pediatric Periventricular Leukomalacia. Cranial magnetic resonance image (MRI), T2-weighted axial image, in an 18-month-old with periventricular leukomalacia (PVL). Again, enlarged ventricles and loss of white matter are demonstrated. Also noted is the abnormal increased signal in the periventricular regions on this T2-weighted image. Courtesy of Matthew Omojola, MD.
Pediatric Periventricular Leukomalacia. Cranial magnetic resonance image (MRI), sagittal T1-weighted image in the midline, in an 18-month-old child with periventricular leukomalacia (PVL). Hypoplasia of the corpus callosum is present and is most evident, involving the body. Courtesy of Matthew Omojola, MD.
Other Studies
Obtain electroencephalography (EEG) studies in preterm infants for early detection of periventricular leukomalacia (PVL). EEG biomarkers are associated with this injury in preterm infants. [37] Changes in hypoxic-ischemic encephalopathy and EEG wave patterns may change over time and indicate the severity of the brain injury. [1] EEG abnormalities may be apparent before anomalies seen on ultrasonography.
Spectral-domain optical coherence tomography (SD-OCT) shows promise in the evaluation of prematurity on early optic nerve development and of central nervous system development and anomalies. [38]
On histologic examination, periventricular leukomalacia lesions demonstrate widespread loss of oligodendrocytes and an increase in astrocytes.
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Pediatric Periventricular Leukomalacia. Cranial ultrasound, coronal view, in a 1-week-old premature infant. The periventricular echotexture is abnormally increased (greater than or equal to that of the choroid plexus), which is consistent with the early changes of periventricular leukomalacia (PVL). Courtesy of Matthew Omojola, MD.
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Pediatric Periventricular Leukomalacia. Cranial ultrasound, coronal view, in a 1-week-old premature infant without periventricular leukomalacia (PVL). The periventricular echotexture is normal. Compare this image with the previous image. Courtesy of Matthew Omojola, MD.
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Pediatric Periventricular Leukomalacia. Cranial ultrasound, coronal view, in a 3-week-old premature infant. Multiple bilateral periventricular cysts are typical of this stage of periventricular leukomalacia (PVL). Courtesy of Matthew Omojola, MD.
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Pediatric Periventricular Leukomalacia. Cranial ultrasound, sagittal view, in a 3-week-old premature infant. Multiple periventricular cysts are typical of this stage of periventricular leukomalacia (PVL). Courtesy of Matthew Omojola, MD.
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Pediatric Periventricular Leukomalacia. Cranial computed tomography (CT) scan, axial image, in a 5-week-old premature infant with periventricular leukomalacia (PVL). The ventricular margins are irregular, which is consistent with incorporation of the periventricular cysts of PVL. Mild ventriculomegaly and loss of the periventricular white matter is observed. Courtesy of Matthew Omojola, MD.
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Pediatric Periventricular Leukomalacia. Cranial computed tomography (CT) scan, axial image, in a 14-month-old child with periventricular leukomalacia (PVL). Ventriculomegaly is limited to the lateral ventricles secondary to diffuse loss of periventricular white matter. Courtesy of Matthew Omojola, MD.
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Pediatric Periventricular Leukomalacia. Cranial magnetic resonance image (MRI), T1-weighted axial image, in an 18-month-old with periventricular leukomalacia (PVL). The lateral ventricles are enlarged without hydrocephalus. The periventricular white matter is diminished. Courtesy of Matthew Omojola, MD.
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Pediatric Periventricular Leukomalacia. Cranial magnetic resonance image (MRI), T2-weighted axial image, in an 18-month-old with periventricular leukomalacia (PVL). Again, enlarged ventricles and loss of white matter are demonstrated. Also noted is the abnormal increased signal in the periventricular regions on this T2-weighted image. Courtesy of Matthew Omojola, MD.
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Pediatric Periventricular Leukomalacia. Cranial magnetic resonance image (MRI), sagittal T1-weighted image in the midline, in an 18-month-old child with periventricular leukomalacia (PVL). Hypoplasia of the corpus callosum is present and is most evident, involving the body. Courtesy of Matthew Omojola, MD.
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Pediatric Periventricular Leukomalacia. This image depicts cerebral white matter abnormalities in preterm infants found on neuropathological (autopsied) specimens correlating with neuroradiological findings on magnetic resonance images (MRIs) and outcomes. (Data extracted from references 2 Volpe, Pediatr Neurol, 2017], 9 [Volpe et al, Int J Dev Neurosci, 2011], 30 [Guo et al, Neurology, 2017], and 62 [Wagenaar et al, J Pediatr, 2017].)
