This document summarizes various pediatric white matter diseases seen on imaging. It begins by describing normal myelination patterns in the neonatal brain. It then divides white matter diseases into dysmyelinating, demyelinating, and hypomyelinating categories. Several specific diseases are described in detail, including their characteristic imaging findings. Metachromatic leukodystrophy, Krabbe disease, mucopolysaccharidoses, peroxisomal disorders, adrenoleukodystrophy, Zellweger syndrome, and mitochondrial diseases like MELAS are discussed. Common imaging patterns include abnormal white matter signal, involvement of specific tracts, sparing of U-fibers, and enhancement patterns.

2. Imaging of Pediatric White
Matter Diseases
Dr Tayyaba Niazi
PGR 4
SIMS

3. NORMAL MYELINATION
After normal myelination in utero, myelination of the neonatal brain is far from complete.
It does not reach maturity until 2 years or so. It correlates very closely to developmental milestones .
The progression of myelination is predictable and abides by a few simple general rules; myelination progresses
from:
1. central to peripheral
2. caudal to rostral
3. dorsal to ventral
4. sensory then motor

5. White matter diseases are traditionally divided into two
categories:
• Dysmyelinating diseases
• Demyelinating diseases
• Hypomyelinating diseases
Dysmyelinating diseases - also known as leukodystrophies, result
from an inherited enzyme deficiency that causes abnormal
formation, destruction, or turnover of myelin.
Demyelinating diseases - involve destruction of intrinsically
normal myelin.
Hypomyelinating diseases - the WM may partially myelinate but
never myelinates completely.

6. DYSMYELINATING DISORDERS/
LEUKODYSTROPHIES

7. I
Lysosomal storage disease
Disorder that primarily affect
white matter (Leukodystrophies).

8. TYPES
1. late infantile,
2. juvenile, and
3. adult.
• The most common type is late infantile metachromatic leukodystrophy, in
children between 12 and 18 months of age and is characterized by motor signs of
peripheral neuropathy followed by deterioration in intellect, speech, and
coordination.
• Within 2 years of onset, gait disturbance, quadriplegia, blindness, and decerebrate
posturing may be seen. Death occurs 6 months to 4 years after onset of symptoms

10. Imaging Features:
• At T2-weighted MR imaging, metachromatic leukodystrophy manifests as
symmetric confluent areas of high signal intensity in the periventricular white
matter with sparing of the subcortical U fibers .
• Islands of normal myelin around medullary veins in the WM may produce a
striking "tiger" or "leopard" pattern with linear hypointensities in a sea of
confluent hyperintensity. No enhancement is seen on T1 C+.
• The corpus callosum, internal capsule, and corticospinal tracts are also frequently
involved.
• The cerebellar white matter may appear hyperintense at T2-weighted MR
imaging.

11. Metachromatic leukodystrophy. (a) T2-weighted MR image demonstrates bilateral
confluent areas of high signal intensity in the periventricular white matter. Note
the classic sparing of the sub-cortical U fibers (arrowheads). (b) Contrast material–
enhanced MR image shows lack of enhancement in the demyelinated white
matter, a finding that is characteristic of metachromatic leukodystrophy.

13. Metachromatic leukodystrophy. (a) T2-weighted MR image shows numerous linear tubular
structures with low signal intensity in a radiating (“tigroid”) pattern within the demyelinated
deep white matter. (b) T2-weighted MR image shows a punctate (leopard skin) pat-tern in
the demyelinated centrum semiovale, a finding that suggests sparing of perivascular white
matter. (c) On a contrast-enhanced T1-weighted MR image, the tigroid pattern seen in a
appears as numerous punctate foci of enhancement (arrows) within the demyelinated white
matter, which is unenhanced and has low signal intensity (leopard skin pattern).

14. Metachromatic leukodystrophy with involvement of the corticospinal tract.
T2-weighted MR image shows bilateral high-signal-intensity areas in the periventricular white matter with posterior
predominance. The corpus callosum is also involved (arrows).
T2-weighted MR image obtained at a lower level shows involvement of the descending pyramidal tracts of the medulla
(arrows) and deep cerebellar white matter.

15. Krabbe Disease:
An autosomal recessive disorder caused by a deficiency of
galactocerebroside -galactosidase, an enzyme that degrades
cerebroside, a normal constituent of myelin. .
The diagnosis is made by demonstrating a deficiency of the enzyme in
peripheral blood leukocytes.

16. Clinical presentation:
• Infantile, late infantile, juvenile, and adult forms are recognized.
• The infantile form is the most common and manifests as hyperirritability,
increased muscle tone, fever, and developmental arrest and regression.
• Disease progression is characterized by cognitive decline, myoclonus and
opisthotonus, and nystagmus.
• Typically, Krabbe disease is rapidly progressive and fatal.

17. CT brain:
• CT performed during the initial
stage of the disease may
demonstrate symmetric high-
attenuation foci in the thalami,
caudate nuclei, corona radiata,
posterior limbs of the internal
capsule, and brainstem.

18. Krabbe Disease: Hyperdense thalami and
brain atrophy in frontal region:

19. Krabbe Disease:CT findings in a 4-month-old boy with early-infantile GLD.The series
demonstrates the hyperdensities in the primary myelination zones: brain stem,cerebellum, posterior
limb of the internal capsule, thalamus, and central part of the corona radiata. At this stage the CT
appearance is almost diagnostic, and more characteristic than the MRI findings.

21. Axial T2 weighted images show bilateral parietal, occipital, deep gray matter and
cerebellar white matter hyperintensities with spared subcortical white matter.

22. Mucopolysaccharidosis:
A deficiency of the various lysosomal enzymes involved in the
degradation of glycosaminoglycans.
• Brain imaging is usually performed when hydrocephalus or spinal
cord compression is suspected.
• CT and MR imaging usually reveal delayed myelination, atrophy,
varying degrees of hydrocephalus, and white matter changes.
• As the disease progresses, the lesions become larger and more
diffuse, reflecting the development of infarcts and demyelination.

23. • The major features of
Mucopolysacchroidosis are
• Macrocephaly,
• Enlarged perivascular spaces, A striking
sieve-like cribriform appearance in the
posterior cerebral WM.
• Pachymeningopathy.

24. Mucopolysaccharidosis in a 4-year-old boy with Hurler disease.

25. A patient with MPS II at 21 years of age,
Brain T2-weighted axial MR image demonstrating WM, mainly
found in the retrotrigonal area of the brain, and cribriform
changes in both periventricular and subcortical white matter.
Note also the enlarged ventricles and cortical sulci in the
frontal lobe.

26. Peroxisomal Disorders

28. • The subcortical white matter is relatively spared in the early stage but often becomes involved in the later
stages.
• The affected cerebral white matter typically has three different zones.
 The central or inner zone appears moderately hypointense at T1-weighted MR imaging and
markedly hyperintense at T2-weighted imaging. This zone corresponds to irreversible gliosis and
scarring.
 The intermediate zone represents active inflammation and breakdown in the blood-brain barrier. At
T2-weighted MR imaging, this zone may appear isointense or slightly hypointense and readily
enhances after intravenous administration of contrast material .
 The peripheral or outer zone represents the leading edge of active demyelination; it appears
moderately hyperintense at T2-weighted MR imaging and demonstrates no enhancement .
• Atypical cases with unilateral or predominantly frontal lobe involvement may occur .

30. NECT scans demonstrate
hypodensity in the corpus
callosum splenium and WM
around the atria and occipital
horns of the lateral ventricles.
Calcification in the affected WM
is common.

32. ALD in a 5-year-
old boy

33. ALD with preferential involvement of the internal capsule,descending
pyramidal tract,cerebellar white matter,(a.b)
C. Bilateral enhancement of internal capsule.

34. Atypical ALD
T2-weighted MR image shows
involvement predominantly of the
frontal lobe white matter, genu of the
corpus callosum, and anterior limbs of
the internal capsule (arrows).
Gadolinium-enhanced T1-weighted MR
image shows linear enhancement within
the involved white matter and the
anterior limbs of the internal capsule
(arrows).

35. Zellweger Syndrome
Zellweger syndrome, or cerebrohepatorenal syndrome, is an autosomal recessive disorder caused
by multiple enzyme defects and characterized by liver dysfunction with jaundice, marked
mental retardation, weakness, hypotonia, and craniofacial dysmorphism .
It may lead to death in early childhood. The severity of disease varies and is determined by the
degree of peroxisomal activity.
MR imaging : diffuse demyelination with abnormal gyration that is most severe in the
perisylvian region. The pattern of gyral abnormality is similar to that seen in
polymicrogyria or pachygyria. Subependymal germinolytic cysts are common finding.

36. Zellweger syndrome in a 5-month-old girl
T2-weighted MR image shows extensive areas of diffuse high signal intensity in the white
matter. The gyri are broad, the sulci are shallow, and there is incomplete branching of the
subcortical white matter, findings that suggest a migration anomaly with pachygyria.
On a T1-weighted MR image, the white matter abnormalities demonstrate low signal
intensity

37. Zellweger syndrome spectrum (ZSS)

38. Diseases Caused by Mitochondrial Dysfunction

39. MELAS Syndrome
(mitochondrial encephalopathy with lactic acidosis and stroke-like
episodes)
• Patients with MELAS syndrome usually appear healthy at birth with normal early development, then
exhibit delayed growth, episodic vomiting, seizures, and recurrent cerebral injuries resembling
stroke.
• These stroke like events may give rise to either permanent or reversible deficits.

40. Multiple infarcts involving multiple vascular territories.
Atrophy
MRI
chronic infarcts
• involving multiple vascular territories
• may be either symmetrical or asymmetrical
• parieto-occipital and parieto-temporal (most common)
acute infarcts
• swollen gyri with increased T2 signal
• subcortical white matter involved
• increased signal on DWI (T2 shine through) with little if any change on ADC: thought to
represent vasogenic rather than cytotoxic oedema 3

41. MELAS syndrome in a 10-year-old boy with migrating infarction.

42. Sequential MR images of a female patient with MELAS at ages 8 and 13 years.
A, T2-weighted coronal image during an acute stroke like episode shows parasagittal bilateral
hyperintense lesions (arrows) at the age of 8 years.
B, T2-weighted coronal image 2 months later shows that lesions have almost entirely resolved.
Cerebellar atrophy is evident.
C, T2-weighted axial image 5 years later, during a prolonged seizure, shows a new hyperintense
lesion in the left parietooccipital region (arrow).

43. Leighs Disease
• Leigh disease, or subacute necrotizing encephalomyelopathy, is an inherited, progressive,
neurodegenerative disease of infancy or early childhood with variable course and prognosis .
• Affected infants and children typically present with hypotonia, psychomotor deterioration, ataxia,
ophthalmoplegia, ptosis, dystonia, and swallowing difficulties.
 Typical MR imaging findings include symmetric putaminal involvement, which may be
associated with abnormalities of the caudate nuclei, globus pallidi, thalami, and brainstem and, less
frequently, of the cerebral cortex (Fig 13).
 The cerebral white matter is rarely affected.
 Enhancement may be seen at MR imaging and may correspond to the onset of acute necrosis.

44. • Leighs disease show
hypodensities in bilateral
putamens and globus pallidus.

45. LEIGHS DISEASE

46. LEIGHS DISEASE
Axial FLAIR images show hyperintense lesions in midbrain and
pons posteriorly.

47. Canavan Disease
Canavan disease, or spongiform leukodystrophy, is an autosomal recessive disorder
caused by a deficiency of N-acetylaspartylase, which results in an accumulation of N-
acetylaspartic acid in the urine, plasma, and brain.
It usually manifests in early infancy as hypotonia followed by spasticity, cortical
blindness, and macrocephaly.
Canavan disease is a rapidly progressive illness with a mean survival time of 3 years.
Definite diagnosis usually requires brain biopsy or autopsy.

48. • T1-weighted MR imaging symmetric areas of homogeneous, diffuse low signal intensity ,
whereas T2-weighted , homogeneous high signal intensity throughout the white matter.
• The subcortical U fibers are preferentially affected early in the course of the disease.
• In rapidly progressive cases, the internal and external capsules are involved, and the cerebellar
white matter is usually affected as well.
• As the disease progresses, atrophy becomes conspicuous.

49. Canavan disease in a 6-month-old boy with macrocephaly
T2-weighted MR image shows extensive high-signal-intensity areas throughout the white
matter, resulting in gyral expansion and cortical thinning. Striking demyelination of the
subcortical U fibers is also noted.
T1-weighted MR image shows demyelinated white matter with low signal intensity.

50. CANAVAN DISEASE
Axial T2 weighted image shows high signal in white matter
typically a diffuse bilateral cerebral involvement and sub
cortical U fibres.

51. Alexander Disease
• Alexander disease, or fibrinoid leukodystrophy, is characterized by massive deposition of Rosenthal
fibers in the subependymal, subpial, and perivascular regions (Fig 16b) (37).
• Three clinical subgroups are recognized.
• The infantile subgroup is characterized by early onset of macrocephaly, psychomotor retardation, and
seizure. Death occurs within 2–3 years. Definite diagnosis usually requires brain biopsy or autopsy.
• In the juvenile subgroup, onset 7 and 14 years of age. Progressive bulbar symptoms with spasticity are
common.
• In the adult subgroup, onset between the 2nd and 7th decades. The symptoms and disease course can
be indistinguishable from those of classic multiple sclerosis in the adult subgroup.

52. • Involvement of frontal lobes and subcortical white matter and hyperintensity at T2w image.
• Enhancement near the tips of the frontal horns early in the disease course
.
• These hyperintense areas progress posteriorly to the parietal white matter and internal and external
capsules .
• In the late stages of the disease, cysts may develop in affected regions of the brain.

53. Alexander disease in a 5-year-old boy with macrocephaly

54. Most common leukodystrophies, key points

55. REVISION

57. BILATERAL HYPERDENSE THALAMI ON CT
BILATERAL ABNORMAL SIGNAL INTENSITY IN
THALAMI ON MRI,HYPO ON T2w
Krabbe disease

59. T2w hyperinsities in peri trigonal and occipital
region,with contrast enhancement after injecting
contrast.
Adrenoleukodystrophy

61. Bilateral T1w hypointensity and T2w
hyperintensity of lentiform nuclei
leighs disease

63. T2w hyperintensities in frontal lobes bilateral
Alaxander disease

65. T2w hyperintensities in bilateral periventricular
region with tigroid appearance
Metachromatic leukodystrophy

67. T2w hyperintensity throughout white matter,
macrocephaly.
CANAVAN disease

68. Conclusions
There are many different white matter diseases, each of which has distinctive features.
MR imaging is highly sensitive in determining the presence and assessing the severity
of underlying white matter abnormalities.
Although the findings are often non-specific, systematic analysis of the finer details of
disease involvement may permit a narrower differential diagnosis, which the clinician
can then further refine with knowledge of patient history, clinical testing, and
metabolic analysis.
MR imaging has also been extensively used to monitor the natural progression of
various white matter disorders and the response to therapy.

69. THANK YOU