Radiology of demyelinating diseases

1. Dr. Sunil Kumar Sharma
Senior Resident
Dept. of Neurology
GMC Kota

2. Introduction
 Demyelinating diseases comprise of diseases of central
and peripheral nervous system in which disruption of
myelin is a dominant feature.
 Diseases affecting central nervous system (CNS) myelin
can be classified on the basis of whether a primary
biochemical abnormality of myelin exists(dysmyelinating)
or whether some other process damages the myelin or
oligodendroglial cells (demyelinating).

3. • Cell Body
• Dendrites
• Axons
– Presynaptic
terminals
– Bundles of
axons form
nerves

4. Myelin sheath
 Gray matter primarily contains neurons and their
processes & the white matter is composed
predominantly of myelinated bundles of axons
 The oligodendroglial cell membrane is the source of
the myelin sheath, which is a tightly wrapped,
multilayered membrane which ensheathes axons

5. Myelin sheath
Cholesterol, galactocerebroside,
sphingomyelin, and phospholipids
are the lipids found in fully formed
white matter and account for the
stability and strength . Transmission electron micrograph of
a myelinated axon, myelin sheath,
which is a tightly wrapped,
multilayered membrane

6. Classification of diseases of
myelin

8. Acute disseminated
encephalomyelitis (ADEM)
 Best diagnostic clue: Multifocal WM/basal ganglia
lesions 7-14 days following infection/vaccination
 Location: May involve both brain and spinal cord;
predominantly WM but also gray matter (GM)

9. MRI Findings
 T2WI: T2 abnormalities better seen with FLAIR
FLAIR
 Multifocal punctate to large flocculent FLAIR
hyperintensities
 Bilateral but asymmetric Involve peripheral WM/GM
junction
 Can involve brain stem and posterior fossa
 Do not usually involve callososeptal interface
 Tumefactive, mass-like lesions possible, yet with less
mass effect than expected for size

10. ADEM…
DWI
 Variably restricted diffusion in acute lesions
 Apparent diffusion coefficient (ADC): Increased In
ADEM Due to extracellular water within
demyelination

11. T1 C+
 Punctate, ring, incomplete ring, peripheral
enhancement
 Cranial nerve(s) may enhance
MRS
 N-acetylaspartate (NAA) low within regions of
prolonged T2
 Other metabolites usually normal
Best imaging tool-Contrast-enhanced MRI

15. Acute disseminated
encephalomyelitis.
A: SagittalT2-weighted image
demonstrates high signal
intensity of the majority of
the spinal cord with mild
expansion in the
cervicothoracic region.
B: Axial T2-weighted image
of the cervical cord
demonstrates involvement of
both gray and white matter.

16. Inflammatory Demyelinating
Pseudotumor
 Clinical Features- Demyelinating diseases
occasionally present as solitary, focal, or ill-defined
space-occupying lesions in the brain that closely
mimic a neoplasm both clinically and radiologically.
 These lesions can be found in all age groups but
mostly in the third to fifth decades .
 The clinical features are similar to those of
postinfectious/postvaccinal encephalomyelitis, i.e. an
acute onset of symptoms and dramatic response to
steroids.

17.  In contrast to classic MS, there is no predilection for
the periventricular white matter, optic nerves, or
brainstem.
 If the diagnosis of demyelination is considered, biopsy
can perhaps be delayed and patients can be imaged
after treatment with steroids to look for regression of
MR findings

18. Inflammatory demyelinating
pseudotumor-
Axial FLAIR images demonstrate ill-
defined high signal intensity within
the right frontoparietal white matter
(A) and effacement of adjacent gyri
and extension along the length of the
corticospinal tract,
(B) the posterior limb of the internal
capsule, and
(C) the cerebral peduncle.
Postcontrast axial T1-weighted image
(D) shows ill-defined minimal
enhancement. These findings mimic
the appearance of a large infiltrative
neoplasm.
Biopsy confirmed the presence of
demyelination.

19. Multiple sclerosis (MS)
MR Findings
TlWI
 Acute: Iso-/mildly hypointense
 Chronic: Hypointense center, hyperintense rim
 Variable atrophy; mostly loss of WM
T2WI
 High convexity "sand-like“( < 2 mm diameter) Virchow-
Robin spaces in recent-onset MS
 Hypointense basal ganglia 10-20% chronic MS

20. Multiple sclerosis (MS)…
FLAIR
 Bilateral, asymmetric linear/ovoid FLAIR
hyperintensities
 Perivenular extension; "Dawson finger“ Along path
of deep medullary veins
 Hyperintensities become confluent with severity
DWI
 Acute lesions-Concentric ring pattern on
diffusion-weighted images with hyperintense rim

21. MS…
Tl C+
 Transient enhancement during active
demyelination (> 90% disappear within 6 months)
 Nodular (68%)
 Ring (23%)
 Semilunar, incomplete, "horseshoe-shaped" (9%)

22. MS…
MRS
 NAA (NAA/Cr), Choline (Cho/Cr)
 MRS abnormalities found in NAWM
 Only secondary progressive MS shows NAA in
normal appearing gray matter (NAGM)
 May allow early distinction between relapsing-
remitting & secondary-progressive

23. MR diagnosis of MS requires
 ≥3 discrete lesions ≥5 mm
 Lesions in characteristic location
 MS compatible clinical history
Nuclear Medicine Findings
 PET: Glucose utilization correlates with
NAA in lesions and NAWM
Imaging Recommendations
 Best imaging tool: MRI
 Protocol advice: Contrast-enhanced MR with
sagittal FLAIR

28. Extensive cervical spinal cord lesions with multiple
sclerosis.
A: Sagittal T2-weighted image shows extensive irregular
high signal within the cord substance.
B: Axial T2-weighted image shows the typical peripheral
location of the multiple sclerosis plaque.

29. C: A patient with multiple sclerosis shows an ill-defined lesion on
T2-weighted image extending from the dorsal medulla to C2.
D: Postcontrast T1-weighted image demonstrates minimal
peripheral enhancement.

30. Differential Diagnoses for MS
ADEM
 Viral prodrome, monophasic illness
 Assymetrical
 CC not involved
Autoimmune-mediated Vasculitis
 Enhancing lesions spare callososeptal interface
 "Beaded" angiogram appearance

31. Lyme disease
 Can be identical to MS (skin rash common)
Susac syndrome
 Clinical presentation, course different from MS
 Classic triad of Encephalopathy ,Branch retinal
artery occlusions & Hearing loss.
 Self-limited (2-4 y duration, then stabilizes),
 Monophasic
 Multifocal supratentorial WM lesions
 Always involves CC

32. DDs. Of MS

33. Acute hemorrhagic
leukoencephalitis (Hurst disease)
 Acute hemorrhagic leukoencephalitis (Hurst disease)
is considered a hyperacute or fulminant form of ADEM

 This entity is typically seen in young
 Patients have an abrupt onset of fever, neck stiffness,
and progressive neurologic deficits often leading to
coma and death within 1 to 5 days.

34. Acute hemorrhagic
leukoencephalitis (Hurst disease)…
 reported after viral respiratory infections, sepsis,
ulcerative colitis and asthma, and as a manifestation of
drug toxicity .
 CSF -elevation of IgG and the presence of MBP.
 clinical recovery are reported after the administration
of high-dose steroids

35. Acute hemorrhagic
leukoencephalitis (Hurst disease)
Extensive abnormal signal
involving the
supraventricular white matter
is present, with acute
hemorrhage present as foci of
marked hypointensity within
the white matter lesions.

36. PML
 PML is caused by reactivation of a latent infection by a
papovavirus (JC virus).
 Most cases of PML today occur as a complication of AIDS,
and approx. 5% of all patients with AIDS ultimately
develop PML
 The non-AIDS population typically harbors an underlying
disease affecting immunocompetence, such as leukemia,
lymphoma, sarcoidosis, tuberculosis, or malignancy, or
has received immunosuppressive therapy

37. PML…

38. HIV encephalopathy
 HIV encephalopathy, also known as AIDS dementia
complex, HIV dementia, and hiv-associated dementia
complex is a progressive dementing illness of AIDS.
 Occurs in patients with advanced immunosuppression.
 The most common finding on imaging is atrophy of the
brain.

39. HIV encephalopathy…
 In early stages of the disease, small areas of high signal
intensity are seen on the t2-weighted sequences in the
periventricular white matter that lack mass effect or
edema
 Bilateral symmetric increased signal intensity on the
T2-weighted sequences has been described in the
basal ganglia (caudate and putamen) and thalamus
and may also involve the brainstem

40. Human immunodeficiency
virus encephalopathy in a
patient with acquired
immunodeficiency
syndrome showing diffuse
white matter involvement.
A–D: FLAIR images
progressing inferiorly to
superiorly demonstrate
diffuse white matter signal
abnormality.

41. Human immunodeficiency virus encephalopathy with
characteristic involvement of the basal ganglia.
A: Axial FLAIR image demonstrates bilateral symmetric
increased signal intensity within the basal ganglia and external
capsules.
B: Axial postcontrast T1-weighted image demonstrates no
evidence of enhancement.

42. Neuromyelitis Optica
 Neuromyelitis optica (Devic type) is a syndrome of
acute onset of optic neuritis and transverse myelitis
(LETM) that develop at approximately the same time
 Classically, NMO patients have relapses consisting of
optic neuritis and myelitis
 The target of the NMO antibody is the Aquaporin-4
(AQP4).

44. Central Pontine and Extrapontine
Myelinolysis (Osmotic Demyelination)
 Central pontine myelinolysis describes demyelination
usually isolated to the central pons; however,
extrapontine sites of demyelination are not uncommon.
 It is commonly found in association with alcoholism,
chronic nutritional deficiency, and many other systemic
disorders with electrolyte abnormalities including
chronic pulmonary disease, liver and kidney diseases,
diabetes mellitus, liver transplant, and neoplasia.

45.  The term “osmotic demyelination syndrome” has been
proposed because of the common association with
rapidly corrected hyponatremia.
 The symptoms of central pontine myelinolysis include
spastic quadriparesis, pseudobulbar palsy, changing
levels of consciousness, and coma .
 A significant proportion of patients progress to death,
which may be preceded by a state of pseudocoma
(locked-in syndrome).

46. Central pontine myelinolysis.
A: T2-weighted axial image shows characteristic high signal
intensity within the midpons, with a surrounding rim of
normal-appearing pontine parenchyma and sparing of the
corticospinal tracts.
B: Sagittal T1-weighted image demonstrates a low-signal lesion
within the pons.

48. Marchiafava-Bignami Disease
 Marchiafava-Bignami disease is a rare condition in
which demyelination and necrosis primarily affect the
corpus callosum and sometimes also involve
extracallosal regions.
 It is almost exclusively found in male alcoholics and
was originally described in Italian people who drank
red wine .
 In more recent years, it has been described in poorly
nourished nondrinkers

49. Marchiafava-Bignami Disease…
Sagittal T1-weighted image
(A) demonstrates small
areas of low signal intensity
in the genu, body, and
splenium of the CC

50. Subacute Combined Degeneration
of the Spinal Cord
 Vitamin B12 (cobalamin) deficiency may affect the CNS
or peripheral nervous system but most commonly
involves the spinal cord.
 Subacute combined degeneration (SCD) refers to
vitamin B12 deficiency with demyelination and
vacuolation found in the posterior and lateral columns
of the spinal cord

51. Subacute combined degeneration of the spinal cord
(B12 deficiency).
A: Sagittal T2-weighted image demonstrates a long
segment of high signal intensity within the dorsal aspect
of the cervical spinal cord.
B: Axial T2-weighted image shows high signal intensity
within the dorsal columns.

52. Hypertensive Encephalopathy (Reversible
Posterior Leukoencephalopathy)
 Hypertensive encephalopathy is a clinical entity that it is
important to recognize early because the clinical and
imaging findings are usually reversible.
 Acute elevation of blood pressure (several hours to days
before the onset of symptoms) is the most common
precipitant
 The syndrome can also be seen with renal
decompensation, preeclampsia/eclampsia, fluid retention,
and treatment with immunosuppressive drugs .
 Cyclosporine ,tacrolimus, FK506, L-asparaginase,
cisplatin, and mouse monoclonal antibody (OKT3)

54. Thank You

55. References
 Magnetic Resonance Imaging of the Brain and Spine,
4th ed, 2009, Scott W. Atlas
 Bradley ; neurology in clinical practice 7’th edition
 Osborn Diagnostic Imaging Brain 2004