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Dr. Sunil Kumar Sharma
Dept. of Neurology
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).
• Cell Body
– Bundles of
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
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,
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)
T2WI: T2 abnormalities better seen with FLAIR
Multifocal punctate to large flocculent FLAIR
Bilateral but asymmetric Involve peripheral WM/GM
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
Variably restricted diffusion in acute lesions
Apparent diffusion coefficient (ADC): Increased In
ADEM Due to extracellular water within
Punctate, ring, incomplete ring, peripheral
Cranial nerve(s) may enhance
N-acetylaspartate (NAA) low within regions of
Other metabolites usually normal
Best imaging tool-Contrast-enhanced MRI
A: SagittalT2-weighted image
demonstrates high signal
intensity of the majority of
the spinal cord with mild
expansion in the
B: Axial T2-weighted image
of the cervical cord
demonstrates involvement of
both gray and white matter.
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
In contrast to classic MS, there is no predilection for
the periventricular white matter, optic nerves, or
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
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
(B) the posterior limb of the internal
(C) the cerebral peduncle.
Postcontrast axial T1-weighted image
(D) shows ill-defined minimal
enhancement. These findings mimic
the appearance of a large infiltrative
Biopsy confirmed the presence of
Multiple sclerosis (MS)
Acute: Iso-/mildly hypointense
Chronic: Hypointense center, hyperintense rim
Variable atrophy; mostly loss of WM
High convexity "sand-like“( < 2 mm diameter) Virchow-
Robin spaces in recent-onset MS
Hypointense basal ganglia 10-20% chronic MS
Multiple sclerosis (MS)…
Bilateral, asymmetric linear/ovoid FLAIR
Perivenular extension; "Dawson finger“ Along path
of deep medullary veins
Hyperintensities become confluent with severity
Acute lesions-Concentric ring pattern on
diffusion-weighted images with hyperintense rim
Transient enhancement during active
demyelination (> 90% disappear within 6 months)
Semilunar, incomplete, "horseshoe-shaped" (9%)
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
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
Best imaging tool: MRI
Protocol advice: Contrast-enhanced MR with
Extensive cervical spinal cord lesions with multiple
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.
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
Differential Diagnoses for MS
Viral prodrome, monophasic illness
CC not involved
Enhancing lesions spare callososeptal interface
"Beaded" angiogram appearance
Can be identical to MS (skin rash common)
Clinical presentation, course different from MS
Classic triad of Encephalopathy ,Branch retinal
artery occlusions & Hearing loss.
Self-limited (2-4 y duration, then stabilizes),
Multifocal supratentorial WM lesions
Always involves CC
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.
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
leukoencephalitis (Hurst disease)
Extensive abnormal signal
supraventricular white matter
is present, with acute
hemorrhage present as foci of
marked hypointensity within
the white matter lesions.
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
The non-AIDS population typically harbors an underlying
disease affecting immunocompetence, such as leukemia,
lymphoma, sarcoidosis, tuberculosis, or malignancy, or
has received immunosuppressive therapy
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
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
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
virus encephalopathy in a
patient with acquired
syndrome showing diffuse
white matter involvement.
A–D: FLAIR images
progressing inferiorly to
diffuse white matter signal
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
B: Axial postcontrast T1-weighted image demonstrates no
evidence of enhancement.
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
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.
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
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
B: Sagittal T1-weighted image demonstrates a low-signal lesion
within the pons.
Marchiafava-Bignami disease is a rare condition in
which demyelination and necrosis primarily affect the
corpus callosum and sometimes also involve
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
Sagittal T1-weighted image
(A) demonstrates small
areas of low signal intensity
in the genu, body, and
splenium of the CC
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
Subacute combined degeneration of the spinal cord
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.
Hypertensive Encephalopathy (Reversible
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
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)
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
Notas del editor
Cell Body Contains the nucleus Dendrites Receptive regions; transmit impulse to cell body Short, often highly branched May be modified to form receptors Axons Transmit impulses away from cell body Axon hillock; trigger zone Where action potentials first develop Presynaptic terminals (terminal boutons) Contain neurotransmitter substance (NT) Release of NT stimulates impulse in next neuron Bundles of axons form nerves