Download contribution of mri in serious forms of acute disseminated

CONTRIBUTION OF MRI IN SERIOUS FORMS OF ACUTE
DISSEMINATED ENCEPHALOMYELITIS AND POST
INFECTIOUS HERPES ENCEPHALITIS
M.OMRI, W.HIZEM-HARZALLAH, Z.ABOUZARIFA,
R.SALEM, M.A.JELLALI, A.ZRIG, W.MNARI,
M.MAATOUK, M.GOLLI
Radiology service, Fattouma Bourguiba’s Hospital, Rue 1er
juin, 5004 Monastir, Tunisia
NR29
INTRODUCTION:
• Post-infectious and inflammatory encephalomyelitis are broadly
represented by the syndrome acute disseminated
encephalomyelitis (ADEM).
• ADEM is an inflammatory demyelinating disorder of the central
nervous system that is usually monophasic,which principally
affects brain and spinal cord .
• ADEM is predominantly, though by no means exclusively, a
disease of children and in particular infants. Historically it includes
post infectious encephalomyelitis and post-vaccination
encephalomyelitis.
• It usually follows an infection or vaccination. The disease is
characterised by multifocal white matter lesions on neuroimaging.
• It typically follows a minor infection with a latency period of 2—30
days and is thought to be immune-mediated.
• ADEM is clinically characterized by the acute onset of focal
neurological signs and encephalopathy. Patients can require
intensive care unit admission because of encephalopathy, coma,
seizures or tetraplegia.
• Cerebrospinal fluid analysis usually shows lymphocytic pleocytosis
but, unlike viral or bacterial encephalitis, no evidence of direct
CNSinfection is found.
• There are no biologic markers of the disease and cerebral
magnetic resonance imaging is essential to ADEM diagnosis,
detecting diffuse or multifocal asymmetrical lesions throughout the
white matter on T2- and FLAIR-weighted sequences.
OBJECTIVS:
• Show the contribution of MRI in the
positive diagnosis in acute disseminated
encephalomyelitis (ADEM) in its severe
form and post infectious herpes encephalitis
and also specify his interest prognosis and
clinical correlation radio.
Materials and Methods
• Retrospective analysis of 9 clinical cases( 6 girls and
3 boys) of ADEM (5 cases) and post infectious
herpes encephalitis (4 cases) explored by
conventional MRI and diffusion mapping with CDA.
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•
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Average age: 9 months and 12 years
Recent infection (n = 6).
recent vaccination (n =3 ).
Reason for hospitalization:
- fever (n = 7);
- seizures (n = 5);
-behavioral disorders (n = 4)
• Physical signs:
-impaired consciousness (n = 8);
-meningeal syndrome (n = 5);
-motor deficit (n = 3);
-gait disturbance (n = 2);
-achievement of cranial nerves (n = 4)
• PL (n = 8):
- normal formula (n = 1);
- and lymphocytic meningitis (n = 7)
• Initial brain imaging:
- CT (n = 4);
- MRI (n = 9).
• Additional spinal MRI (n = 3).
• Imaging control in 5 patients:
-MRI (n = 5)
Results:
• Objectified anomalies in all cases were:
• Hyperintensity T2 of white matter brain:
-bilateral and asymmetric (3 cases).
-diffuse (2 cases).
-unilateral (3cases).
• Hyperintensity T2 of profound gray matter (1 case).
• Infectious vasculitis associated with vasoplegia blood
was found in one case.
• Diffusion was restricted with decreased ADC in 4
cases.
• The restriction of diffusion was associated with a
severe clinical picture.
• ADEM lesions are large, multiple, and asymmetric
(5cas).
• Severe and extensive T2 lesions (2cas) contrast
with a relatively small mass effect. The distribution
of lesions involves the subcortical and central
white matter and cortical graye white junction of
both cerebral hemispheres and infratentorial areas.
• A pattern of diffuse demyelination is seen in one
severe case with large demyelinating lesions of the
white matter extending to the contralateral
hemisphere.
A two-years-old previously healthy girl who developed
postinfectious focal encephalitis. MRI findings:
• fluid-attenuated inversion recovery (FLAIR) sequences show
extensive area of increased signal in left hemisphere and right
basal ganglia.
• HSE. T2 weighted MRI showing extensive area of
increased signal in left hemisphere and right basal ganglia
• Diffusion-weighted MRI (DWI) show a
restrection of diffusion.
• T1 with G shows cortical enhancement.
A seven-years-old previously healthy girl who developed
post infectious focal encephalitis . control MRI findings.
• HSE. T2 weighted MRI showing an increased signal in basal ganglia
• fluid-attenuated inversion recovery (FLAIR) sequences show an
increased signal in basal ganglia.
• Diffusion est discreetly restrected.
Discussion:
Acute disseminated encephalomyelitis:
• Post-infectious encephalomyelitis is associated with an
antecedent or concomitant infection, usually viral. Most
notoriously, measles virus infection is followed by ADEM in
approximately 1 in 1000 cases.
• It is greatly reduced in incidence following the introduction of
widespread measles vaccination, but still occurs. Non-specific or
unidentified viral illnesses can also antecede ADEM, and this lack
of a specific infectious agent should not preclude the diagnosis.
• There are some variations in the ADEM phenotype dependent
upon the antecedent illness. Measles associated ADEM tends to
produce a more clinically severe phenotype while cerebellar
ataxia .
• ADEM can be distinguished from acute viral encephalitis because
the disease is not the result of primary tissue invasion by an
infectious organism. It is thought to be immune-mediated and is
characterized neuropathologically by perivenular inflammation
and demyelination.
Neuroimaging:
• Cerebral computed tomography scans performed at admission
show abnormalities only in 30% of patients, essentially
supratentorial readily visible diffuse or large focal hypodensities
of the cerebral white matter.
• Demyelinating lesions of ADEM are better visualised by MRI.
These demyelinating lesions of ADEM usually exhibit no mass
effect and can be seen scattered throughout the white matter of
the posterior fossa and cerebral hemispheres
• Involvement of the cerebellum and brainstem is more common in
children. Characteristic lesions seen on MRI appear as patchy
areas of increased signal intensity on conventional T2-weighted
images and on fluid attenuated inversion recovery sequence
(FLAIR).
• Few MRI lesions may enhance after gadolinium administration.
Extensive perifocal oedema may be seen.
• Though white matter involvement predominates grey matter can
alsobe affected, particularly basal ganglion, thalami, and
brainstem. Tumour-like lesions have also been reported in a few
cases.
• MRI lesions are identified on morphological T2-weighted and fluidattenuated inversion recovery (FLAIR) sequences.
• Although no specific MRI criteria have been identified. MRI lesion
patterns are generally recognized, but in all cases lesions are
multifocal and involve mainly the supratentorial white matter:
-multifocal lesions of less than 5 cm.
-confluent multifocal lesions of more than 5 cm.
- multifocal lesions involving basal ganglia.
• Although patchy areas of increased signal intensity are
stated to involve 50% or more of total white matter in
children.
• In order to qualify as ADEM, lesions on MRI should be of
the same age and no new lesion should appear on central
nervous system imaging studies after the initial clinical
attack.
• The corpus callosum is usually not involved in ADEM;
infrequently its involvement has been reported, suggesting
extensive lesion load. Corpus callosum involvement is
more characteristic of multiple sclerosis.
• Thalamic involvement may be seen in 40% patients of ADEM,
making this finding a potentially useful discriminator.
• MRI changes usually appear early in the course of the disease.
• Although ADEM is typically a disseminated process in the central
nervous system, often with impaired sensorium, a few cases are
dominated by spinal pathology .
DIFFERENTIAL DIAGNOSIS :
• Distinction between infectious and post-infectious encephalitis can
be difficult and all frequent causes of infectious encephalitis must
be excluded before concluding to an acute form of post-infectious
inflammatory CNS disorder.
• The diagnosis is considered straightforward when ADEM occurs
after an exanthem or immunisation. A clear cut latent period
between systemic symptoms and neurological illness favours
ADEM along with the typical pattern of diffuse and multifocal
involvement of both the central nervous system and peripheral
nervous system and the characteristic MRI appearance.
• The most important issue associated with the diagnosis of ADEM is
can this disorder be diagnosed with certainty and differentiated
from the initial manifestation of multiple sclerosis.
CONCLUSION:
• ADEM is a monophasic inflammatory disease affecting the
central nervous system, which usually follows an infection or
vaccination.
• Distinction between infectious and post-infectious encephalitis can be difficult and all frequent causes of infectious
encephalitis must be excluded before concluding to an
acute form of post-infectious inflammatory CNS disorder.
• Diffuse and focal CNS signs and peripheral nervous system
involvement may be present simultaneously at physical
examination. Brain and spinal cord MRI should be
systematically performed at the initial phase of the disease to
look for evidence of multifocal acute inflammation and
demyelination.