Imaging of viral
encephalitis
Osama A. Ragab
Assist,Lec of Neurology
introduction
 The word “virus” is derived from the Latin word for
poison.
 Viruses are infectious, obligate intracellula...
Virus structure
Nucleic Acid
Spike
Projections
Protein
Capsid
Lipid Envelope
Virion
Associated
Polymerase
Virus taxonomy
 Within the ICTV( the International Committee for
Taxonomy of Viruses) system ,the two major
taxonomic div...
HERPESVIRIDAE
HEPADNAVIRIDAE
ENVELOPED
PAPILLOMAVIRIDAE
POLYOMAVIRIDAE
(formerly grouped together as the
PAPOVAVIRIDAE)
CI...
FLAVIVIRIDAE
TOGAVIRIDAE
RETROVIRIDAE
ICOSAHEDRAL
CORONAVIRIDAE
HELICAL
ENVELOPED
ICOSAHEDRAL
PICORNAVIRIDAE
CALICIVIRIDAE...
Geographic distribution of selected viruses
causing central nervous system infection.
Neurotopic virus
HERPESVIRUSES
HERPESVIRUSES
 Family Herpesviridae includes over 80 viruses
distributed among three subfamilies: Alpha, Beta and
Gamma.
...
 These viruses are neurotropic and establish latent
infections in ganglionic neurons during primary
infection, subsequent...
 Pathologically, HSV-1 results in a necrotizing
infection involving the :
 inferomedial aspect of the temporal lobes.
 ...
 CT is often normal, although non-specific
hypoattenuating lesions in the temporal and/or
frontal lobes with or without e...
 51-year-old diabetic woman with fever and confusion. (a) Unenhanced axial
CT scan shows no significant changes in the le...
 Axial fluid attenuated inversion recovery image
(A) demonstrates a region of increased signal
intensity in the right tem...
Herpes simplex virus 1 (HSV-1)
Axial T1 Image demonstrate curvilinear regions of high T1 signal intensity
within the right...
DWI demonstrates
regions of patchy
restricted diffusion and
may be more sensitive
than T2-weighted or
FLAIR imaging in
dep...
 DWI classic herpes encephalites note abnormal
hyperintense signal abnormallity in bilateal mesial
temporal corex .
Herpe...
 classic herpes encephalites note
abnormal hyperintense signal
abnormallity in bilateal mesial temporal
corex & cingulate...
 T1 with contrast
 HSV-2 may result in severe neonatal encephalitis,
with transmission most commonly occurring through
an infected birth ca...
 With disease progression, decreased T2 signal
intensity within the cortex may develop
corresponding to the presence of f...
 Cortical blurring and gyral/leptomeningeal enhancement in neonatal HSV-2
encephalitis in different patients.
 A Axial T...
 a Axial FLAIR image is normal in this 13-day
old patient presenting with signs of sepsis and
culture negative meningitis...
 Axial DW image demonstrates
restricted diffusion in the left caudate
nucleus head (arrowhead) and the right
lentiform nu...
 Axial DW image in another patient
demonstrates restricted diffusion
in the pons (arrow) and deep
cerebellar hemispheres
...
 Meningoencephalitis with MRI demonstrating diffuse,
multifocal areas of high T2 signal intensity within the
cerebral cor...
 The spread of VZV from blood vessels to the
ependymal cells lining the ventricles may result in
ventriculitis, resulting...
Varicella-zoster virus encephalitis with multifocal vasculopathy. Axial fluid
attenuated inversion recovery (FLAIR) (A) an...
 Magnetic resonance image of a 6-month-old boy. (a, b) Axial
T2 gradient echo sequence: blood in the ventricles and
hydro...
 Magnetic resonance image of a 35-year-old man. (a-c) Cranial magnetic resonance image, FLAIR
sequence showing punctiform...
 Magnetic resonance
image of a 20-year-old
man. Narrowing of the Ml
segment of the middle
cerebral artery.
Epstein-Barr virus (EBV)
 EBV infection of the nervous system is uncommon
but may result in meninigitis, encephalitis, my...
 case reports of progression to hemorrhagic
encephalitis have been published and should be a
consideration with worsening...
Epstein–Barr virus. Axial T2-weighted image (A) imaging demonstrates
abnormal increased signal in the right temporal lobe....
 Anon-contrast CT scan (C) performed the same day
demonstrates partial hemorrhagic conversion of the
lesion with adjacent...
 Initial MR imaging of the patient. T1-weighted image does not reveal any
abnormality (A). T2-weighted image depicts high...
 Brain MRI scan findings in a 12-year-old boy with Epstein–Barr virus
encephalitis. The scans were performed 1 day before...
 CMV infection of the nervous system is most often seen
with immunocompromised patients .
 CMV is the leading cause of c...
 MRI demonstrates non-specific increased T2 and
decreased T1 signal abnormalities in the white
matter which may have a pa...
 CT imaging in infants with congenital CMV infection
classically shows intracranial calcifications in a
periventricular d...
In uterocytomegalovirus (CMV) infection. Coronal true inversion recovery image
demonstrates thickened and disordered corte...
In utero cytomegalovirus (CMV) infection. Axial non-contrast computed
tomography scan of the head demonstrates massive hyd...
In uterocytomegalovirus (CMV) infection. Coronal T2-weighted image
demonstrates thickened and disordered cortex in the rig...
 Axial (a) T1 and (b) T2 weighted MRI show mild ventricular dilatation and multiple tiny nodular T2 high-signal intensity...
 Reactivation of latent HHV-6 infection in
immunocompromised patients, may result in an
encephalitis, leptomeningitis, or...
Herpes simplex virus 6 (HSV-6)
Human herpesvirus-6 (HHV) infection. Axial fluid attenuated inversion recovery
image of the...
Flaviviruses
 Humans typically acquire infection through the bite of
an infected mosquito or tick .
 The major human pathogens among ...
 JEV primarily affects developing neurons in thalamus,
hippocampus, and midbrain, while anterior horn cells of
the spinal...
St. Louis encephalitis (SLE)
 SLE is transmitted through a mosquito-borne virus
and has resulted in several epidemics in ...
 St. Louis encephalitis. Axial T2-weighted images demonstrate symmetric
increased signal intensity involving the insular ...
West Nile encephalitis
 West Nile encephalitis is an emerging infection with
a rapid increase in incidence and geographic...
 West Nile encephalitis. Axial fluid attenuated inversion recovery
images (A, B) demonstrate increased signal in the thal...
Japanese encephalitis
 Japanese encephalitis (JE) is the most frequent
global cause of mosquito-borne encephalitis and is...
Japanese encephalitis
Japanese encephalitis. Axial fluid attenuated inversion recovery images in
two different patients wi...
Bunyaviridae
 Between the period of October 2003 and April 2005
an epidemic of RVF encephalitis appeared in the
region of Khafer Al-Sh...
 MRI of the brain demonstrated the following: patchy
areas of edema targeting the cortical and subcortical
deep white mat...
 C.T brain scan demonstrate gray matter affection with
diffuse white matter affection & mainly in the region of
basal gan...
 MRI of the brain T2 weighted images demonstrate evidence of
gray
matter affection with diffuse white matter edema
Arenaviruses
Arenaviruses
 Lymphocytic choriomeningitis virus can cause
aseptic meningitis (rarely fatal), hydrocephalus, and
more sev...
lymphocytic choriomeningitis virus (LCMV)
 prenatal disease may result in devastating
neuroteratogenic effects.
 the mos...
 2 children with congenital LCMV infection (B, C). (B) The most common abnormalities
in congenital LCMV infection include...
 (B) In congenital LCMV infection, the virus can impair
cerebellar growth and lead to cerebellar hypoplasia
(arrow).
Retroviruses
Retroviruses
 The major human retroviruses include human T
lymphotropic viruses 1 and 2 and HIV-1 and -2.
 Both HTLV-1 a...
Retroviruses
 HIV-associated neurologic disorders include
neurocognitive disorders and peripheral
neuropathies as well as...
 Early changes of HIV encephalitis manifest as
multifocal subcentimeter white-matter lesions
appearing bright on T2-weigh...
 Another chronic feature of HIV infection is
progressive cerebral atrophy, which is most
prominent centrally, resulting i...
Polyomaviruses
 The first human members of family Polyomaviridae, JC
virus (JCV) and BK virus (BKV) (both of genus
Orthopolyomavirus).
...
Progressive multifocal leukoencephalopathy
 PML is most commonly seen in the setting of
underlying HIV-1 infection, it ma...
 Early on, the lesions may be small but then progress
to form larger areas of involvement, often with a
scalloped border....
 This is an MRI of the brain of a PML survivor (PML-S).
On the left is a fluid attenuated inverse recovery (FLAIR)
image,...
 This is an MRI of the brain of a PML- survivor. On the left, FLAIR image
shows a large hyperintense lesion in the white ...
Paramyxoviruses
Paramyxoviruses
 Measles virus infections can lead to three neurologic
diseases.
 Acute disseminated encephalomyelitis t...
Subacute sclerosing panencephalitis (SSPE)
 SSPE is a chronic and progressive encephalitis
caused by a persistent infecti...
subacute sclerosing panencephalitis (SSPE). Axial T2-weighted image
demonstrates symmetric regions of increased signal int...
Rhabdoviruses
Rhabdoviruses
 Rabies virus transmitted through skin by animal bites
the virus is transmitted directly to peripheral neur...
Rabies encephalitis
 MR features of rabies encephalitis describe ill-
defined mild areas of T2 hyperintensity in the
brai...
Picornaviruses
 that include viruses of humans are Enterovirus,
Hepatovirus, and Parechovirus. The human enteroviruses
include polioviru...
Enteroviral encephalitis
 EV71 characteristic MR findings are hyperintensity in
the posterior portions of the medulla and...
Enteroviral encephalitis. Axial T2-weighted image demonstrates
symmetric regions of increased signal intensity involving t...
Orthomyxoviruse
s
Orthomyxoviruses
 Influenza viruses A, B, and C are well known as the
causes of influenza.
 Neurologic manifestations of...
 Influenza A. Axial fluid attenuated inversion recovery (A)andT1postcontrastimage(B)
demonstrate bilateral asymmetric non...
imaging of viral encephalitis
imaging of viral encephalitis
Upcoming SlideShare
Loading in …5
×

imaging of viral encephalitis

5,745 views

Published on

neuroimaging of viral encephalitis

Published in: Health & Medicine
  • Be the first to comment

imaging of viral encephalitis

  1. 1. Imaging of viral encephalitis Osama A. Ragab Assist,Lec of Neurology
  2. 2. introduction  The word “virus” is derived from the Latin word for poison.  Viruses are infectious, obligate intracellular parasites whose genomes consist of either DNA or RNA.  A minimal virus consists of a genome plus a proteinaceous coat, known as a capsid.  Enveloped viruses, are enclosed by a host cell- derived lipid bilayer studded with virus-specified glycoproteins.
  3. 3. Virus structure Nucleic Acid Spike Projections Protein Capsid Lipid Envelope Virion Associated Polymerase
  4. 4. Virus taxonomy  Within the ICTV( the International Committee for Taxonomy of Viruses) system ,the two major taxonomic divisions are the viruses with RNA genomes and those with DNA genomes.  Subsequent taxonomic levels are based on the size and structure of the capsid and then the nature of the genome (single-stranded or double-stranded, linear or circular, segmented or non-segmented).
  5. 5. HERPESVIRIDAE HEPADNAVIRIDAE ENVELOPED PAPILLOMAVIRIDAE POLYOMAVIRIDAE (formerly grouped together as the PAPOVAVIRIDAE) CIRCULAR ADENOVIRIDAE LINEAR NON-ENVELOPED DOUBLE STRANDED PARVOVIRIDAE SINGLE STRANDED NON-ENVELOPED POXVIRIDAE COMPLEX ENVELOPED DNA VIRUSES Virus taxonomy
  6. 6. FLAVIVIRIDAE TOGAVIRIDAE RETROVIRIDAE ICOSAHEDRAL CORONAVIRIDAE HELICAL ENVELOPED ICOSAHEDRAL PICORNAVIRIDAE CALICIVIRIDAE ASTROVIRIDAE NONENVELOPED SINGLE STRANDED positive sense BUNYAVIRIDAE ARENAVIRIDAE ORTHOMYXOVIRIDAE PARAMYXOVIRIDAE RHABDOVIRIDAE FILOVIRIDAE SINGLE STRANDED negative sense REOVIRIDAE DOUBLE STRANDED RNA VIRUSES ENVELOPED HELICAL ICOSAHEDRAL NONENVELOPED Virus taxonomy
  7. 7. Geographic distribution of selected viruses causing central nervous system infection.
  8. 8. Neurotopic virus
  9. 9. HERPESVIRUSES
  10. 10. HERPESVIRUSES  Family Herpesviridae includes over 80 viruses distributed among three subfamilies: Alpha, Beta and Gamma.  Human viruses are members of the Alpha herpesvirinae: HSV-1 and HSV-2 and varicella- voster virus .  Human Beta herpesvirinae include human cytomegalovirus human herpesviruses 6A and 6B and human herpesviruses 7.  Human Gamma herpesvirinae are hosts to Epstein– Barr virus and human herpesvirus 8 .
  11. 11.  These viruses are neurotropic and establish latent infections in ganglionic neurons during primary infection, subsequently reactivating to cause recurrent disease or subclinical virus shedding, promoting spread to new hosts.  Associated diseases include peripheral neuropathies such as postherpetic neuralgia, Bell’s palsy, and potentially life-threatening encephalitis . HERPESVIRUSES
  12. 12.  Pathologically, HSV-1 results in a necrotizing infection involving the :  inferomedial aspect of the temporal lobes.  the inferior frontal cortex .  the cingulate cortex .  the subfrontal and insular regions.  Further progression of disease may result in petechial hemorrhages and eventual cavitation Herpes simplex virus 1 (HSV-1)
  13. 13.  CT is often normal, although non-specific hypoattenuating lesions in the temporal and/or frontal lobes with or without enhancement and superimposed hemorrhage may be demonstrated in severe illness .  MRI can be normal in up to 10% of patients.  The most characteristic pattern finding is unilateral high T2 signal involving the insula, medial temporal and inferior frontal lobes with or without involvement of the adjacent limbic structures.  Enhancement and hemorrhage become more prominent with disease progression Herpes simplex virus 1 (HSV-1)
  14. 14.  51-year-old diabetic woman with fever and confusion. (a) Unenhanced axial CT scan shows no significant changes in the left temporal lobe. (b) 2 days later unenhanced axial CT scan is still unremarkable. (c) 14 days later, unenhanced axial CT scan shows marked hypodensity in the left temporal lobe Herpes simplex virus 1 (HSV-1)
  15. 15.  Axial fluid attenuated inversion recovery image (A) demonstrates a region of increased signal intensity in the right temporal lobe . Herpes simplex virus 1 (HSV-1)
  16. 16. Herpes simplex virus 1 (HSV-1) Axial T1 Image demonstrate curvilinear regions of high T1 signal intensity within the right temporal lobe (arrow,), compatible with petechial hemorrhage in this patient with herpes encephalitis.
  17. 17. DWI demonstrates regions of patchy restricted diffusion and may be more sensitive than T2-weighted or FLAIR imaging in depicting regions of encephalitis Herpes simplex virus 1 (HSV-1)
  18. 18.  DWI classic herpes encephalites note abnormal hyperintense signal abnormallity in bilateal mesial temporal corex . Herpes simplex virus 1 (HSV-1)
  19. 19.  classic herpes encephalites note abnormal hyperintense signal abnormallity in bilateal mesial temporal corex & cingulate gyri on T2 & FLAIR images with reduced diffusivity. Herpes simplex virus 1 (HSV-1)
  20. 20.  T1 with contrast
  21. 21.  HSV-2 may result in severe neonatal encephalitis, with transmission most commonly occurring through an infected birth canal .  Pathologic examination demonstrates diffuse parenchymal and leptomeningeal inflammation which can progress to hemorrhage and necrosis.  MR demonstrating loss of gray–white differentiation and high T2 signal within the periventricular and subcortical white matter, with relative sparing of the central gray matter (basal ganglia, thalami) and posterior fossa. Herpes simplex virus 2 (HSV-2)
  22. 22.  With disease progression, decreased T2 signal intensity within the cortex may develop corresponding to the presence of focal hemorrhagic necrosis and parenchymal calcifications .  Severe cerebral sequelae such as cystic encephalomalacia or hydranencephaly may eventually be seen with more advanced disease Herpes simplex virus 2 (HSV-2)
  23. 23.  Cortical blurring and gyral/leptomeningeal enhancement in neonatal HSV-2 encephalitis in different patients.  A Axial T2-weighted image demonstrates reduced cortical gray white matter differentiation (arrowheads) in the right temporal lobe.  B Gyral/leptomeningeal contrast enhancement (arrows) in the right temporal region on the coronal image after gadolinium administration in the same patient .
  24. 24.  a Axial FLAIR image is normal in this 13-day old patient presenting with signs of sepsis and culture negative meningitis 2 days prior to this examination. No abnormality was seen on any of the conventional MR images . Herpes simplex virus 2 (HSV-2) Axial DW image demonstrates a focus of restricted diffusion (arrow) in the uncal region of the medial anterior left temporal lobe,
  25. 25.  Axial DW image demonstrates restricted diffusion in the left caudate nucleus head (arrowhead) and the right lentiform nucleus (arrow) in addition to the left occipitotemporoparietal and right parietal regions Herpes simplex virus 2 (HSV-2) Axial CT image of the same patient as in a obtained 3 years later demonstrates cystic encephalomalacia in the left occipito- temporo-parietal region (asterisk). There is also hypoattenuation in the left caudate nucleus head (arrowhead) and the right lentiform nucleus (arrow), indicative of old necrosis.
  26. 26.  Axial DW image in another patient demonstrates restricted diffusion in the pons (arrow) and deep cerebellar hemispheres (arrowheads). Herpes simplex virus 2 (HSV-2) End-stage neonatal HSV-2 encephalitis This axial noncontrast CT image demonstrates severe necrotic changes and encephalomalacia involving the frontal and parietal lobes bilaterally. The relative prominence of the basal ganglia (arrowheads) and thalami (arrows)
  27. 27.  Meningoencephalitis with MRI demonstrating diffuse, multifocal areas of high T2 signal intensity within the cerebral cortex.  Diffuse encephalitis results in non-specific regions of high T2 signal within the white matter.  VZV involvement of large vessels at the base of the brain may result in a variety of pathologic findings, ranging from necrotizing arteritis to remote vascular occlusion within the small blood vessels of the brain resembling atherosclerotic disease. Varizella-zoster virus (VZV)
  28. 28.  The spread of VZV from blood vessels to the ependymal cells lining the ventricles may result in ventriculitis, resulting in abnormal ependymal enhancement and high T2/FLAIR signal intensity.  spread of VZV to oligodendrocytes can result in a multifocal leukoencephalopathy which manifests as subcortical high T2 signal plaques which may demonstrate enhancement after gadolinium contrast administration Varizella-zoster virus (VZV)
  29. 29. Varicella-zoster virus encephalitis with multifocal vasculopathy. Axial fluid attenuated inversion recovery (FLAIR) (A) and T2-weighted image (B) demonstrate high FLAIR signal in the left caudate nucleus and in the posterior limb of the internal capsule as well as hyperintense T2 signal along the right paramedian frontal lobe. Magnetic resonane angiogram (C) demonstrates irregular narrowing in the left proximal middle cerebral and right anterior cerebral artery.
  30. 30.  Magnetic resonance image of a 6-month-old boy. (a, b) Axial T2 gradient echo sequence: blood in the ventricles and hydrocephaly. (c) Axial TI sequence after gadolinium infusion: no abnormal enhancement. (d) FLAIR sequence: no parenchymal abnormality.
  31. 31.  Magnetic resonance image of a 35-year-old man. (a-c) Cranial magnetic resonance image, FLAIR sequence showing punctiform hyperintensities subcortical (right frontal and left temporal) and in the pons. (d) Sagittal dorsal spinal cord, T2 sequence: hypersignal at the T7-T8 level.
  32. 32.  Magnetic resonance image of a 20-year-old man. Narrowing of the Ml segment of the middle cerebral artery.
  33. 33. Epstein-Barr virus (EBV)  EBV infection of the nervous system is uncommon but may result in meninigitis, encephalitis, myelitis, and/or cranial nerve palsies .  CT findings are often normal .  MRI may demonstrate non-specific high signal intensity within the cerbral cortex, at the gray–white junction, and/or within the deep nuclei (basal ganglia, thalamus) on T2-weighted images which may resolve on subsequent imaging.
  34. 34.  case reports of progression to hemorrhagic encephalitis have been published and should be a consideration with worsening neurologic deficits.  EBV infection has a high association with primary CNS lymphoma in the setting of acquired immune deficiency syndrome (AIDS) . Epstein-Barr virus (EBV)
  35. 35. Epstein–Barr virus. Axial T2-weighted image (A) imaging demonstrates abnormal increased signal in the right temporal lobe. Axial T2-weighted image (B) performed 3 days later demonstrates progression of abnormal signal in the right temporal lobe.
  36. 36.  Anon-contrast CT scan (C) performed the same day demonstrates partial hemorrhagic conversion of the lesion with adjacent swelling and right-to-left midline shift.
  37. 37.  Initial MR imaging of the patient. T1-weighted image does not reveal any abnormality (A). T2-weighted image depicts high signal intensity in the SCC (B). Turbo spin-echo FLAIR sequence shows additional high signals in both posterior hemispheres (C). All lesions had clearly elevated diffusion coefficients with high signal intensity on DWI (D), whereas ADC maps in the splenium were decreased (E). The T1-weighted image with gadolinium shows no contrast enhancement.
  38. 38.  Brain MRI scan findings in a 12-year-old boy with Epstein–Barr virus encephalitis. The scans were performed 1 day before the patient died. (A,B) These axial diffusion-weighted images show focal lesions of increased signal intensity— indicative of cytotoxic edema in the cerebellum, brainstem, basal ganglia and hippocampus—scattered throughout the subcortical white matter and cerebral cortex. Ventricles are not significantly narrowed. (C) Sagittal T1-weighted image that shows generalized cerebral edema with herniation of the brainstem and cerebellar tonsils into the foramen magnum.
  39. 39.  CMV infection of the nervous system is most often seen with immunocompromised patients .  CMV is the leading cause of congenital CNS infection, with an incidence of approximately 1–2% of live births.  The resultant imaging findings reflect the distribution of disease: meningitis, encephalitis, ventriculoencephalitis, myelitis, and retinitis .  CT imaging is less sensitive than MRI and may demonstrate non-specific cortical atrophy and/or decreased attenuation within the white matter .  With contrast-enhanced imaging, periventricular enhancment may be present, indicative of underlying ventriculoencephalitis . Cytomegalovirus (CMV)
  40. 40.  MRI demonstrates non-specific increased T2 and decreased T1 signal abnormalities in the white matter which may have a patchy or confluent distribution .  Nodular increased T2 signal abnormalities may also be noted within the brainstem, basal ganglia, cerebellum, and hippocampus, some of which may undergo hemorrhagic transformation.  Occasionally, CMV infection may present as a ring- enhancing cerebral mass with marked edema mimicking an intracranial neoplasm. Cytomegalovirus (CMV)
  41. 41.  CT imaging in infants with congenital CMV infection classically shows intracranial calcifications in a periventricular distribution, hydrocephalus, cortical atrophy, subdural hematomas, or effusion and non- specific white-matter hypodensities  CMV infection early in utero results in abnormal fetal brain development, migrational, cortical gyral abnormalities, delayed myelination, cerebellar hypoplasia and porencephalic cysts. Cytomegalovirus (CMV)
  42. 42. In uterocytomegalovirus (CMV) infection. Coronal true inversion recovery image demonstrates thickened and disordered cortex in the right frontal and temporal lobes (arrows) compatible with pachygyria in this infant within uteroCMV infection.
  43. 43. In utero cytomegalovirus (CMV) infection. Axial non-contrast computed tomography scan of the head demonstrates massive hydrocephalus as well as bilateral periventricu-lar calcifications in this infant with in utero CMV infection.
  44. 44. In uterocytomegalovirus (CMV) infection. Coronal T2-weighted image demonstrates thickened and disordered cortex in the right frontal and temporal lobes (arrows) compat-ible with pachygyria in this infant with in utero CMV infection.
  45. 45.  Axial (a) T1 and (b) T2 weighted MRI show mild ventricular dilatation and multiple tiny nodular T2 high-signal intensity lesions in basal ganglia and right frontal subcortical white matter without definite periventricular signal change. (c) Axial fluid attenuated inversion recovery image shows thin curvilinear high-signal intensities along the walls of both lateral ventricles and multifocal faint high-signal intensities at right frontal and basal ganglia regions. (d) Axial contrast enhanced T1 weighted image shows subtle subependymal enhancement (arrow). (e,f) Diffusion weighted image shows striking curvilinear high-signal intensities along the ventricular wall with a subtle low apparent diffusion coefficient value (arrow).
  46. 46.  Reactivation of latent HHV-6 infection in immunocompromised patients, may result in an encephalitis, leptomeningitis, or neuritis .  The most common findings include symmetric or asymmetric high T2 signal within the uncus, amgydala, and hippocampal body with extension to the rhinal cortex .  DWI may show the earliest signs of the underlying inflammatory changes with patchy regions of restricted diffusion in the involved neural tissue Herpes simplex virus 6 (HSV-6)
  47. 47. Herpes simplex virus 6 (HSV-6) Human herpesvirus-6 (HHV) infection. Axial fluid attenuated inversion recovery image of the brain demonstrates symmetric high signal abnormalitywithin the limbic system in this patient who developed HHV-6 infection after a bone mar- row transplant for treatment of lymphoma.
  48. 48. Flaviviruses
  49. 49.  Humans typically acquire infection through the bite of an infected mosquito or tick .  The major human pathogens among the Flavivirus genus are yellow fever virus, Dengue virus, Japanese encephalitis virus (JEV), St. Louis encephalitis virus (SLEV), tick-borne encephalitis virus (TBEV), and WNV  ( West Nile virus ). Flaviviruses
  50. 50.  JEV primarily affects developing neurons in thalamus, hippocampus, and midbrain, while anterior horn cells of the spinal cord and brainstem are the primary targets of TBEV.  The disease spectrum of JEV ranges from non-specific febrile illness to aseptic meningitis, meningoencephalitis, flaccid paralysis, and encephalitis .  Parkinsonian movement disorder and seizures have also been reported. Clinical syndromes associated with WNV include meningitis, encephalitis, and acute flaccid paralysis Flaviviruses
  51. 51. St. Louis encephalitis (SLE)  SLE is transmitted through a mosquito-borne virus and has resulted in several epidemics in the eastern and central United States .  perivascular inflammatory changes with neuronal degeneration and microglial proliferation, most prominent within the substantia nigra , pons ,insular cortex and thalami
  52. 52.  St. Louis encephalitis. Axial T2-weighted images demonstrate symmetric increased signal intensity involving the insular cortex and thalami as well as the substantia nigra, midbrain, and pons St. Louis encephalitis (SLE)
  53. 53. West Nile encephalitis  West Nile encephalitis is an emerging infection with a rapid increase in incidence and geographic range.  Transmission is most often through a mosquito- infected vector, although transmission through breastfeeding, transplacental has been reported .  Imaging findings in cases of West Nile encephalitis are non-specific, with a case series reporting increased T2 signal abnormality most often within the mesial temporal lobe and midbrain .  Meningeal, cerebellar, cortical, and white-matter imaging abnormalities are less commonly found .
  54. 54.  West Nile encephalitis. Axial fluid attenuated inversion recovery images (A, B) demonstrate increased signal in the thalami and corpus striatum. Increased signal intensity is also noted in the medial temporal lobes and cerebellum (curved arrow,B). Axial T1 postcontrast image (C) demonstrates enhancement in the thalami. West Nile encephalitis
  55. 55. Japanese encephalitis  Japanese encephalitis (JE) is the most frequent global cause of mosquito-borne encephalitis and is associated with significant morbidity and mortality.  Pathology studies have demonstrated diffuse inflammatory changes involving the basal ganglia, thalamus, cerebral cortex, brainstem, and cerebellum.  The most consistent finding on MRI is bilateral increased T2 signal abnormality in the thalami with or without hemorrhage.
  56. 56. Japanese encephalitis Japanese encephalitis. Axial fluid attenuated inversion recovery images in two different patients with Japanese encephalitis demonstrate bilateral symmetric increased signal intensity (A) and asymmetric right thalamus signal abnormality B) respectively.
  57. 57. Bunyaviridae
  58. 58.  Between the period of October 2003 and April 2005 an epidemic of RVF encephalitis appeared in the region of Khafer Al-Sheikh Governorate.  Humans can get RVF as a result of bits from mosquitoes and possibly other blood sucking insects that serve as vectors. Humans can also get the disease if they are exposed to either the blood or other body fluids of infected animals.
  59. 59.  MRI of the brain demonstrated the following: patchy areas of edema targeting the cortical and subcortical deep white matter and diffusely involving both cerebral hemispheres. These were evident in the temporal, frontal, perisylvian and occipitoparietal regions. Patchy involvement of the mesencephalon, basal ganglia and posterior nuclei of both thalami .  the affected tissues are emitting subtle decrease in signal intensity on T1-Weighted images and bright signal intensity on T2-weighted and FLAIR pulse sequences  . No associated enhancement or leptomeningeal reaction.
  60. 60.  C.T brain scan demonstrate gray matter affection with diffuse white matter affection & mainly in the region of basal ganglia
  61. 61.  MRI of the brain T2 weighted images demonstrate evidence of gray matter affection with diffuse white matter edema
  62. 62. Arenaviruses
  63. 63. Arenaviruses  Lymphocytic choriomeningitis virus can cause aseptic meningitis (rarely fatal), hydrocephalus, and more severe CNS disease.  Transmission to human via contact with rodents .  Encephalitis develops in 5–34% of patients.
  64. 64. lymphocytic choriomeningitis virus (LCMV)  prenatal disease may result in devastating neuroteratogenic effects.  the most common abnormalities included microcephaly and periventricular calcification. Other additional abnormalities included prominent gyral malformation, ventriculomegaly, hydrocephalus, porencephalic and periventricular cysts, encephalomalacia, and isolated cerebellar hypoplasia
  65. 65.  2 children with congenital LCMV infection (B, C). (B) The most common abnormalities in congenital LCMV infection include periventricular calcifications (arrows) and ventriculo-megaly (V), often due either to noncommunicating hydrocephalus or to cerebral atrophy. (C) Some patients with congenital LCMV infection have regions of encephalomalacia (*), reflecting focal tissue destruction. In addition to massive encephalomalacia, this patient has periventricular calcifications (arrow). LCMV, lymphocytic choriomeningitis virus.
  66. 66.  (B) In congenital LCMV infection, the virus can impair cerebellar growth and lead to cerebellar hypoplasia (arrow).
  67. 67. Retroviruses
  68. 68. Retroviruses  The major human retroviruses include human T lymphotropic viruses 1 and 2 and HIV-1 and -2.  Both HTLV-1 and HTLV-2 have been associated with HTLV-associated myelopathy/ tropical spastic paraparesis, a chronic progressive demyelinating disease that affects the spinal cord and white matter of the CNS.
  69. 69. Retroviruses  HIV-associated neurologic disorders include neurocognitive disorders and peripheral neuropathies as well as vacuolar myelopathy  Other primary neurologic syndromes associated with HIV include aseptic meningitis, multiple sclerosis-like disorders, ischemic and hemorrhagic strokes, primary HIV-induced headache and psychiatric disorders.
  70. 70.  Early changes of HIV encephalitis manifest as multifocal subcentimeter white-matter lesions appearing bright on T2-weighted images. These are generally symmetric and spare the subcortical U- fibers.  The chronic stage of HIV infection manifests as progressive white-matter signal abnormality in conjunction with brain atrophy.  With progression of disease, however, these become confluent and may extend to involve the basal ganglia, cortex, cerebellum, brainstem, and spinal cord Human immunodeficiency virus
  71. 71.  Another chronic feature of HIV infection is progressive cerebral atrophy, which is most prominent centrally, resulting in ex vacuo ventricular dilatation out of proportion to sulcal prominence. Human immunodeficiency virus
  72. 72. Polyomaviruses
  73. 73.  The first human members of family Polyomaviridae, JC virus (JCV) and BK virus (BKV) (both of genus Orthopolyomavirus).  Reactivation of latent JCV in immune-compromised individuals may cause PML. Polyomaviruses
  74. 74. Progressive multifocal leukoencephalopathy  PML is most commonly seen in the setting of underlying HIV-1 infection, it may also be seen in the context of hematologic malignancies and treatment with immunosuppressive medications.  Lesions appear hyperintense on T2-weighted images and hypointense on T1-weighted images.  Lesions are most commonly found in the subcortical and periventricular white matter of the frontal and parieto-occipital lobes; they are also seen in the white matter of the cerebellar peduncles or hemispheres, and in the brainstem
  75. 75.  Early on, the lesions may be small but then progress to form larger areas of involvement, often with a scalloped border.  The lesions are classically bilateral, asymmetric, multifocal, and lacking in mass effect. Only 9% of cases demonstrate enhancement, which is typically faint and peripheral .  Spinal cord involvement is rare. Progressive multifocal leukoencephalopathy
  76. 76.  This is an MRI of the brain of a PML survivor (PML-S). On the left is a fluid attenuated inverse recovery (FLAIR) image, which shows a large hyperintense lesion in the left cerebral hemisphere, sparing the cortex. On the right is the corresponding T1 with gadolinium (contrast) image, which shows no enhancement within the hypointense PML lesion.
  77. 77.  This is an MRI of the brain of a PML- survivor. On the left, FLAIR image shows a large hyperintense lesion in the white matter of the left hemisphere. There is also a shift of the midline (arrow) and disappearance of the sulci (arrowheads), signifying mass effect, as seen in excessive inflammation. On the right is the corresponding T1+Gad image; the arrows show enhancement within the PML lesion. Progressive multifocal leukoencephalopathy
  78. 78. Paramyxoviruses
  79. 79. Paramyxoviruses  Measles virus infections can lead to three neurologic diseases.  Acute disseminated encephalomyelitis that occurs about a week after the rash phase .  inclusion body encephalitis in immune-suppressed individuals .  subacute sclerosing panencephalitis .  Aseptic meningitis is the most common neurologic manifestation of mumps virus infection.
  80. 80. Subacute sclerosing panencephalitis (SSPE)  SSPE is a chronic and progressive encephalitis caused by a persistent infection of the brain by measles virus.  Early changes include bilateral, multifocal, asymmetric T2 hyperintense lesions of the periventricular and subcortical white matter .  There is a predilection for involvement of the parietal and occipital lobes .  With time, these lesions may become larger, more numerous, and more confluent, and appear more symmetric. Late changes of SSPE include abnormal signal in the basal ganglia (typically the putamen),
  81. 81. subacute sclerosing panencephalitis (SSPE). Axial T2-weighted image demonstrates symmetric regions of increased signal intensity in the subcortical white matter, predominantly in the posterior cerebrum. Serology titers and electroencephalogram findings were compatible with SSPE.
  82. 82. Rhabdoviruses
  83. 83. Rhabdoviruses  Rabies virus transmitted through skin by animal bites the virus is transmitted directly to peripheral neurons and then to the brain, or neuronal transmission occurs after amplification in skeletal muscles.  Disseminated infection, including transmission from the brain to salivary glands, occurs late in disease.
  84. 84. Rabies encephalitis  MR features of rabies encephalitis describe ill- defined mild areas of T2 hyperintensity in the brainstem, hippocampi, hypothalami, deep and subcortical white matter, and deep and cortical gray matter .
  85. 85. Picornaviruses
  86. 86.  that include viruses of humans are Enterovirus, Hepatovirus, and Parechovirus. The human enteroviruses include poliovirus types 1–3, coxsackieviruses, echoviruses, and rhinoviruses.  Neurologic diseases include the flaccid paralysis of polio, aseptic meningitis, and encephalitis Picornaviruses
  87. 87. Enteroviral encephalitis  EV71 characteristic MR findings are hyperintensity in the posterior portions of the medulla and pons,  Severe cases demonstrated involvement of the ventral horns of the spinal cord, basal ganglia, and thalami.  The MR finding most characteristic of poliomyelitis is hyperintensity involving the region of the anterior horn cells on T2-weighted images .
  88. 88. Enteroviral encephalitis. Axial T2-weighted image demonstrates symmetric regions of increased signal intensity involving the posterior pons
  89. 89. Orthomyxoviruse s
  90. 90. Orthomyxoviruses  Influenza viruses A, B, and C are well known as the causes of influenza.  Neurologic manifestations of influenza virus include Reye’s syndrome, febrile seizures, encephalitis, myelitis, and acute necrotizing encephalopathy (ANE).  ANE is characterized by bilaterally symmetric necrotic brain lesions in the thalami, cerebral white matter, brainstem, and cerebellum .
  91. 91.  Influenza A. Axial fluid attenuated inversion recovery (A)andT1postcontrastimage(B) demonstrate bilateral asymmetric non-enhancing regions of high signal intensity involving the thalami. A peripheralrim of restricted diffusion is demonstrated on the diffusion-weighted images (arrow,C). The imaging findings are consistent with acute necrotizing encephalopathy in this patient with serologic titers positive for underlying influenza A infection. Influenza

×