Acute Disseminated Encephalomyelitis

  • Etiology:
    — Immune mediated leukoencephalopathy and demyelination involving brain which may involve cord
    — Inflammatory disorder which predominantly affects white matter of brain and spinal cord
    — Inflammatory process surrounding veins and venules of central nervous system
    — May follow viral infection or vaccination or certain drugs as antibodies to viral particles may cross react with myelin proteins leading to demyelination
  • Imaging MRI of Brain Lesions:
    — Multiple usually large white matter lesions with asymmetric distribution
    — Predilection for occipital and parietal regions of cerebral hemispheres
    — Lesions often spill into adjacent cortex
    — Basal ganglia and thalamic involvement in 25%
    — Most lesions do not enhance
    — Lesions regress over weeks to 18 months
    — DWI in active lesions shows diffusion restriction
    — Spinal involvement very common (unlike multiple sclerosis)
  • Imaging MRI of Spinal Cord Lesions:
    — Peripheral-posterolateral location in cord
    — Less than 2 vertebral body segments in length (short segment)
    — Less than 1/2 cross sectional area of cord
    — Enhancement related to activity
  • DDX: Transverse myelitis
    — Central location in cord
    — Greater than 2 vertebral body segments in length (long segment)
    — Greater than 1/2 cross sectional area of cord
    — Enhancement absent or patchy
    — No restricted diffusion
    — Smooth cord enlargement
  • Complications:
  • Treatment:
  • Clinical:
    — Seen post-viral infection (measles or influenza) or post-vaccination (10%)
    — Transient
    — Monophasic
    — Responds to steroids
    — Associated with Ebstein Barr virus and cytomegalovirus and mycoplasma pneumonia

Multiple sclerosis

  • Demyelinating disorder, 5% of cases begin in childhood
  • Dysregulated immune system leading to CNS injury
  • Dissemination in space – MRI with greater than 1 hyperintense T2WI lesion characteristic of multiple sclerosis in at least two multiple sclerosis typical regions of CNS – periventricular, cortical or juxtacortical, infratentorial, spinal cord
  • Dissemination in time – MRI with new lesions on followup exam
  • Periventricular lesions in 86% children with multiple sclerosis, multiple calloseptal or periventricular T2 hyperintensities that are perpendicular to lateral ventricles (Dawson fingers)
  • Juxtacortical lesions – Lesions abutting the cortex
  • Infratentorial lesions – Posterior fossa lesions 25% more frequent in children
  • Brainstem lesions in 61%
  • Tumefactive lesion rare in children, greater than 2 centimeters in size, usually single, have mass effect and edema, commonly supratentorial, shows similar MRI features and evolution to standard lesions
  • Contrast enhanced lesions – More inflammatory than adult-onset multiple sclerosis, up to 70% have enhancing lesions on baseline MRI, punctate or nodular or linear or incomplete ring, with or without leptomeningeal enhancement on delayed FLAIR images as marker for cortical demyelination
  • Black holes – Non-enhancing T1-hypointense lesions indicate chronicity and are result of severe demyelination or axonal loss, presence of greater than than or equal to 1 black hole at baseline is single strongest predictor of multiple sclerosis
  • Spinal cord – Variable frequency, may be clinically silent, short focal increased T2 lesions that are less than 2 vertebral body segments in length and less than half the cross sectional area of cord and are commonly in lateral and posterior columns
  • Optic neuritis – Typically unilateral, short segment involvement, less contrast enhancement, with or without restricted diffusion

Multiple Sclerosis

  • Sharply demarcated lesions in periventricular, juxtacortical, infratentorial and spinal cord
  • Corpus callosum – Calloso-septal interface
  • Dawson’s fingers – Periventricular distribution along Virchow-Robin spaces perpendicular to lateral ventricles in oval configuration
  • Dissemination in space – Here and there – more than one place in CNS – juxtacortical, periventricular, infratentorial, spinal cord
  • Dissemination in time – New and old – damage occurred more than once – lesions with and without enhancement, lesions with and without DWI, new lesions at followup MRI

Myelin oligodendrocyte glycoprotein antibody associated disease (MOGAD)

  • Inflammatory disorder of CNS characterized by immune mediated demyelination
  • Characteristic features – Optic neuritis, acute disseminated encephalomyelitis, transverse myelitis
  • Younger children – Acute disseminated encephalomyelitis more common, older children – optic neuritis or transverse myelitis more common
  • MOGAD diagnostic criteria – Anti-MOG antibodies plus optic neuritis, transverse myelitis, acute disseminated encephalomyelitis, cerebral syndrome or encephalitis, brainstem syndrome, seizures
    — Optic neuritis – Most common manifestation, bilateral in 84%, long segment involvement with anterior greater than posterior segments, enhancement of perioptic nerve sheath and surrounding orbital fat in 50-80%, responds well to steroids
    — Spine – Common in up to 33%, mild symptoms despite extensive cord lesions, typically long segment of greater than 3 vertebral body segments, increased T2 of gray matter (H-sign), common involvement of conus medullaris
    — Brain – Ill-defined lesions of white matter and gray matter, deep gray matter common, lesions may converge into leukodystrophy-like pattern, enhancement less defined compared with multiple sclerosis, 1/3 lesions are infratentorial often in brainstem, cerebellar peduncle type, can show substantial resolution in followup
    — Brain – Cerebral cortical encephalitis, FLAMES – FLAIR hyperintense lesions in anti-MOG-associated encephalitis with seizures
    — Majority are unilateral and accompanied by cortical swelling and leptomeningeal enhancement

Neuromyelitis Optica Spectrum Disorders (NMOSD) aka Devic disease

  • Recurrent episodes of optic neuritis and transverse myelitis
  • Inflammatory disorder of CNS due to severe immune-mediated demyelination and axonal damage that primarily targets optic nerves and spinal cord
  • Once thought to be a variant of multiple sclerosis, now considered a distinct entity
  • Diagnostic criteria – Anti-aquaporin-4 antibodies plus optic neuritis, transverse myelitis, area postrema syndrome, acute brainstem syndrome, narcolepsy or diencephalic syndrome, cerebral syndrome
    — Optic neuritis – In 75% of children, often bilateral, long segment involvement, can involve chiasm and extend into optic tracts
    — Spine – 1/3 initial presentation, transverse myelitis with patchy enhancement with central gray matter predominance and greater than 1/2 cross section
    — Brain – Diencephalic structures – hypothalamus, thalami, cloud like pattern of enhancement
    — Area postrema syndrome – On medial posterior surface of the medulla oblongata

Demyelination with encephalopathy – Think acute disseminated encephalomyelitis or MOGAD
Demyelination without encephalopathy – Think multiple sclerosis or NMO

Radiology Cases of Acute Disseminated Encephalomyelitis

MRI of acute disseminated encephalomyelitis / ADEM
Axial FLAIR MRI of the brain (upper and lower left) show multiple high signal intensity lesions primarily in the white matter as well as in the medulla that enhance on T1 MRI with contrast (upper right). Sagittal T2 MRI without contrast of the cervical spine (below right) shows high signal intensity expansile lesions in the spinal cord from C2 to C7 as well as from T2 to T3.
MRI of acute disseminated encephalomyelitis
Axial FLAIR MRI without contrast of the brain show multiple lesions in the centrum semiovale, periventricular white matter, splenium of the corpus callosum and white matter of the parietal and occipital lobes. There was no mass effect and no diffusion restriction associated with the lesions. No contrast was given as the patient was pregnant.