Acute Disseminated Encephalomyelitis (ADEM)
Acute disseminated encephalomyelitis (ADEM) Is an immune-mediated demyelinating disease of CNS involving white matter in the brain and spinal cord. Grey matter (basal ganglia, thalamus, and even cortical grey matter) may be involved.
- Acute disseminated encephalomyelitis (ADEM)
- Is an immune-mediated demyelinating disease of CNS
- Involves white matter in the brain and spinal cord.
- Grey matter (basal ganglia, thalamus, and even cortical grey matter) may be involved.
- ADEM is a rare illness
- Estimated 1 in 125,000-250,000 individuals affected each year.
- It mostly occurs in children (majority <10 yr, remainder 10-20yr)
- More commonly in males than in females (male to female ratio 1.3:1)
- More common in winter and spring
- Post-infection (67%)
- Genetic susceptibility (rarely)
Table 1: Etiological factors of ADEM
Japanese B encephalitis
- Molecular mimicry
- T cell-mediated inflammation
Antibodies formed against myelin basic protein (MBP), myelin-associated oligodendrocyte basic protein (MOBP), oligodendrocyte specific protein (OSP), myelin oligodendrocyte glycoprotein (MOG), myelin-associated glycoprotein (MAG), and proteolipid protein (PLP).
- Priming and activation
- Recruitment and effector phase and resulting into
- Infiltration of lymphocytes and macrophages in the small blood vessels of both white and grey matter
- Endothelial swelling
- Vessel wall invasion by inflammatory cells
- Perivascular edema
- As the lesions become older, at a late stage of disease foci of fibrillary fibrosis can also be seen in adjacent brain tissue.
The characteristic feature of ADEM develops rapidly.
- Acute cognitive dysfunction
- Behavioral changes
- Other neurologic abnormalities:
- Optic neuritis
- Urinary retention
- Elevated intracranial pressure
- Extrapyramidal signs
According to the International Pediatric Multiple Sclerosis Study Group (IPMSSG), 4 diagnostic criteria are required to make a diagnosis of ADEM in children.
- Multifocal, clinical CNS event with a presumed inflammatory demyelinating cause
- Encephalopathy that cannot be explained by fever, systemic illness, or post-ictal fever
- No new clinical and MRI findings 3 months or more after the onset
- Brain MRI is abnormal with changes consistent with demyelination during the acute, 3-month phase.
- Monophasic ADEM
- single episode with no further demyelinating events more than 3 months after onset.
- Multiphasic ADEM
- Two episodes separated by at least 3 months in time. More than two episodes suggest an alternate disease process.
- Any episode of ADEM plus one or more episodes of optic neuritis.
- Acute hemorrhagic encephalomyelitis (AHEM)
- Fulminant presentation associated with multifocal hemorrhages and necrosis.
- Aseptic meningitis
- Bell's palsy
- Brain metastasis
- Cardioembolic stroke
- Cauda equina and conus medullaris syndrome
- Cavernous sinus syndromes
- Central nervous system complications in HIV
- Cerebral venous thrombosis
- Churg-Strauss disease
It is important to diagnose a patient with either condition accurately because the approach to the treatment of the two conditions differs significantly. (Figure 1 & 2)
Differentiating Features of ADEM and Multiple Sclerosis
Infection or vaccination
No recognizable infection or vaccination
Meningism, stupor, focal signs
Non progressive, monophasic
Relapsing and remitting, progressive
Diffuse, bilateral symmetrical lesions
Periventricular black holes
Recovery is rapid and often complete
Recovery is variable
Figure 1: (Left) ADEM, showing bilateral enhancing lesions of variable size throughout both cerebral hemispheres in the deep white matter, juxta-cortical regions, and left thalamus. (Right) MS, showing periventricular hyper intensities typical of multiple sclerosis plaques.
- Leucocytosis, predominately lymphocytosis
- Raised platelets
- Raised CRP and ESR
- Culture of throat, nasopharynx, stool, and CSF
- Serology testing for a variety of agents such as influenza, EBV, herpes, and mycoplasma, etc.
- Raise RBC and WBC
- Increase protein concentration
- Increase myelin basic protein
- Rarely elevated IgG index
- Oligoclonal bands in up to 29 % of cases
- ADEM lesion characteristics
- It may be symmetric or asymmetric
- Poorly marginated
- The periventricular area is spared (which is involved commonly in MS)
- Located in deep and subcortical and central white matter, cortical gray-white matter junction, and deep gray matter of the basal ganglia, thalami, cerebellum, brainstem.
- Best modality used in the diagnosis of ADEM and is best defined in T2, FLAIR &
- T2-weighted images
- Fluid-attenuated inversion recovery (FLAIR) sequences
- Proton density, or echo-planar trace diffusion techniques
- most often unremarkable
- In later stages, ADEM may appear as focal or multifocal regions of white matter damage.
- Disturbed sleep pattern
- Focal or generalized slowing of electrical activity, typical of encephalopathy
- Seizure activity may also be noted
- Antibiotic or Acyclovir until an infectious agent is ruled out
- High dose IV methylprednisolone 30 mg/kg/day up to a maximum dose of 1000 mg per day for 3-5 days
- Oral treatment at dose of 1-2 mg/kg/day is continued and gradually tapered over a period of 4-6 weeks to reduce risk of relapse
- 1gm/kg/day IV for 2-5 days
- Recommended for <1 year age
- No response to steroids in 48-72 hours
- Induction Dose up to 2 g/kg in 2 to 5 divided doses.
- Follow‐up Dose -1 g/kg followed by a second dose (if required) after 4 to 6 weeks for extended monophasic ADEM
- Recurrent cases
- Induction Dose up to 2 g/kg in 2–5 divided doses
- Maintenance Dose ‐ 1 g/kg, 4–6 weekly
- Acute hemorrhagic leucoencephalitis, AHLE
- Recommended for patient not responding to both steroid and IVIG
- Surgical intervention is indicated in cases of elevated intracranial pressure and hemorrhagic brain purpura as a result of AHLE by
- Lumboperitoneal shunt
- Bilateral optic nerve decompression
- Decompression of the intracranial fossae by unroofing of the cranium
- <5 years age show excellent recovery
- Early rehabilitation program is required in case of cognitive impairment, epilepsy, visual and motor deficits (weakness, spasticity, ataxia), and impairment in speech
- Children with ADEM show a slow and complete recovery in four to six weeks
- Adults with ADEM have increased rates of hospitalization, intensive care unit admission, and mortality compared to pediatric patients
- 60 % do not show any neurologic deficits.
- Neurologic deficits present in the form of transverse myelitis, behavioral problems, and cognitive impairment mostly in <5 years old.
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