Autoimmune Encephalitides
Dr.Roopchand.P.SSenior Resident AcademicDepartment of Neurology
Introduction.
• Autoimmune Encephalitis resulting from an attack of the brain by the body's immune system– Acute Disseminated Encephalitis (ADEM)– Hashimoto's Encephalitis– Rasmussen's Encephalitis– NMDA-Receptor Antibody Encephalitis– Limbic Encephalitis
ADEM
• occurs in association with an immunization or vaccination (postvaccination encephalomyelitis) or systemic viral infection (parainfectious encephalomyelitis).
• perivascular inflammation, edema, and demyelination within the CNS in characteristic.
• Postvaccination Acute Disseminated Encephalomyelitis.– subject of medicolegal controversy.
• Measles-Induced Acute Disseminated Encephalomyelitis.– complicate 1 in 400 to 1 in 1000 cases of measles
infection.• Idiopathic Acute Disseminated
Encephalomyelitis– in the setting of nonspecific viral illness.
• bilateral ON• loss of consciousness,• Meningismus• loss of deep tendon reflexes and retained
abdominal reflexes in the presence of Babinski sign
• central body temperature over 100°F• severe shooting limb pains.
• development of a focal or multifocal neurological disorder following exposure to virus or receipt of vaccine.
• peak dysfunction within several days.• Recovery can begin within days• Complete resolution day to months.• Measles virus–associated ADEM may carry a
worse prognosis.
Investigations
• MRI: multifocal CNS lesions.– majority of the T2 lesions enhance, suggesting
they were of recent onset.– after several weeks, lesions show at least partial
resolution.• CSF:– Normal pressure, cells <100/mm3, moderate
increase in protein.– OCB not usually seen.
• The current favored therapy for ADEM is high-dose corticosteroids.
• Acute Hemorrhagic Leukoencephalitis.• Isolated ON• Cerebellitis• ATM.• c/c recurrent.
Hashimoto encephalopathy
• acute to subacute• evidence of cognitive impairment• variable psychiatric symptoms, alteration in
consciousness, hallucinations• Involuntary movements, seizures, myoclonus,
opsoclonus, chorea, ataxia, stroke like episodes, and myelopathy.
• Adolescent females are mostly affected.
• Diagnosis:– Clinical triad of neuropsychiatric symptoms,
detection of antimicrosomal or antithyroglobulin antibodies, and exclusion of other causes.
– antithyroid– peroxidase, antithyroglobulin, – lesser extent thyroid-stimulating hormone
receptor–blocking antibodies.– α-enolase
• autoimmune cerebral vasculitis perhaps related to immune complex deposition.
• CSF show moderately elevated protein, may be positive for anti thyroid Ab, OCB seen
• EEG: slowing, triphasic waves, epileptiform discharges.
• MRI usually normal, occasionally non-specific sub cortical white matter T2 signal changes.
• Thyroid status may be normal.• Treatment: short course high dose steroids
(55% full recovery)• Recurrence – continued steroids, IVIG, other
immunomodulatory drugs.
Rasmussen's encephalitis
• chronic focal encephalitis (CFE)• rare inflammatory neurological disease• frequent and severe seizures, loss of motor
skills and speech, hemiparesis encephalitis and dementia.
• Usually <15 yrs• Affects one cerebral hemisphere.
• auto-antibodies against the glutamate receptor GluR3.
• T lymphocyte mediated destruction of neurons.
• C/F:– mostly affects children(avg 6yrs)– prodromal stage ,Acute stage and residual stage.
• Diagnosis is usually clinical.• EEG shows slowing in affected hemisphere.• MRI : gradual shrinkage of the affected
hemisphere with signs of inflammation or scarring.
• Treatment:– Control of seizures– Steroids, IVIG– Severe cases Hemispherectomy.
Anti-NMDA receptor encephalitis:
• acute form of encephalitis.• Potentially Lethal.• caused by autoimmune reaction against NR1- and
NR2-subunits of the glutamate NMDA receptor.• Associated with ovarian teratomas.• Previously thought entirely as a paraneoplastic
manifestation.• psychiatric symptoms or memory problems,
seizures, unresponsiveness , dyskinesias, autonomic instability, hypoventilation.
• MC in young women and children.• Treatment with Steroids, IVIG.– PLEX– Cyclophosphamide and /or rituximab.
Limbic and Brainstem Encephalitis:
• Limbic encephalitis: Confusion,depression, agitation, anxiety, memory deficits, dementia, and partial complex seizures.
• Brainstem encephalitis: oscillopsia, diplopia, dysarthria, dysphagia, gaze abnormalities, and subacute hearing loss.
• Symptoms can overlap.
• MRI:– unilateral or bilateral mesial temporal lobe
abnormalities on T2-weighted and FLAIR images’– The temporal-limbic regions may be hypointense on
T1-weighted sequences and may enhance with contrast.
• Associated with testicular germ cell tumors, Hodgkin lymphoma, thymoma.
• Antigens:– Intra cellular: Hu, Ma2, CV2/CRMP5– Cell surface antigens: AMPA receptors, leucine-rich
glioma inactivated 1 (LGI1) and γ-aminobutyric acid type B [GABA-B] receptors.
Graus and Saiz criteria(2005)
All four of• Subacute onset (<12 weeks) of seizures, short-term
memory loss, confusion, and psychiatric symptoms• Neuropathologic or radiologic evidence (MRI, SPECT, PET)
of involvement of the limbic system• Exclusion of other possible aetiologies of limbic dysfunction• Demonstration of a cancer within 5 years of the diagnosis
of neurologic symptoms, or the development of classic symptoms of limbic dysfunction in association with a well-characterized paraneoplastic antibody (Hu, Ma2, CV2, amphiphysin, Ri)
Treatment:
• immunomodulation with steroids and IVIg.– The likelihood of improvement is higher if the
disorder is associated with antibodies to cell-surface receptors or ion channels.
• removal of the antigenic source (tumor) and antibodies with antibody depleting treatments are often successful.
• Treatment is disappointing when antigens are intracellular.
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