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Mar 1st - 15th 2001 Acute Disseminated Encephalomyelitis

(ADEM) (Please wait for the content to download)

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       A two-year old male child presented with high-grade fever, continuous with cough from last two days. There is history of sudden inability to move left side of body from last one day. There is no history of seizure/altered sensorium/speech disturbance. No History of vomiting, loose motions.
       On examination child is conscious, irritable, and slightly pale, without cyanosis, icterus, clubbing or lymphadenopathy. Heart rate of child is 90/min, BP - 90/68 mm Hg. All peripheral pulses are well palpable. Child is recognising parents, speech normal for age, no cranial nerve involvement. Tone, bulk, power, DTR and planter of right side are normal. Left side tone is decreased, bulk normal, power 3/5 both limbs, DTR positive. Abdominal, cremastric reflexes are absent and planter upgoing.
Contributed by Dr Sonia Makhija, New Delhi
Updates (Based on Responses)
Weight of the child is 10.4 kg. No respirtory distress. S₁, S₂ are normal. Per abdo is soft with no organomegaly. ENT examination rule out otitis media. There is no history of cyanosis in the past. There is no joint swelling. Mantoux done is negative. CSF examination cytology clear no cells, protein 34, sugar 22, chloride 134, sterile. Haemogram shows Hb 9.9 g%, TLC 15480, N₄₈L₄₄E₇M₁, platelet count 495000, microcytic hypochromic with anisocytosis platelets are adequate. C T scan shown below show hypodense lesion in right thalamus and right sub cortical region. The sickling test is negative. Chest radiograph of the child is normal.

Lesion on CT (I) are present in right thalamus and right sub cortical region which is not correlating with the dense hemiplegia and if we consider vascular cause for these lesions they do not fit into a vascular territory and hypo density is seen only in sub cortical white matter and not grey matter. So probably we are missing some lesions that are not visible on CT. In view of this MRI scan with angio was done. MRI (II & III) shows - Multiple symmetric bilateral lesions involving subcortical white matter bilaterally right sided basal ganglia which are hypo to isodense on T1 weighted and hyperdense on T2 weighted and flair pulse sequuense. Also involvment of posterior limb of internal capsule on the left and external capsule on right, suggestive of Acute disseminated encephalomyelitis syndrome. MRI Angio (IV) is normal. Follow up MRI (V) after five and half months show normal scan.
Pediaindia would like to acknowledge kind cooperation of Prof (Dr) S Aneja, Incharge, Division of Pediatric Neurology, Kalawati Saran Children's hospital, LHMC, New Delhi, who in spite of her busy schedule spared her valuable time and offered constructive suggestions.

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Introduction
Acute Disseminated encephalomyelitis (ADEM) is the inflammatory demyelinating, immune mediated, monophasic, and polysymptomatic disorder of the central nervous system white matter. It is usually followed by vaccination or viral infection. Multifocal symptoms involving various combinations of sensory, motor, gait, visual and memory disturbance or even as a psychiatric illness are seen. Most common age group affected is 1year to 20 years.
Etiology
A. Post infectious encephalomyelitis: Usually associated with viral exanthems - measles, varicella, vaccinia, rubella, mumps, herpes, and in some cases bacteria like mycoplasma pneumoniae and legionella. B. Post immunization encephalomyelitis: commonly seen with measles, mumps, rubella vaccination, also with semple antirabies and Japanese encephalitis. C. Post organ transplantation encephalomyelitis: Long term immunosuppression leads to increased risk of acute infection, thus leading to ADEMS. Immunosuppressive agents such as methotrexate, cyclosporine, cyclophosphamide have been implicated in white matter disease that resembles ADEMS.
Pathophysiology
It is predominantly a white matter disease with periventricular inflammation and demyelination. It is an auto immune response to central nervous system myelin.
Clinical features
Abrupt onset of multifocal neurological disorder accompanied by generalized complaints of headache, fever, vomiting and mental state changes. Maximal deficit is usually reached within several days. The usual focal and multifocal signs reflect cerebral (hemiparesis, aphasia), brain stem (cranial nerve involvement) and spinal cord (paraparesis) involvement. Peripheral nervous system involvement is seen in a few cases, especially in cases occurring after rabies vaccine. Recovery usually begins within few days with 50% cases having complete recovery. Mortality is around 30% in few studies. Features suggesting poor prognosis are hyperacute onset, coma and complicating seizures. Relapse is uncommon in cases with complete recovery. Some cases (~15%) also have monosymptomatic forms of postinfectious demyelinating disease like transverse myelitis, optic neuritis, cerebellar ataxia and acute hemiparesis. Atypical presentations like acute psychosis, hyperactivity, aggressiveness and evidence of PNS involvement are also known.
Diagnosis
EEG - moderately to severe diffuse high voltage theta delta activity. CSF - mild mononuclear pleocytosis, raised proteins, MBP content increased in 60%. Increased IgG index in < 10%. CT Scan: May be normal or may reveal areas of patchy low attenuation in the white matter with focal or diffuse cortical enhancement. CT scan lesions do not correspond to the extent or pattern of clinical disease. MRI Much more sensitive than CT Scan. Early MRI facilitates diagnosis and can lead to early treatment with possible favorable outcome. T2 weighted MR images reveal multiple areas of increased signal intensity throughout the central nervous system that often correspond to the patient's clinical deficit. T2 weighted images are more sensitive than T1 weighted in detecting abnormalities. Contrast enhancement is usually seen. The lesions are usually symmetrical and involve subcortical white matter and deep seated grey matter including basal ganglia, thalamus and cerebellum. Rarely MRI appearance is that of ring enhancing lesion.
Prognosis
Self remission in approx 30% cases, complete recovery in 50% cases, rarely relapsing disease, mortality in 30% cases.
Treatment
A. Steroids Glucocorticoids and ACTH are treatment of choice. There has been no general agreement on their optimal dose and duration. High dose corticosteroids (20 mg/kg as a single morning dose with or without maintenance therapy) are associated with a better chance of complete clinical recovery and prevention of relapse. Effective because of their anti-inflammatory and immuno-suppressant effect with an additional effect on cerebral edema. Some studies have reported a favorable response to steroids in terms of better outcome and shortened duration of symptoms. However, studies also report no decrease in long term sequelae with steroids. B. Intravenous Immunoglobulin It has been beneficial when used early in the disease course as well as when used late after failure to respond to steroids. It has shown promising results in relapsing form of ADEMS. C. Glatiramer acetate. D. Polynosine polycytidylic acid polylisine stabilized with carboxymethylcellulose.
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