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NEURORADIOLOGY Table of Contents   
Year : 2006  |  Volume : 16  |  Issue : 4  |  Page : 739-741
Acute disseminated encephalomyelitis - a case report


Department Of Radiodiagnosis, Pt. B.D. Sharma Post Graduate Sharma Institute Of Medical Sciences Rohtak-124001, Haryana, India

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Date of Submission28-Feb-2006
Date of Acceptance10-Aug-2006
 

Keywords: Acute disseminated Encephalomyelitis, Perivenular demyelination, Monophasic , Multiple Sclerosis, Magnetic Resonance Imaging

How to cite this article:
Yadav R K, Agarwal S, Richa. Acute disseminated encephalomyelitis - a case report. Indian J Radiol Imaging 2006;16:739-41

How to cite this URL:
Yadav R K, Agarwal S, Richa. Acute disseminated encephalomyelitis - a case report. Indian J Radiol Imaging [serial online] 2006 [cited 2019 Aug 24];16:739-41. Available from: http://www.ijri.org/text.asp?2006/16/4/739/32336

   Introduction Top


Acute Dissemiated Encephalomyelitis (ADEM) is an uncommon inflammatory infection mediated demyelinating disease. It's true incidence is unknown, however it occurs predominantly in children. Pathologically it is thought to result from transient autoimmune response towards myelin or other self antigens. It is monophasic & occurs following infections after a latent period of approximately 2 weeks. On Cerebro-Spinal Fluid ( CSF ) there may be moderate pleocytosis with increased protein contents. Other investigations are generally normal. Magnetic Resonance Imaging( MRI ) is the modality of choice.


   Case Report Top


A seven months male child presented with complaints of cough, nasal discharge & fever of seven days duration along with multiple cervical lymphnodes for which he was treated conservatively. Routine hematological investigations and chest X-Ray were normal at this time. Thereafter patient presented with seizures following a latent period of 15 days. There was no relevant past history. He had received all vaccines relevant for his age.

Systemic examination was normal. Central Nervous System (CNS) examination was also normal with normal pupillary and corneal reflexes and no meningeal signs. CSF on examination was clear, Proteins were 55mg%, Sugar was 68mg/ dl and on Gram staining there were 6-8 RBCs per high power field. EEG revealed diffuse slow wave discharge in theta range. Fundus examination was normal.

Computed Tomography (CT) of Brain was normal. MRI was performed on 1.5 Tesla magnetom Harmony unit (Philips, Gyroscan Intera model). Routine unenhanced spin-echo T1W (TR/TE - 596,15), T2W (4858,110) & T2W FLAIR (6000/120) sequences were obtained in multiple planes. Single shot EPI Diffusion sequence was obtained in oblique axial planes in three directions with b value of 100, followed by isotropic image acquisition & ADC maps. There were multiple subcentimeter foci hypointense on T1W images & hyperintense on T2W & Diffusion weighted images located asymmetrically in subcortical region of bilateral frontal, parietal & occipital lobes. On T2W FLAIR images the lesions were not well defined & were hypointense. These revealed variable enhancement on contrast enhanced images and showed no mass effect. No evidence of any meningeal enhancement was noted.

Basal ganglia & Internal Capsules were normal. Ventricular system, basal cisterns & other posterior fossa structures were normal.

Patient was treated with high dose intravenous methyl prednisolone with improvement.


   Discussion Top


ADEM is an uncommon inflammatory demyelinating disease of the CNS & can be defined as scattered focal or multifocal inflammation of the Brain &/ or the spinal cord[1] .The true incidence of ADEM is unknown & in India the disease is surely more frequent than reported. As would be expected from an infection mediated syndrome ADEM most commonly presents during winter & spring[2],[3]. Between 51% & 74% of ADEM patients have an incidence of precipitating infection with a mean latency of approximately 2 weeks[2],[3],[4],[5]. A large no. of infections may precipitate ADEM, although isolation of specific agent is uncommon (classic infection precipitants include measles, Ebstein barr virus, mycoplasma & Group A streptococcus). Multiple sclerosis (MS) is it's main differential diagnosis. Although infection may precipitate multiple sclerosis relapse the association with infection & seasonality is less pronounced. In contrast to multiple sclerosis ADEM is usually a monophasic disorder with favorable long term prognosis.

Pathogenesis of ADEM is thought to result from a transient autoimmune response towards myelin or other self antigens via molecular mimicry, or by non-specific activation of auto reactive T-cell clones.

On histopathology there is inflammation predominantly in the Virchow-Robin spaces & diffuse often asymmetric perivenular demyelination. The lesions are of similar histological age & more numerous in white matter but often involve the deep cortical lamina, thalami, hypothalamus & other gray matter structures.

Monophasic ADEM is more common in children whereas multiple sclerosis is more common in adults. Mikaeloff et al showed a mean age of 7.1 years & 12 years in paediatric ADEM & multiple sclerosis patients respectively[6]. Most series of ADEM have failed to show a sex predominance although some series show a mild male predominance[2],[4],[6]. By contrast females are more prone to develop multiple sclerosis particularly in adolescence & adulthood6. It can occur at any age, but more common in children because of higher frequency of immunization & exposure to antigens. The onset of symptoms is preceded by a prodromal phase of several days of fever, malaise & myalgia. Clinical features include multifocal neurological disturbances such as bilateral optic neuritis, visual field defects, aphasia, sensory & motor deficits, ataxia, movement disorders & signs of an acute meningoencephalopathy with meningism such as depressed level of consciousness, focal or generalized seizures & psychosis.

Lab evaluation reveals that CSF is abnormal in 67% of patients and usually demonstrates increased pressure, proteins & white & red cells[5],[8]. CSF only rarely shows intrathecal oligoclonal immunoglobulin (IgG) which invariably ceases as patients improve. Electroencephalogram abnormalities are common but nonspecific[5],[7].

CT is usually normal at onset & later shows low attenuation multifocal lesions in subcortical white matter. MRI is the premier modality of choice in the diagnosis of ADEM. Pathological correlation in experimental allergic encephalitis has shown long T1 & T2 values to be associated with presence of inflammation, demyelination & haemorrhagic necrosis. The lesions in ADEM often have poorly defined margins2-5 & are usually located in the peripheral subcortical cerebral white matter. The lesions in Thalami are more often described in ADEM than multiple sclerosis & may be a useful finding that suggests ADEM. Lesions in Internal capsule have low sensitivity in MS. Tumor like lesions have also been described In MRI of ADEM patients8. Usually all the lesions enhance with contrast, but in some patients there may be enhancement of some lesions without enhancement of others. this is because the lesions in ADEM may evolve over several weeks8. When the spinal cord is involved the lesion is typically large, swollen & thoracic. By contrast lesions in Multiple sclerosis which is more common in adults are small, have well-defined plaque like margins & tend to be in periaqueductal region, Corpus Callosum & periventricular white matter. The spinal cord lesions in MS are typically smaller, more discrete & cervical. Follow up MRI is useful in ADEM & MS differentiation. As expected new lesions should not occur in ADEM[2],[3],[4] & original lesions completely resolve in 27-55% of cases. By contrast new lesion in MS are anticipated. A lag time of 6 months after presentation would be appropriate for repeat scanning (when clinically indicated).

In the absence of biological marker the distinction between ADEM & MS cannot be made with certainty, at time of first presentation, however a viral prodrome, early onset ataxia, high lesion load on MRI involvement of deep Gray matter & Thalami & absence of oligoclonal bands are more indicative of ADEM[5].

Spontaneous improvement has been repeatedly noted in ADEM, however complete recovery is less frequently seen in patients not receiving some form of treatment. High dose steroids (intravenous methyl prednisolone) has been found to be effective. If high dose steroids fail it is reasonable to advice plasmapheresis7 which if initiated early in a patient with preserved reflexes especially in a male is associated with moderate & marked improvement. Intravenous immunoglobulin is third potential therapeutic modality.

Poor prognostic indicators include prolonged disturbances in levels of consciousness, multiple or extensive lesions on MRI. Acute Hemorrhagic leucoencephalomyelitis (AHLE) is associated with fatal outcome. Prognosis is also related to antecedent factors. Complete recovery occurs in 50% & mortality rate is 10-30%.

 
   References Top

1.Alvord BC Jr: Demyelinating diseases: In: Handbook of clinical neurology, Vinken PJ, Bruyen GW,eds. Elsevier Publisher BV, Amsterdam. 1985; 3 : 467- 502.  Back to cited text no. 1    
2.Dale RC, de Sousa C, Chong WK, et al: Acute disseminated encephalomyelitis, multiphasic disseminated encephalitis & multiple sclerosis in children. Brain 2000; 123(12): 2407-22.  Back to cited text no. 2    
3.Murthy SN, Faden HS, Cohen ME, et al: Acute Disseminated Encephalomyelitis in children. Pediatrics 2002; 110(2) : e21.  Back to cited text no. 3    
4.Tenembaum S, Chamoles N, Fejerman N: Acute disseminated encephalomyelitis: A long- term follow-up study of 84 paediatric patients. Neurology 2002; 59: 1224-31.  Back to cited text no. 4    
5.Hynson JL, Kornberg AJ, Coleman LT, et al: Clinical & Neuroradioloic features of acute disseminated encephalomyelitis in children. Neurology 2001; 56: 1308-12.  Back to cited text no. 5    
6.Mikaeloff Y, Suissa S, Vallee L et al. First episode of acute CNS inflammatory demyelination in childhood; Prognostic factors for multiple sclerosis & disability. JPediatr 2004; 144 : 246-52.  Back to cited text no. 6    
7.Schwaz S, Mohar A, Knauth M, et al. Acute Disseminated Encephalomyelitis : A follow up study of 40 patients . Neurology 2001; 56: 1383-88.  Back to cited text no. 7    
8.Murthy JM: Acute Disseminated encephalomyelitis. Neurol India 2002; 50: 238-43.  Back to cited text no. 8    

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Correspondence Address:
S Agarwal
DNB Lecturer, 60 L, Model Town, Rohtak-124001 Haryana
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-3026.32336

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    Introduction
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    References
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