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Winning Abstracts from the 2008 Medical Student Abstract Competition: Acute Disseminated Encephalomyelitis Presenting Without Clinical Encephalitis

Author: Sheena Sahota, University of Missouri, Kansas City

Introduction
Acute disseminated encephalomyelitis (ADEM) is a nonvasculitic demyelinating disease diagnosed by clinical signs of encephalitis and myelitis with corresponding MRI findings on brain and spinal cord. We report a patient who presented with myelitis, but no clinical signs or symptoms of encephalitis, while MRI brain and spine showed hyperintensities on T2/FLAIR which later resolved on follow up imaging. The MRI demonstrated reversible lesions in both brain and spinal cord.

Case Presentation
A 50 year old male presented with acute onset of urinary retention, low grade fever, followed by bilateral lower extremity weakness one month after his flu vaccination. Examination demonstrated flaccid paraparesis with decreased rectal tone and sensory loss below the T3 dermatone. MRI T2 images with no contrast enhancement were done of the cervical and thoracic spinal cord and showed multi-focal high intensity signals in the anterior and central cord. FLAIR images were seen in both white and grey matter that did not enhance on T1. No flow voids or cord swelling were seen. Diffusion weighted MR showed no restricted diffusion. CSF analysis was remarkable for lymphocytic pleocytosis and elevated protein. Workup for infectious and toxic causes were negative. Patient was treated with IV steroids for presumptive diagnosis of ADEM and showed marked clinical improvement. Repeat MRI showed resolution of signal changes in brain and spinal cord. He was subsequently discharged to inpatient rehabilitation.

Discussion
ADEM is an immune-mediated inflammatory disorder characterized by extensive, multifocal, subcortical demyelinating lesions throughout the central nervous system on MRI. Neuromyelitis optica (NMO), multiple sclerosis, and acute transverse myelitis (ATM) are hallmark demyelinating diseases; the first two of which have characteristic brain imaging abnormalities. This patient presented with acute onset myelitis with no features of encephalopathy iterating the fact that brain lesions in ADEM can be present without clinical findings. Our patient had unremarkable infectious workup and his MRI lesions reversed after steroid therapy making ADEM more likely diagnosis. Transverse myelitis alone could explain his symptoms, but identification of an encephalitis component in ATM, if found, gives credence to the hypothesis that this disease entity is actually a subset of ADEM or a part of continuum of neuroimmunological demyelinting disorders including NMO and ADEM.

ADEM by iself has favorable prognostic outcomes as compared to other etiologies of myelitis because it is reversible. The need for developing diagnostic criteria for ADEM and the question of if brain imaging should be done in all patients who present with transverse myelitis is one that must be answered.

Back to August 2008 Issue of IMpact

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