Heterogeneity in clinical presentation of acute disseminated encephalomyelitis (ADEM)

Sudhir Kumar, M Alexander, C Gnanamuthu 
 Neurology Unit, Department of Neurological Sciences, Christian Medical College, Vellore, Tamil Nadu - 632004, India

Correspondence Address:
Sudhir Kumar
Neurology Unit, Department of Neurological Sciences, Christian Medical College, Vellore, Tamil Nadu - 632004
India

Full Text

Sir,

Acute disseminated encephalomyelitis (ADEM) refers to a monophasic, immune-mediated, inflammatory demyelinating disease of the central nervous system, predominantly affecting the white matter. Though ADEM was first reported more than 70 years ago[1] and the term is widely used today, it seems to be inadequate in the light of increasing clinical experience with ADEM. The current communication is aimed at highlighting the clinical heterogeneity of ADEM and the need for a more suitable term for this syndrome.

The term "disseminated" refers to the involvement of multiple sites of neuraxis, either clinically or subclinically (when identified with the help of neuroimaging or multi-mode evoked potential studies in the absence of symptoms/signs). However, "focal or site-restricted forms" of ADEM are well known. Cases presenting with optic neuritis or myelitis alone have been reported.[2] Solitary hemispheric lesions mimicking tumors have also been reported.[3] Therefore, the term "disseminated" is not appropriate for all cases of ADEM.

The term "encephalomyelitis" is non-specific as it means inflammation of the brain and spinal cord indicating that the entire central nervous system is involved. However, many cases of ADEM do not have such a diffuse involvement and manifest with lesser degrees of involvement.

The term ADEM (a post-infectious or post-vaccinial illness) does not indicate the etiology and therefore does not help in the differentiation of infectious (viral) or allergic encephalomyelitis. In addition, it does not convey the fact that ADEM is a monophasic illness (as against multiple sclerosis which is recurrent in nature).

These observations point to the fact that ADEM is a term that is not appropriate for many patients diagnosed with it. There is a need to substitute it with a better term. "Monophasic immune-mediated central nervous system demyelination" is one suggestion from us.

References