Table 1.

Comparative pathology of the demyelinative lesions in acute disseminated encephalomyelitis (ADEM) and multiple sclerosis (MS)

Pathological characteristics	ADEM	Acute and chronic MS
Distribution	Focal, regional or diffuse	Multifocal; as a rule entire central nervous system is affected in chronic MS
Age of lesions	Always same and uniform	Always of different ages (both in acute and chronic MS)
Size of lesions	0.1–1.0 mm	1.0 mm or less to 5+ cm
Relation of lesions to:
Veins	Always	Prominent and usual
Pia	Usual	Rare
Degeneration of:
Axis cylinders	Mild to severe	Mild to moderate
Nerve cells	Mild	Mild to moderate
Oligodendroglia	Restricted to lesions	Restricted to lesions
Astrocytosis	Mild	Marked in chronic MS
Tissue necrosis	May be severe	Rarely severe
Perivascular infiltration	Always and marked	Usually (but not always) present; prominent only in acute MS
Meningeal inflammation	Minimal to pronounced	None
Vascular damage and fibrin deposition	Constant and severe in hyperacute cases	Mild or none
Microglial proliferation	Marked, with pleomorphic forms	Pleomorphic forms in acute cases