**Abstract**

The objective of this article is to investigate the link between chronic inflammatory bowel disease (IBD) and central nervous system (CNS) demyelination. CNS demyelinating disorders in IBD are rare complications and are due to a dysimmune mechanism. We report the clinical cases of two patients followed for IBD. The first patient had Crohn's disease for 12 years and developed acute disseminated encephalomyelitis (ADEM) 1 month after the first course of the anti-tumor necrosis factor alpha (anti-TNF-alpha), infliximab. The second patient, treated for ulcerative colitis with salazopyrin, developed multiple sclerosis (MS) 5 months after the start of her disease. MS and optic neuritis remain the inflammatory demyelinating diseases of the CNS most frequently associated with IBD. The activation of T lymphocytes during IBD plays an essential role in the pathogenesis of MS and ADEM in a genetically predisposed population. It is currently recommended that patients with IBD be evaluated clinically and by MRI for subclinical demyelinating lesions in order to guide therapeutic management.

**Keywords:** chronic inflammatory bowel diseases, multiple sclerosis, encephalomyelitis
