[Neurological manifestations of Behçet's disease].

Neurological manifestations of Behçet's disease (BD) occur in 5.3 to more than 50% of patients. They are divided into two major forms: "parenchymal" lesions, which include mainly meningoencephalitis as opposed to "extra-parenchymal" lesions (i.e. cerebral venous thrombosis and arterial aneurysms). Myelitis or peripheral neuropathy is exceptional. The neuro-Behçet syndrome (NBS) should be considered in the setting of neurological manifestations, particularly headache and pyramidal signs, in a young man diagnosed with BD. However, its recognition may be difficult when neurological manifestations are the presenting features of BD (one third of cases), and requires a thorough knowledge of clinical manifestations and morphological lesions. Thus, parenchymal NB lesions classically exhibit inflammatory characteristics on MRI and are located at the meso-diencephalic junction and in the brainstem, rarely with a supratentorial extension. Meningitis is not systematically associated, and may be absent in about 30% of cases. The pathogenesis of these lesions is incompletely understood, but inflammatory infiltrates include mainly neutrophils and activated T cells (mainly Th17). Differential diagnoses include infectious diseases (herpes, listeria, tuberculosis), and inflammatory diseases (i.e. multiple sclerosis and sarcoidosis). A prompt recognition of NBS should lead to initiate adequate therapies in order to limit the risk of sequelae, relapses or death.