[Chiasmatic syndrome].

The optic chiasm is an essential anatomical structure in neuro-ophthalmology. The systematization of the visual pathways results from the arrangement of the retinal ganglion cell fibers. It explains the signs of chiasmal syndrome. A good knowledge of the anatomy permits to correlate visual field defects with imaging results. It is now possible to map the organization of the ganglion cell fibers within the chiasm. Their hemidecussation allows for stereoscopic vision in humans. The causes of chiasmal syndrome are multiple, but tumors and compressive causes predominate. The proximity of the pituitary region to the chiasm accounts for the frequency of chiasmal syndrome, which involves ophthalmologists not only through dysfunction of the visual pathway, which may be the presenting sign, but also through possible complications throughout the course of the disease. This review aims to synthesize the embryology, anatomy and principles of work-up for chiasmal syndrome as well as its many possible causes.