Blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB) impairment is an additional accident occurring during the amyotrophic lateral sclerosis (ALS) progression. In this work, we aimed to decipher if BBB/BSCB leakage appeared before critical detrimental events and could serve as a marker preceding clinical symptoms. Three different BBB leakage markers: Evans blue, IgG and hemosiderin, were used to look at the SOD1-linked ALS rat model at presymptomatic and symptomatic stages. Although IgG and hemosiderin could be detected at presymptomatic stage, Evans blue extravasation which fits best with BBB/BSCB impairment could only be seen at symptomatic stages. BBB/BSCB impairment was further substantiate by showing at symptomatic stages decreased mRNA expression of ZO-1 and occludin as well as agrin, a basal membrane constituent. Electron microscopic data substantiate a toxic environment around endothelial cell and peri-vascular swollen astrocyte end-feet showing oedema-linked BBB opening.