The pathogenesis of cervical artery dissection is poorly understood. Deficiency of the elastase inhibitor alpha-1-antitrypsin may represent a predisposing condition. Biochemical and genetic analyses in a series of 12 consecutive patients with spontaneous dissection of the neck vessels showed 3 cases associated to alpha-1-antitrypsin deficiency, in combination with transient precipitating factors. A disequilibrium between proteolytic enzymes and protease inhibitors may contribute to the pathogenesis of cervical artery dissection leading to structural abnormalities of the extracellular matrix and increasing the susceptibility of the vessel wall to additional short-lived trigger mechanisms.