Vertebrobasilar insufficiency (VBI) refers to a condition characterized by reduced blood flow within the vertebrobasilar arterial system, which supplies the posterior regions of the brain including the brainstem, cerebellum, and occipital lobes. Insufficient perfusion in this vascular territory may lead to transient ischemic symptoms or permanent neurological deficits. Clinical manifestations commonly include vertigo, dizziness, visual disturbances, ataxia, and syncope. The most frequent underlying causes include atherosclerotic stenosis, arterial dissection, and mechanical compression of the vertebral arteries. Because symptoms are often nonspecific, accurate diagnosis requires careful clinical assessment combined with vascular imaging techniques to evaluate posterior circulation hemodynamics and structural abnormalities.