For the widening of the left lateral ventricle, the reasons are as follows: First, it can be caused by intracranial diseases, such as cerebral infarction or cerebral hemorrhage after the formation of softening foci, resulting in the local brain tissue being stretched, and then there will be widening of the left lateral ventricle. Second, left lateral ventricle widening can be clinically seen in hydrocephalus, especially increased hydrocephalus in the left lateral ventricle, which is mostly caused by obstructive hydrocephalus. Clinically, bilateral lateral ventricular widening is predominant, while simple left lateral ventricular widening and simple left lateral ventricular obstruction are relatively rare. Third, left lateral ventricular widening can be seen clinically in some patients with brain atrophy, due to the atrophy of brain tissue leading to widening of the lateral ventricles, the patient can be accompanied by memory loss, slow reaction, etc., mostly with bilateral widening of the lateral ventricles, can be manifested as the left lateral ventricular widening is more obvious, after the head CT or nuclear magnetic examination can be clear.