There are many reasons for patients to have dizziness while sleeping on their side, and it may be caused by benign paroxysmal positional vertigo. 1. dizziness can be transient, mostly when patients turn over, and can be relieved significantly if the head position is kept still. 2. if patients sleep on their side and the dizziness does not ease, otoliths are ruled out, and it should be considered to be caused by cervical vertigo. Cervical vertigo is also caused by the patient’s posture, which may cause the patient’s neck to be uncomfortable when sleeping on the side, and for the patient’s vertebral artery, if a continuous compression is formed, the patient will show the symptoms of dizziness. This situation cannot be ruled out because of cerebellar infarction, for example, if the patient has an infarction in the cerebellar region, the dizziness may be aggravated when the patient is in a certain position, and an MRI of the head must be done promptly to clarify.