The sudden appearance of crooked mouth in the elderly may be due to peripheral facial palsy or central facial palsy, as follows: 1. Peripheral facial palsy: refers to facial nerve paralysis, which is often caused by viral infection or damage to the facial nerve caused by cold, etc. Patients will show a shallow nasolabial folds, shallow frontal lines, and crooked corners of the mouth, but there will be no other symptoms of neurological deficits; 2, Central facial palsy: caused by vascular diseases of the brain, such as cerebral infarction or minor cerebral hemorrhage. In addition to crooked mouth, the patient may also have a tongue that is not centered when extending the tongue, and may deviate to the left or to the right, and may be accompanied by other symptoms of neurological deficits, such as numbness and weakness in one of the limbs, or dizziness, clumsy speech, visual field deficits, etc.