Dysarthria often is characterized by slurred or slow speech that can be difficult to understand. Common causes of dysarthria include nervous system (neurological) disorders such as stroke, brain injury, brain tumors, and conditions that cause facial paralysis or tongue or throat muscle weakness.Certain medications also can cause dysarthria.ysarthria treatment is directed at treating the underlying cause of your condition when possible, which may improve your speech. You may have speech therapy to help improve speech. For dysarthria caused by prescription medications, changing or discontinuing the medications may help. 1  Symptoms.