Dysarthria occurs when the muscles you use for speech are weak or you have difficulty controlling them. Dysarthria often causes slurred or slow speech that can be difficult to understand. slurred, nasal sounding or breathy speech. a strained and hoarse voice. very loud or quiet speech. problems speaking in a regular rhythm, with frequent hesitations. There are several types of Flaccid dysarthria—from damage of the cranial nerves or regions of the brainstem and midbrain. Spastic dysarthria—from damage to the motor regions in the cortex, on both sides of the brain. Dysarthria caused by medicines or poorly fitting dentures can be reversed. Dysarthria caused by a stroke or brain injury will not get worse, and may improve. Dysarthria after surgery to the tongue or voice box should not get worse, and may improve with therapy. Common causes of dysarthria include nervous system disorders and conditions that cause facial paralysis or tongue or throat muscle weakness. Certain medications also can cause dysarthria.