Dysarthria

Dysarthria is a motor speech disorder which affects the musculature and systems needed for producing speech. Individuals with dysarthria may exhibit too much muscle tone or too little. Muscles may be weak, paralyzed, or uncoordinated. Speech is slurred or is hard to understand. Dysarthria may affect systems of respiration, phonation, resonance, articulation, and prosody.  Dysarthria affects children and adults. Conditions that can cause dysarthria are:  stroke, traumatic brain injury, cerebral palsy, and multiple sclerosis.
(Reference: The Source for Dysarthria by Nancy B. Swigert)

http://www.asha.org/public/speech/disorders/dysarthria.htm
http://www.kidspeech.com/index.php?option=com_content&view=article&id=216&Itemid=502
http://www.playingwithwords365.com/2011/10/speech-motor-speech-disorders-dysarthria/