When people speak it requires considerable coordination of a large number of facial and related muscles. Your speech may slur because the normal muscular control of voice production has failed through weakness, or because the muscles are not operating in the right sequence. As a result your speech may sound slurred or be uncoordinated. ‘Dysarthria’ is the name given to general problems like this and may be associated with several neurological diseases. Sometimes your speech will just sound slightly slurred, but still be intelligible to others, but with more serious problems of coordination it may be difficult for others to understand you.