Delayed speech with heaviness and numbness in the tongue can all lead to slurred speech
or dysarthria. Dysarthria refers to slow and distorted speech
, such as slurring. It results from the inability to control or coordinate the muscles used in speaking. It could be caused due to traumatic head injury, stroke, bell’s palsy, degenerative diseases of the brain etc.
I think in your mother’s case it could most probably be stroke or bell’s palsy.