Assuming his dilantin levels are normal, I suspect it is his stroke. Stopping his drugs for a day or so may help differentiate between drug effects and his stroke. First, clear this with his doctor.
http://www.druginfonet.com/index.php?pageID=faq/new/DRU...
Dysarthria is motor speech disorder affecting muscles of mouth, face, & respiratory system. They may become weak or move slowly.
http://www.chacha.com/question/is-there-a-such-thing-as...
Many people with dysarthric speech are able to use the DragonDictate voice recognition system. This is available from Words Worldwide.
http://www.wordsworldwide.co.uk/faq.php
1. impaired articulatory ability resulting from defects in the peripheral motor nerves or in the speech musculature
http://www.audioenglish.net/dictionary/dysarthria.htm
・ 1 Carry on a normal conversation with the person. ・ 2 Notice which problems and disfluencies they display. Don't categorize anything, yet. You may miss an... ・ 3 Check for "receptive" (auditory) understanding by asking the perso...
http://www.ehow.com/how_2052159.html?ref=Track2&utm_sou...
Dysarthria is caused by poor control of the speech muscles. Damage to the brain or the nerves that control the muscles involved in speaking can cause weakness, slowness and inco-ordination of the speech muscles. It may be the result of stro...
http://neurology.health-cares.net/dysarthria-causes.php
Reduced speech intelligibility may be caused by symptoms associated with any of the following processes of speech.
http://www.utmedicalcenter.org/news/Dysarthria/928.html