My husband has Lewy Body Dementia. You can find excellent information at lbda.org, the website for the Lewy Body Dementia Association. We also have a members-only online support group for spouses of people with LBD. You can request membership at http://groups.yahoo.com/group/LBD_caringspouses/.
LBD is often undiagnosed and misdiagnosed, so you need to find a geriatrician or neurologist who is very familiar with LBD. There are several markers for LBD, but not every person will have them all: fluctuating cognition, gait and balance problems, hallucinations, delusions, neuroleptic sensitivity, REM sleep disturbances, compromised autonomic functions.
We also have an extensive set of resources on the Caring Spouses site with articles and links to websites about LBD.