Here is some basic info:

http://www.brain.northwestern.edu/mdad/frontal.html

Essentially, its a progressive dementia, and didn't used to be
differentiated from AD by most doctors, but needs to be, since the
drugs used to treat AD can actually make it worse. Frontal lobe
dementia is the name given to any dementia caused by damage to that
part of the brain - a common type is called Pick's disease.

Since the frontal lobe is the part of the brain that governs mood,
behaviour, judgement and self control, you can imagine what the
symptoms look like. Rather than memory issues, the first signs are more
often alterations in personality and behaviour, changes in the way a
person feels and expresses emotion, and loss of judgement.

It often hits people in middle age, who suddenly start behaving in
strange ways - becoming rude and insensitive, uninhibited, obsessive.
They also have language problems early in the game. The personality
changes can really be bewildering - the person seems cognitively
intact, but starts doing socially inappropriate things, like making
rude comments in public, being overtly sexual, playing practical jokes,
being totally uninhibited (scratching, disrobing). They tend to have
language problems early and also tend to put things in their mouth a
lot, and can get into eating obsessively (plus eating strange things).
And...they are often roamers.

So, its a different behaviour profile. They tend not to have the memory
and reasoning problems until later in the game - although the fact that
they SEEM with it can make their strange behaviour really hard to
fathom. They also tend not to have the muscular coordination problems
as early.

In the end, they arrive at the same place as someone with end stage AD.

I think it would be really hard to deal with i.e. your formerly kind
and reasonable 55 year old spouse who SEEMS normal in terms of memory
and mental abilities suddenly starts acting like a jerk, gets fired
from his job for grabbing the secretary and being rude at meetings,
starts drinking and eating obsessively etc.

Its often mistaken for mental illness in the early stages for obvious
reasons.

Mary G.