Alcoholics, elderly, AND elderly-alcoholics are prone to
subdural haemorrhage due to brain atrophy. Alcoholism,
regardless of age, causes pre-mature brain atrophy
thereby increasing the subdural space. Thus, a 55-year
old alcoholic may have brain atrophy that resembles that
of a 75 year old. Atrophy is a natural process with
aging, which explains the increase of subdural space in
the elderly population. Now, if you are elderly AND
alcoholic, the atrophic effects are heightened. This
increase in subdural space allows more room for the
"brain to move around", thus increasing shearing-forces
that may result from mild-trauma, a sudden movement, or
nothing at all (spontaneous). These shearing-forces
cause small bridging-veins (usually subdural bleeds are
venous, but may be arterial) to rupture resulting in the
aforementioned sub-dural bleed. Chronic alcohol use is
very hard on the body and brain...if your patient
appears older than stated age, chances are his/her brain
does too. It is these atrophic changes in the brain that
heighten the chance for chronic/acute/sub-acute
sub-dural bleeds in alcoholics, elderly, AND
elderly-alcoholics.

As for epidural bleeds, I suspect that alcoholics are
more prone than the "normal population", as alcoholics
are more prone to traumatic falls (down stairs, off
curbs, ground level, etc.). Epidural bleeds are almost
always arterial, therefore symptoms are fast and
sudden...these are your walk-and-drop bleeds...why the
text makes it out to sound like epidural bleeds happen
more spontaneously in alcoholics is beyond me...is there
rationale for this claim??

In a side note, I have noticed that alcoholic patients
(usually when they are in their intoxicated state due to
the nature of the ER) seem to have "thin blood"...they
bleed and bleed despite their INR/PTT being normal...I
have never found an answer to this question, but wonder
if it is due to alcohol effects on the liver thereby
inducing coagulopathies? or does alcohol actually have
"blood-thinning" abilities?...has anyone else noticed
this? is there a physiological explanation for this? (or
maybe I really am losing my mind!!)