Brian Collins wrote:
>As you
> probably know, you are down to the last 20% of your
Dopamine-producing cells
> when the symptoms show,
This is a statistic that those of us who have been around the traps
for a while take as a given. I have always seen it expressed much
the way Brian does above (and indeed have used almost identical
wording myself on numerous occasions) but reading it today I suddenly
realised that I don't know exactly what is meant by it.
Does it mean we are down to 20% at the time we are diagnosed (surely
the earliest opportunity for anyone to start measuring) or as
actually stated does the 20% relate to our earliest symptoms which in
many anecdotal cases seem to predate diagnosis by between 6 to 10
years.
Which raises the question of how this figure is arrived at. As I
understand things, even the most sophisticated modern equipement
cannot reproduce the interior of the head in suffecient detail to
show the status of the substatia nigra. So presumably the figure was
reached by some form of extrapolation based on post mortum data. As
the date of diagnosis is the only firm date that a researcher would
have for onset of symptoms, it seems likely to me that this is the
date to which the 20% applies.
This implies, to me at least, the following.
1. If the 20% relates to true onset of symptoms.
By the time a diagnosis is made the substatia nigra will have been
reduced even more than 80%. The exact figure will vary from
individual to individual depending on how late in the process they
are diagnosed. This discrepency alone would go some way to
explaining why PWP experience such varied periods of time before
encountering some of the complications of dopamine replacement meds.
2. If the 20% relates to the time of diagnosis.
This would imply that the substantia nigra is reduced by 80% before
the symptoms are suffeciently established for a diagnosis to be made.
If this is the case it means that symptoms start to appear after the
loss of a smaller (yet to be established) % of the substantia nigra.
Which would appear to shift the baseline.
I trust that this apparant vagueness only occurs in layman's versions
of the literature and that researchers have things a little more
pinned down. If anyone has this information I would appreciate being
enlightened.
Thanks,
Dennis.
**************************************************
Dennis Greene 48/11
[log in to unmask]
http://members.networx.net.au/~dennisg/
**************************************************
