27/11/98 21:34
"The world and my body do exist, this is proved by the fact that they gang
up on me to make me suffer."
Jean-Didier Vincent, The Biology of Emotions. (Wonderful work for lay people
dabbling in things neurological.)
Rumaging around on the subject of pain, a subject always close to my
numerous medical abnormalities, I decided perhaps someone can help me
understand this.
Nearly 20 years ago I had a root filling, nerves and pulp removed from a
molar. Prior to this the tooth was usually a little sore due to a poor
filling in the first place circa 4 years prior to the root filling.
To this day I have recurrent pain 'in' that tooth. The pain is similiar to
neuralgic pain: fast and piercing then rapidly subsiding. I currently
understand that neuralgic pain is believed to cause by arterial aggravation
at the root of the 3rd trigeminal nerve. As an aside, I saw this reference
when looking up info for a a friend of mine afflicted with shingles: "The
Message is Clear: Antiherpetics Do Prevent Neuralgia." Modern Medicine, 63;
8 (January 1995). So much for my current understanding!
Pain: not sure if both of the above are 'pain' in the typical sense. The
sensation is very fast and short lived, the neuralgia pain I have
experienced was such that sometimes I would 'duck for cover' (pain at top of
skull, may not be neuralgic but the after effect of extensive and horribly
went wrong neurosurgery) as if avoiding a threatening object. Fortunately
this pain has not visited me for a few years and in any event it was more a
curiousity than a problem. I suppose that's one way to deal with it.
Thinking of phantom limbs and the like, I am curious as to the source for
this dental pain. The peri-aqueductal gray matter\thalamic\neocortical?
The other possibility to consider here, consistent perhaps with the above
explanation of neuralgic pain, is that the severed nerve is still being
aggravated just under the tooth, my poor old brain not picking the
difference, though to be sure sometimes I think it feels like this current
pain is under the tooth; even moreso if I think about it ... . The problem I
have with this explanation is that I can't see that the nerve root would
have survived through such a trauma.
In another post on this ng the question of muscle rigidity from lack of
inhibitory regulation via the brainstem was mentioned. This parallels with
experiments showing how stimulation of the periaqueductal area in rats
stopped them flinching when tails pinched, the idea being that within the
brainstem there exists some type of regulatory inhibitory system that finds
activation probably only in flight or fight situations. In Vincent's text he
makes reference to the inhibitory influence of the raphe nucleus, a region
rich in serotonin producing cells. Could it be that prolonged low level pain
has the effect of shutting down the usual inhibitory activity?
At a rather large reach I wonder if this correlates with post traumatic
stress disorder, some research indicating that this could be the result of
hippocampal damage through over production of cortisol destroying one route
through which we manage stressful situations. Feel free to take aim at this.
Another issue here is whether or not pain should be deemed the sixth sense.
Are there sufficient neuroanatomical consistencies with the other senses to
include it in this scheme? Eg. All sensory inputs are subject to inhibitory
guidance from the brainstem upwards, senses inform us about the world, and
if my limited understanding is correct it appears that pain, like the other
senses, goes through a number of junctions and processing levels all the way
to the neocortex. Is there something unique about pain that precludes it
being a sense like hearing, smell, vision, touch, and taste? Or is that we
just live in a culture with the vestiges of atavistic Calvinist morals?
Thanx
John
The meaning of life is that it stops.
Franz Kafka
