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Origins of Periodic Limb Movements?

Eric Wassermann ewass at helix.nih.gov
Thu Mar 3 10:29:22 EST 1994

In article <CM2B4L.n1M at freenet.carleton.ca>, aa889 at FreeNet.Carleton.CA (Tim
Kovacs) wrote:
> 	I'm doing an undergraduate thesis on computer quantification
> of electrophysiological phenomena, specifically periodic limb movements
> (PLMs). They are series of limb jerks (resembling the babinski response) which
> occur during sleep. Does anyone know of any theories about the causes of PLM?
> I wouldnt mind some educated geusses...
> Thanks,
> Tim Kovacs
> -- 

The things you kids are doing these days!

These do not resemble Babinski responses which are withdrawal-type
movements of the toes to stimulation of the sole of the foot, so much as
accentuated flexor reflexes in the lower extremities.  To my knowledge
there is no good physiological explanation other than that they are
associated with lighter stages of sleep and drowsiness, occur in some
people while awake, but usually in while sitting or lying, and are very
frequently associated with something called restless leg syndrome which is
a very annoying sense of restlessness, usually in the legs, which also
occurs most often at the end of the day and while lying down.  There is a
strong tendency for all of this to run in families.

Perhaps the most interesting thing about the syndrome is that the best
treatment seems to be drugs that increase dopaminergic transmission, like
L-DOPA and bromocryptine.  These drugs may act in this syndrome by
suppressing the secretion of prolactin by the pituitary gland.  I have been
wondering about this mechanism for a while after seeing several patients
who complained of restless legs with breast feeding and one who developed
the syndrome about the time that a prolactin secreting tumor of the
pituitary was diagnosed.  

A more conventional view would be that the drugs are increasing
dopaminergic activity in the basal ganglia.

I would like to hear how the project goes
                                      As far as I know,
Eric Wassermann                       The opinions expressed are not
Human Motor Control Section           those of the Federal Government,
NINDS, NIH                            the U.S. Public Health Service
                                      or the National Institutes of Health

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