L. Levin, M.D. pathdoc@...>: Re: RLS: nerves, Dr. Levin

[Guest guest]

Someone asked for the message from Dr. Levin on nerves, here it is, I

forgot who requested it so am posting it to the group again....

Debbie

Jill Gunzel wrote:

>

>

>

> Dr. Levin...

> Could you please take it a step further? You wrote: " The abnormalities

of

> RLS are felt to be in the spinal cord and/or the brain, not the

nerves. "

>

> I don't know about other people, but I think I assume " nerves " when I

think

> of spinal cord and/or brain. " What am I missing, here? I'm guessing

you

> mean that RLS is associated with nerve problems in the spinal cord and

> brain, as opposed to something like nerve entrapment in my big toe

(which

Jill

Anatomically, the human nervous system is divided into two parts, the

central nervous system and the peripheral nervous system. The CNS is

composed of the brain and spinal cord. The PNS is composed of the

cranial and spinal nerves. The nerves in the extremities are spinal

nerves. The cell bodies for the peripheral nerves reside in the brain

or the spinal cord. The peripheral nerves are cytoplasmic extensions

of these cell bodies. Diseases that affect the brain are called

encephalopathies, diseases that affect the spinal cord are

myelopathies and diseases that affect the peripheral nerves are called

neuropathies. Different diseases have a predilection for different

parts of the nervous system. The current evidence is that the

abnormalities in RLS reside in the CNS not the PNS. Neuropathies can

be the cause for secondary RLS but the abnormality that actually

causes the RLS is still within the CNS (brain and/or spinal cord).

What you are considering nerves in the spinal cord and brain are

called " tracts " . These consist of large bundles of nerve fibers which

are immediately adjacent to and not physically separated from other

bundles of nerve fibers. These fibers do not form " nerves " until they

leave the CNS. At that point, they are structurally and metabolically

different than their counterparts in the CNS. This is probably why

they are affected by a different set of diseases than their CNS

counterparts. Think of the PNS as transmission lines. The messages

that they carry originate in the CNS.

I hope this clears up the confusion.

Dr. Levin

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