Cyclic alterations of Spinal Excitability in patients with Perodic Limb Movements during Sleep and Restless Legs

The Restless Legs Syndrome (RLS) is a disorder of the central nervous system,
leading to complaints of dysesthesia or paresthesia in the legs or, less often,
in the arms. Typically, complaints occur in the evening and can be relieved by
movement of the affected limbs.
In approximately 80% of the patients with RLS, periodic leg movements occur
during sleep (PLMS). These muscle contractions last for 0.5 to 5 seconds and
are repeated every 20 to 30 seconds. These movements often lead to some
arrousal and may therefore cause complaints of excessive daytime sleepiness.
Since both RLS, sensory complaints during wake, and PLMS, a motor phenomenon
during sleep, share a distinct periodic character, they are possibly caused by
cyclic suppresion of spinal excitability.

The aim of this study is to seek evidence that such cyclic suppression exists.
For this purpose, we will use the Hoffmann- or H-reflex, an electrically evoked
reflex. By stimulating the tibial nerve in the knee, the alpha motor neuron in
the spinal cord is activated. This motor neuron sends a signal back, causing
contraction of the calf, which can be measured by electromyography (EMG). The
amplitude of this signal is the resultant of exciting and inhibiting influences
on the alpha motor neuron in the spinal cord. Therefore, cyclic changes in
spinal excitability are reflected in the amplitude of the H-reflex.

Prospective observational study

Stopping all medication influencing RLS and/or PLMS two weeks prior to the
study may lead to an increase in complaints, but this will not cause any damage
tot the patients' health. Furthermore, this increase in complaints is
completely reversible when medication is restarted. All used registration
methods, the H-reflex as well as sleep registration techniques, have been used
worldwide for decades and are completely safe.