Voluntary motor activity in Restless Legs Syndrome and Periodic Limb Movements in Sleep

Periodic Limb Movements during Sleep (PLMS) are repetitive, stereotypic, and
involuntary dorsiflexion movements of the lower limbs during sleep. These
movements can be monitored by electromyographic registration of leg movements
during a sleep study (polysomnography). These movements are present in more
than 30% of adults over 60 years of age. Periodic Limb Movement Disorder (PLMD)
is the combination of PLMS and insomnia or excessive daytime sleepiness (not
otherwise explained). The prevalence of PLMD is not known.

Similar Periodic Limb Movements (PLM) are very common in patients with Restless
Legs Syndrome (RLS). RLS is a common neurologic disorder characterized by an
irresistible urge to move the legs. The four essential criteria for the
diagnosis of RLS are undesirable sensations in the legs that occur before sleep
onset; an irresistible urge to move the limbs; partial or complete relief of
the symptoms on movement of the limbs and return of symptoms on cessation of
the movements. These symptoms may disrupt sleep. The prevalence of RLS has been
estimated to be 10-15% in the general adult European population.

Because of the clinical similarities between RLS and PLMS these terms are often
used interchangeably. However only 30% or less of patients with PLMS have RLS.

Untill now, only few studies have been performed to investigate the differences
between RLS and PLMS.

The aim of this study is to investigate the differences between RLS and PLMS.

Prospective observational case control study.

RLS and PLMS patients will visit the department of neurology of the UMCG twice.
The first visit will consist of history taking and (neurologic) physical
examination. Afterwards the sleep study (polysomnography, PSG) will be
performed. PSG is a noninvasive recording of the biophysiological changes that
occur during sleep. The PSG monitors body functions including brain, eye
movements, skeletal muscle activation (the PLM) and respiratory effort. Subject
sleep at home.
During the second visit the next day, the PSG equipment will be detached,
followed by the manipulandum test and TMS.
The manipulandum test is an noninvasive study of the fine motor activity.
Participants will held a joystick and have to perform a circular tracking task.
TMS uses a rapidly changing magnetic field to activate the primary motor
cortex. This produces muscle activity which can be recorded on
electromyography. The most serious complication of TMS is the rare occurrence
of seizures. However, this risk is very low and TMS is worldwide considered a
safe procedure. Moreover subjects with a tendency for epileptic insults will be
excluded.
Peripheral nerve stimulation and electromyographic recordings are standard
neurophysiologic examinations and without specific risks.

The control subjects will pay one extra visit for performing actigraphy.
Actigrafy is a noninvasive method (a watch-shaped instrument worn on the ankle)
for screening for PLM. Controls with an high index for PLM on the actigraphy
will be excluded.

Secondarily RLS patients without PLM will be studied. They will pay one extra
visit for performing actigraphy as well as the control subjects.

There is no direct benefit for partcipants.