Supportive features

Three factors help to support a diagnosis based on the four essential criteria. These are:

1. Dopaminergic responsiveness The dopamine system within the brain is thought to play a role in the mechanism that underlies RLS. Many patients with RLS notice an improvement in their symptoms when they take drugs that boost the dopamine system.

2. Periodic limb movements during sleep (PLMS) (in individuals under 50 years of age).

* Individuals of any age may experience periodic limb movements during wakefulness (PLMA).

* Periodic limb movements are clonic type movements (or uncontrollable "jerks" - usually of the lower extremities

* The pathophysiology of PLMS in RLS is unknown but it is hypothesised that the entire spinal cord is abnormally hyperexcitable.

* Various sleep and neurologcal disorders are associated with PLMS (many of which are associated with abnormalities in the central dopamine system) and they may increase with age - the exact association with RLS is not yet established.

3. Family history - a familial occurrence is found in approximately 50-92% of patients with RLS of unknown cause. Early onset of RLS is more commonly familial.