Subclinical sensory neuropathy in late-onset restless legs syndrome

To determine the prevalence of different forms of peripheral neuropathy in patients with restless legs syndrome (RLS) and correlate the findings with other clinical characteristics.

RLS is characterized by a desire to move the extremities, often associated with paresthesias or dysesthesias, motor restlessness, worsening of symptoms with rest with relief by activity, and worsening of symptoms in the evening or night. The association between RLS and peripheral neuropathy remains controversial. The observation that many patients with small-fiber neuropathy also complain of RLS prompted this prospective case series.

Twenty-two consecutive patients with RLS were evaluated for evidence of large-fiber neuropathy (LFN) and small sensory fiber loss (SSFL).

In eight of the 22 (36%) patients, neuropathy was identified. Three patients had pure LFN; two had mixed LFN and SSFL; and three had isolated SSFL. The SSFL group had a later onset of RLS (p < 0.009), reported pain in their feet with RLS more frequently (p < 0.001), and tended to have no family history of RLS (p < 0.078). Patients with LFN did not have similar associations with age at onset, family history status, or presence of pain.

The results suggest that two forms of RLS exist: one is triggered by painful dysesthesias associated with SSFL, has later onset, and no family history; and one without involvement of SSF, with an earlier onset age, positive family history for RLS, and no pain. The authors hypothesize that patients with the SSFL subtype of RLS will preferentially respond to neuropathic pain medications.