Objective: To describe phenomenology and prevalence of leg stereotypy disorder (LSD)

Background: LSD is characterized chiefly by repetitive, rhythmical, stereotyped leg movement when sitting (Jankovic 2016). Often wrongly attributed to “nervousness” the condition has no diurnal variation, does not have a sensory component, and must be otherwise differentiated from “restless legs syndrome” (RLS) and other stereotypies.

Methods: We sought to characterize LSD in two groups of subjects: 1. General population (GP) group, defined as individuals accompanying patients during their visits to Baylor’s Parkinson’s Disease Center and Movement Disorders Clinic who are not genetically related to the patients and 2. Movement disorders (MD) group, composed of consecutive patients with diagnoses of RLS, Parkinson disease, Tourette syndrome, and tardive dyskinesia. All individuals were initially screened using a 10-point LSD screening questionnaire (LSQ) (Jankovic 2016). Those with a score of ≥5/10 were categorized as LSD and completed a rating scale and a form containing various demographic and clinical characteristics.

Results: Out of 92 screened individuals (57 GP, 35 MD), 49 (59% female) were identified with LSD. Their mean age was 46.9 years and mean age at onset of LSD was 17.9 years. In 65% the symptoms were predominantly manifested in one leg and 72% had a positive family history. The prevalence was higher in the MD group (65.7%) than the GP group (45.5%) (p<0.05); there was no statistically significant difference in the prevalence of LSD in the various movement disorders. Receiving operating characteristic (ROC) analysis (AUC = 0.96; 95% CI = 0.89-1.00), identified 5/10 screening items with best statistical fit, and endorsing 2/5 of these items provided sensitivity and specificity values of .86  and .96, respectively.    

Conclusions: Despite some limitations, the high estimated overall LSD prevalence of 53% suggests that this may be the most common movement disorder. Further studies are needed to determine its prevalence and pathophysiology, but genetic factors clearly play an important role.

References: Jankovic J. Leg stereotypy disorder. J Neurol Neurosurg Psychiatry. 2016 Feb;87(2):220-1

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MDS Abstracts - https://www.mdsabstracts.org/abstract/leg-stereotypy-disorder-clinical-characteristics-and-prevalence/