Objective: To evaluate and describe the visual kinematic characteristics of repetitive leg movements in individuals with leg stereotypy syndrome (LSS).

Background: Leg stereotypy syndrome (LSS) is a highly prevalent condition, marked by repetitive, rhythmic, and stereotypic leg movements, often occurring while seated but also manifested as a swaying movement of the body during standing[1]. One study showed that LSS manifests in up to 7% of the general population and 17% of patients diagnosed with movement disorders[2]. Possible reasons for the marked under-recognition of LSS include its symptomatic overlap with conditions such as anxiety, leg tremors leg-swinging, restless leg syndrome with periodic limb movements while awake, attention deficit hyperactivity disorder with impulsivity, and a form of self-gratification behavior or habit. Although usually familial, the pathophysiology of the condition is not yet well understood.

Method: In this retrospective study, we identified individuals diagnosed with LSS and videotaped at the Parkinson’s Disease Center and Movement Disorders Clinic, Baylor College of Medicine, Houston, Texas between 2000 and 2023. Only patients with LSS and without any co-morbidity were included in the study. Their medical records were carefully reviewed, and the demographic and clinical data were entered into a database. Video recorded leg movements were then analyzed using TremAn3 software. TremAn3 follows a former application with a similar aim [3], but it is based on a different design suited for more advanced analyses of rhythmic movements [4].

Results: We identified 9 individuals with LSS who were videotaped at our center. Of those, regular rhythmic oscillations of the legs were present in 7 cases, always with the toes resting on the floor with the heels raised. Frequency analysis showed values between 4.5 and 6.5 Hz, fairly consistent with a variance below 0.5 Hz in individual cases. The only exception was the one patient, where the oscillation frequency varied from 3.3 to 4.3 Hz. The frequency range between 1.8-2.6 Hz was consistent in the leg-crossed position for three patients [table 1].

Conclusion: In this study, 6 of 9 individuals with LSS showed 4.5-6.5 Hz regular rhythmic leg movements. Studies involving a larger LSS population with additional electrophysiological evaluations are needed to obtain further insights into this common movement disorder.

Table 1: Results of the kinematic analysis

References: 1. Jankovic J. Leg stereotypy disorder. J Neurol Neurosurg Psychiatry. 2016 Feb;87(2):220-1.
2. Lotia M, York MK, Strutt AM, Jankovic J. Leg stereotypy syndrome: phenomenology and prevalence. J Neurol Neurosurg Psychiatry. 2018 Jul;89(7):692-695.
3. Uhríková Z, Sprdlík O, Hoskovcová M, Komárek A, Ulmanová O, Hlaváč V, Nugent CD, Růžička E. Validation of a new tool for automatic assessment of tremor frequency from video recordings. J Neurosci Methods. 2011 May 15;198(1):110-3.
4. https://apps.microsoft.com/detail/9NL11TZLSFDP?hl=cs-cz&gl=CZ

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MDS Abstracts - https://www.mdsabstracts.org/abstract/leg-stereotypy-syndrome-phenomenological-and-quantitative-analysis/