Objective: Neurophysiological studies on painful legs moving toes (PLMT) syndrome are limited. This study aims to characterize the neurophysiological features of PLMT and assess whether these movements are associated with features of functional movement disorders.

Background: PLMT syndrome is characterized by repetitive, spontaneous movements of the toes or feet in a limb affected by pain.¹ There is debate whether there are functional components to the movements. This debate arises from clinical observations that the movements diminished with voluntary activities of either the affected or contralateral limb.^{2, 3}

Method: Six patients clinically diagnosed with PLMT (Table 1), underwent multichannel electromyogram (EMG) and electroencephalogram (EEG) recordings. Surface EMG was performed on the extensor and flexor muscles of the toes and ankles at rest and while preforming different conditions (Table 2), and EEG was recorded from C3, C4, Cz, FC3, FC4 and FCz, with simultaneous video recording of the movements.

Results: In three patients, the movements involved both feet. EMG burst duration varied between 100 and 700 ms, with semi-rhythmic movements generally below 2 Hz, though they occasionally reached up to 4 Hz in two patients. At times, the movements exhibited dystonic posturing, with EMG bursts lasting more than 10 seconds. A movement-related cortical potential (MRCP) beginning more than one second before toe movements was identified in one patient. (Figure 1). This patient also showed suppression of movements through voluntary effort and ballistic movement of the contralateral leg, and temporary entrained activity in the affected foot. In patients without MRCP, varying degrees of distractibility were observed in all. One patient exhibited partial voluntary suppression, but none demonstrated entrainment or suggestibility.

Conclusion: PLMT syndrome is heterogeneous. Most toe and foot movements in PLMT are not associated with MRCPs but exhibit several features suggestive of attentional or volitional control.

Table 2. Summary of neurophysiological findings

Table 1. Demographic profiles

Figure 1. Movement-related cortical potentials

References: 1. Spillane JD, Nathan PW, Kelly RE, Marsden CD. Painful legs and moving toes. Brain 1971;94(3):541-556.
2. Stone J, Erro R. Functional (psychogenic) painful legs moving toes syndrome. Mov Disord 2014;29(13):1701-1702.
3. Vanegas-Arroyave N, Panyakaew P, Lamichhane D, Shulman L, Hallett M. Possible Functional Moving Toes Syndrome. Tremor Other Hyperkinet Mov (N Y) 2016;6:352.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/voluntariness-in-painful-legs-moving-toes-insights-form-neurophysiological-studies/