Nocturnal Periodic Leg Movements in Spinal Cord Injury Olli Kurkela1, Aaro Salminen1,3, Eerika Koskinen2, Teemu Luoto2, Ville Rimpilä1,3, Juha Öhman2, Olli Polo1,2,3 1) Unesta Research Centre, Tampere, Finland 2) Tampere University Hospital, Finland 3) University of Tampere, Finland Introduction Table 1. Demographic data. ASIA = American spinal injury association impairment scale (A means complete lesion) Table 2. Sleep parameters of the patients. tcCO2 = transcutaneous carbon dioxide Nocturnal periodic leg movements (PLM) have been suggested to have their origin in the central nervous system because they can be suppressed by dopaminergic therapy (Montplaisir 1986). Also a spinal origin of PLMs has been suggested. (Clemens 2006) PLMs have been described to always be accompanied by responses on the cortex and heart rate in subjects with restless legs syndrome. (Ferri 2007) The autonomic nervous system has been suggested to be involved in the generation of PLM. (Guggisberg 2007) However, periodic leg movements (PLM) occur also in patients with complete spinal cord injury (SCI) (Yokota 1991, Lee 1996, Telles 2011), challenging the hypothesis of central origin. Demographics Age 60.2 (13.2) Gender Male 17 Female 8 ASIA A 4 B C 3 D Time since injury (years) 11.1 (10.5) Sleep parameters  Mean (St dev) Epworth Sleepiness Scale 6.3 (4.6) TST 335.3 (95.8) Sleep latency (min) 25.8 (24.4) REM Sleep (% of TST) 12.7 (7.8) SWS (% of TST) 37.4 (17.0) AHI (/h) 17.7 (20.5) SaO2 mean (%) 94.4 (1.5) SaO2 nadir (%) 82.8 (9.3) TcCO2, wake (kPa) 5.76 (0.88) TcCO2, SWS (kPa) 6.11 (1.05) TcCO2, REM (kPa) 6.29 (1.06) PLMI (/h) 39.7 (56.0) Rationale In previous studies, PLMs have been reported in patients with spinal cord injury as case reports or in small populations with only patients with a complete lesion. In the current study we aimed to confirm the existence of PLMs in a larger patient population and with various degrees of SCI. The goal was to investigate the morphology of the PLM, and to assess if the incidence of PLM is correlated with the class of injury or the time since injury. Methods Figure 1. The PLMs of one patient occurred at times bilaterally but with a different periodicity in different legs. The patient is a 63-year-old man with an ASIA class C spinal cord injury. The figure is a 10-minute extract of a full night sleep recording. Full polygraphic sleep recording, with transcutaneous carbon dioxide (tcCO2) monitoring, was performed in 25 patients (17 men, 8 women) with spinal cord injury. The current study was a part of a larger study focusing on neuroimaging and respiratory and urologic examinations in patients with spinal cord injury. Four subjects had American Spinal Injury Association (ASIA) class A injury, whereas 21 were of ASIA classes C-D. Demographic data can be seen in Table 1. Sleep staging was performed, and PLMs were analyzed from each recording according to the WASM scoring criteria. Movements related to breathing events were not included. PLM indexes were correlated with the ASIA classification of the injury. Results Figure 2. A patient with PLMs disconnected from cortical activity. The episodes of apnea produce EEG arousals, but leg movements occur independently. The patient is a 34-year-old male with ASIA class A spinal cord injury. The figure is a 10-minute extract of a full night sleep recording. Sleep parameters of the patients can be seen in Table 2. PLM was a common finding, present in 11 / 25 patients. When present, the average PLM-index was 86.6 /h. In all 11 patients the PLM index was higher than 25 /h. In 10 patients with PLM the SCI was of ASIA class C-D, one was ASIA A. The PLM occurred in all sleep stages, including REM sleep and wakefulness. In 4 patients the PLM index exceeded 120 / h. The PLM index did not correlate with ASIA class of injury or time since injury. In two cases with high PLMI (close to 150/h) (ASIA class A and C) no heart rate or cortical events were associated with PLM. The PLM in these two patients were never bilateral. Conclusions References In our patients with SCI the incidence of PLM was higher than previously reported. The results suggest that PLMs are a common finding in patients of all classes of SCI, including complete lesion (ASIA A). The appearance of PLMs in patients with complete spinal cord lesion does not support central origin of PLM. The absence of cortical and heart rate responses to PLM in some patients suggests that the central responses could be secondary to the leg movements. 1. Montplaisir J et al. Clin Neuropharmacol. 1986;9(5):456-63. 2. Clemens S et al. Neurology. 2006 Jul 11;67(1):125-30. 3. Ferri I et al. Clin Neurophysiol. 2007 Feb;118(2):438-48. 4. Guggisberg AG et al. Sleep. 2007 Jun;30(6):755-66. 5. Yokota T et al. J Neurol Sci. 1991 Jul;104(1):13-8. 6. Lee MS et al. Mov Disord. 1996 Nov;11(6):719-22. 7. Telles SC et al. J Neurol Sci. 2011 Apr 15;303(1-2):119-23. Contact information: olli.kurkela@unesta.fi