Spinal cord injuries (SCI) are common in veteran populations.1 Veterans with spinal cord injuries and disorders (SCI/D) also may have concurrent sleep disturbances. Spinal cord injury typically causes spasticity.2,3 Hypersensitivity of the flexor reflex pathways is believed to cause painful muscle spasms in patients with SCI.4 Neuropathic pain at or below the level of the lesion also is common.
Restless legs syndrome (RLS) is a common sleep disorder that affects sleep quality and can occur concomitantly with spinal cord lesions.5 In about 80% of RLS cases, involuntary movements of legs across hip, knee, and ankle joints during sleep, known as periodic limb movement during sleep (PLMS), occurs.6 Several studies showed increased prevalence of PLMS in patients with SCI, and some case reports suggest an increased prevalence of RLS in this population.7,8 One small study showed that 100% of patients with SCI had symptoms of RLS.6 Another study found that SCI could trigger PLMS.8
The pathophysiology of RLS and PLMS in patients with SCI is not fully understood, but case reports describing PLM in SCI patients points to a possible role of central pattern generators and the flexor reflex afferents in the pathophysiology of PLMS.9,10 Changes of the tissue microstructure in the midbrain and upper cervical spinal cord have been described in patients with RLS.11The objective of this study was to assess the prevalence of RLS in a veteran population with SCI/D and to determine possible neuroanatomical patterns involved in RLS and SCI/D.
Methods
The institutional review and ethical approval boards of the Minneapolis VA Health Care System approved the study. Within the VA system, 666 patients with SCI/D were identified using a national database. Of the 666 people, 316 were excluded, 199 were included, and 151 were deceased.
Patients aged between 18 and 65 years were included in the study. Charts of patients who had been discharged with the diagnosis of SCI from 2002 to 2008 were studied. All patients met the inclusion criteria of the International Restless Legs Syndrome Study Group diagnosis.
Exclusion criteria were as follows: Patients with evidence of brain pathology (eg, stroke), concurrent neurologic condition associated with RLS (Parkinson disease, spinocerebellar ataxia, peripheral neuropathy), concurrent psychiatric condition within the setting of treatment with dopamine antagonists, secondary causes of RLS (renal failure/uremia, iron deficiency, rheumatoid arthritis, and pregnancy) and a recent history of alcohol or drug misuse or current evidence of substance use of < 1 year.
A patient list was compiled that included the etiology of the SCI (vascular injury, multiple sclerosis [MS], trauma, unknown, and other), the level(s) and completeness of the SCI per radiology report, RLS pharmacotherapies, and pertinent medical history.
Axial T2-weighted images on magnetic resonance imaging (MRI) scans were retrospectively reviewed. Sagittal T1/T2-weighted and axial T2-weighted sequences were performed routinely on all patients with spinal cord lesions. The analysis included the extension of the lesion on both sagittal and axial distributions. The anatomic location of the cord lesion was categorized by the following: (1) pure gray matter (central cord); (2) white matter (dorsal [D], dorsolateral [DL], ventral [V], ventrolateral areas [VL]).
A questionnaire using standard diagnostic criteria for RLS was mailed to the 199 patients who met the inclusion criteria (Appendix A).
All analyses were carried out using StataCorp STATA 13 (College Station, TX). Descriptive statistics were used. The analyses were carried out using chi-square and Fisher exact tests. Differences between the groups were considered statistically significant at P < .05. The data were analyzed to obtain point prevalence among patients with SCI, and comparisons were made among the different subgroups.
Results
Of the 162 patients who chose to participate in the study, the sleep specialists confirmed 31 (19%) to have RLS, 112 (69%) were confirmed negative for RLS, and an additional 19 (12%) screened positive for RLS but were not confirmed to have RLS by the sleep specialists (Figure 1).
The etiology of SCI was subdivided into 4 groups: MS, trauma, vascular, and other/unknown. Within each group (– RLS vs + RLS), MS and trauma were the most common etiologies with 55% MS and 36% trauma in the + RLS group.
When comparing RLS among the spinal cord levels (cervical, thoracic, lumbar and cervical + thoracic), only the cervical + thoracic subgroup (18% + RLS vs 5% – RLS) showed a significant difference (Figure 2).
There was no significant difference found with the prevalence of RLS in the axial plane of the spinal cord lesions (ventral/ventro-lateral/central cord vs dorsal/dorsolateral) or by the completeness of spinal cord lesions, P = .76. There was a higher prevalence of incomplete cord injury, however, within each subgroup of RLS.
The Mann-Whitney test was used to analyze the burden of disease in both groups (+ RLS vs – RLS). Moderate level of burden was most frequently reported with a higher prevalence within the + RLS group. Of those receiving treatment for RLS, 71% were + RLS vs 46% – RLS with a P value of .01. Symptoms of RLS after cord injury were 89% + RLS vs 55% – RLS with a P value of .03.