Perhaps no other organ in the body is affected as often and in as many ways as the brain is in patients with chronic kidney disease (CKD). Several factors contribute to the neurological disorders in CKD including accumulation of uremic toxins, metabolic and hemodynamic disorders, oxidative stress, inflammation, and impaired blood brain barrier among others. The neurological disorders in CKD involve both peripheral and central nervous system. The peripheral neurological symptoms of CKD are due to somatic and cranial peripheral neuropathies as well as a myopathy. The central neurological symptoms of CKD are due to the cortical predominantly cortical, or subcortical lesions. Cognitive decline, encephalopathy, cortical myoclonus, asterixis and epileptic seizures are distinct features of the cortical disorders of CKD. Diffuse white matter disease due to ischemia and hypoxia may be an important cause of subcortical encephalopathy. A special and more benign form of subcortical disorder caused by brain edema in CKD is termed posterior reversible encephalopathy. Subcortical pathology especially when it affects the basal ganglia causes a number of movement disorders including Parkinsonism, chorea and dystonia. A stimulus-sensitive reflex myoclonus is believed to originate from the medullary structures. Sleep disorder and restless leg syndrome are common in CKD and have both central and peripheral origin. This article provides an overview of the available data on the nature, prevalence, pathophysiology, consequences and treatment of neurological complications of CKD.

Objectives

The objective of this review is to provide updated information on the epidemiology, correlating factors and treatment of chronic kidney disease associated restless legs syndrome (CKD-A-RLS) in both adult and pediatric population.

Materials and methods

We have reviewed the Medline search and Google Scholar search up to May 2022, using key words restless legs syndrome, chronic kidney disease and hemodialysis and kidney transplant. The reviewed articles were studied for epidemiology, correlating factors, as well as pharmacologic and non-pharmacologic treatment options.

Results

Our search revealed 175 articles, 111 were clinical trials or cross- sectional studies and 64 were review articles. All 111 articles were retrieved and studied in detail. Of these, 105 focused on adults and 6 on children. A majority of studies on dialysis patients reported a prevalence between 15-30%, which is notably higher than prevalence of RLS in general population (5-10%). The correlation between presence of CKD-A-RLS with age, gender, abnormalities of hemogram, iron, ferritin, serum lipids, electrolytes and parathyroid hormones were also reviewed. The results were inconsistent and controversial. Limited studies have reported on the treatment of CKD-A-RLS. Non-pharmacological treatment focused on the effect(s) of exercise, acupuncture, massage with different oils and infra-red light whereas, pharmacologic treatment options include the effects of dopaminergic drugs, Alpha2-Delta ligands (gabapentin and pregabalin), vitamins E and C, and intravenous iron infusion.

Conclusion

This updated review showed that RLS is two to three times more common in patients with CKD compared to the general population. More patients with CKD-A-RLS demonstrated increased mortality, increased incidence of cardiovascular accident, depression, insomnia and impaired quality of life than those with CKD without RLS. Dopaminergic drugs such as levodopa, ropinirole, pramipexole and rotigotine as well as calcium channel blockers (gabapentin and pregabalin) are helpful for treatment of RLS. High quality studies with these agents are currently underway and hopefully confirm the efficacy and practicality of using these drugs in CKD-A-RLS. Some studies have shown that aerobic exercise and massage with lavender oil can improve symptoms of CKD-A- RLS suggesting that these measures can be useful as adjunct therapy.

Chronic kidney disease (CKD) results in various central nervous systems (CNS) disorders including cognitive dysfunction, depression, anxiety, movement disorders, seizures and encephalopathy. Uremic retention products, oxidative stress, inflammation and impaired blood-brain barrier have been implicated as the major mediators of CKD-induced CNS disorders. However, mechanisms of CKD-induced cerebral tissue oxidative stress, inflammation and impaired blood brain barrier have not been fully elucidated and were explored. Male Sprague Dawley rats underwent sham operation or 5/6 nephrectomy and were observed for 10 weeks. Arterial pressure, body weight, and renal function were monitored. Under general anesthesia the animals' cerebral cortex was harvested. Nuclear translocations of NF-κB and Nrf2 and their key target gene products, neuronal, endothelial and inducible NO synthase (NOS) isoforms, markers of oxidative, nitrosative and myeloperoxidase reactions, fibrosis mediators and key protein constituents of capillary endothelial junctional complex were determined by Western blot analysis. The CKD rats exhibited reduced body weight, hypertension, elevated serum urea and creatinine concentrations. Compared to control group cerebral cortex of the CKD group showed activation (increased nuclear translocation) of NF-κB, elevation of pro-oxidant and pro-inflammatory molecules, diminished nuclear translocation of Nrf2 and expression of cytoprotective antioxidant molecules and depletion of the key protein constituents of endothelial junctional complex. In conclusion CKD results in the cerebral tissue activation of inflammatory and oxidative pathways, inhibition of antioxidant and cytoprotective system and erosion of cerebral capillary junctional complex, events that contribute to CNS dysfunction and impaired blood brain barrier.