Circadian fatigue or unrecognized restless legs syndrome? The post-polio syndrome model.

A comment on Circadian variation of fatigue in both patients with paralytic poliomyelitis and post-polio syndrome. by Viana CF, Pradella-Hallinan M, Quadros AA, Marin LF, Oliveira AS (2013). Arq Neuropsiquiatr; 71: 442-445. “It ought to be generally known that the source of our pleasure, merriment, laughter, amusement, as of our grief, pain, anxiety and tears, is none other than the brain” Hippocrates The discussion of this research paper may represent the starting point of the debate about the influence of sleep disorders on fatigue perception. These authors observed in a small cohort of patients with paralytic poliomyelitis (PP) and post-polio syndrome (PPS) a significant circadian variation of subjective fatigue evaluated by means of a validated scale. These authors showed a progressive worsening of fatigue during afternoon in both PP and PPS [1]. Polysomnographic variables did not correlate with fatigue, albeit restless legs syndrome (RLS) symptoms were not evaluated. PP is an acute poliovirus infection resulting in flaccid paralysis, due to poliovirus-induced apoptosis and consequent central nervous system injury, which leads to paralysis. Therefore, during its clinical course an increasing and progressive fatigue may represent an integral part of PP motor symptoms. In addition, more than 90% of patients with PP develop a delayed syndrome characterized by excessive fatigue [2]. PPS circadian impairment of fatigue may be more puzzling. it may be related to the presence of sleep disorders (i.e. sleep apnea, RLS and periodic limb movements of sleep (PLMS) previously described in PPS [3-5]. RLS and other sleep disorders have been reported in small PPS uncontrolled cohorts or single case reports, and in selected samples complaining of fatigue and sleepiness. In addition, fatigue represents a cardinal symptom of PPS, marked by a progressive course, and able to affect significantly patient quality of life [6]. Moreover, fatigue in PPS may be characterized by circadian changes, as recently showed by Viana and colleagues in a small cohort of PPS patients [1]. Although these authors did not explore clinical RLS in these PPS sample, it is intriguing to note that fatigue could resemble the circadian pattern of RLS symptoms. Therefore, RLS may represent an interesting model and a possible unifying hypothesis for fatigue in PPS similarly to other diseases both neurological (i.e. multiple sclerosis, myotonic dystrophies) and non-neurological (COPD, liver disorders) [2, 7-9]. Prevalence of RLS in these disorders has been reported as higher than in the general