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Background
Restless legs syndrome (RLS), also known as Willis-Ekbom disease (WED), is a motor and circadian sleep disorder that commonly causes insomnia due to difficulty falling asleep. 1 The main features of RLS/WED are the urge to move legs at night time, which often occurs with a strange discomfort in lower limbs, and sudden relief after starting the activity. 2 In most cases, patients also experience involuntary and periodic jerks affecting muscles of the legs during relaxed wakefulness or while they are sleeping (periodic limb movements, PLMs). The symptoms are usually confined to the lower limbs, nevertheless, other body parts may also be affected; particularly, a phenotypic variant of RLS/WED has been recently described in which symptoms were limited to the abdomen muscles. 3
Propriospinal myoclonus (PSM) is a type of spinal myoclonus in which myoclonic activity arises in the spinal cord but does not remain restricted to segmentally innervated muscles, spreading up and down the length of the spinal cord along propriospinal (intersegmental) pathways. 4-6
'PSM at sleep onset' is a distinct subtype of propriospinal myoclonus, which occurs during relaxed wakefulness when the patient attempts to fall asleep, making it difficult to initiate sleep and consequently causing insomnia; 7-9 in some patients it was reported in association with typical RLS/WED. 10
We report a case of a patient with a long history of insomnia in which clinical features suggest an atypical RLS associated with myoclonic jerks involving the abdominal wall, in which video-polysomnography demonstrates the presence of a spinal myoclonus with characteristics of a PSM-like at sleep onset.
Case presentation
An 81-year-old man had a family history positive for RLS in the mother. Medical history was relevant for hypertension, hypercholesterolaemia, abdominal aortic aneurism, coronary artery disease, mild renal insufficiency and left renal artery stenosis. The patient's concomitant medications were amlodipine (5 mg/day), bisoprolol (3 mg/day), irbesartan (150 mg/day), acetylsalicylic acid (160 mg/day), ticlopidine (250 mg/day) and simvastatin (20 mg/day).
Since he was 47 years old he reported of abdominal 'cramps' associated with unpleasant restless sensation of discomfort with the urge to move occurring in the evening when lying in relaxed wakefulness and when trying to fall asleep. These symptoms disappeared completely if the patient stood up and walked around. Initially, the symptoms occurred rarely,...