Periodic limb movement during sleep (PLMS) is defined as repetitive and regular involuntary movement. It occurs primarily in the legs during sleep and usually consists of foot dorsiflexion and less often flexion at the knee or the hip.¹ PLMS occurs 10-20% of general population and most prevalently in restless legs syndrome (RLS), which accounts for 80-90% of cases, but these movements can co-occur with a variety of sleep, medical, and neurological disorders and even with stroke.2-7 Previously reported cases of PLMS following ischemic stroke exhibited different clinical manifestations depending on the lesion site. These were associated with motor weakness with or without RLS. Here we report a case of contralateral PLMS without RLS following ischemic stroke in the right globus pallidus.

A 53-year-old right-handed man was admitted to our hospital complaining of dysarthria, which had started approximately 2 days prior to admission. There was no previous history of medical conditions or drug use. The patient had no other symptoms besides dysarthria. On neurological examination, the patient was found to be alert, and there were no changes in motor strength, sensory abilities, pathologic reflexes, or cortical function. The brain 3.0-tesla magnetic resonance imaging (Achieva 3.0T; Philips, Eindhoven, Netherlands), including diffusion-weighted imaging, revealed an acute ischemic stroke in the right globus pallidus along with a tiny portion of adjacent area (Fig. 1). Besides snoring, the patient had no history of abnormal movement or sensation in the legs, insomnia, daytime sleepiness, or other abnormal sleeprelated behavior or movement before the ischemic stroke. During his hospital stay, repetitive movement in the left leg during sleep was observed by chance. Video-polysomnography (COMET PSG; Grass Technologies, Twin 4.5.2 Software, Warwick, RI, USA) was performed, and it revealed regular and repetitive movement in the left great toe, intermixed with ankle dorsiflexion, and electroencephalographic microarousal following periodic movements (Fig. 2). The polysomnography began at 09:12:53 PM and ended at 04:08:48 AM the next day. Total sleep time was 303 min with sleep efficiency of 73.0%. Total periodic limb movements during sleep were 83 (left, 72; right, 11) with a PLMS-index of 16.4 (left, 14.3; right, 2.1). The apnea-hypopnea index was 17.6 with a minimum oxygen saturation of 92%. The patient had new onset of leg movements. He was treated with an antiplatelet agent and the risk factor for ischemic stroke was assessed. Since the patient had no accompanying subjective sleep disturbance due to PLMS, he was discharged without medication for PLMS.

Our patient predominantly experienced asymptomatic PLMS in the left leg, as indicated by video-polysomnography. On admission to hospital, the periodic movement was observed incidentally by his wife who was the caregiver. Based on the previous history, imaging studies, and polysomnographic findings, the patient was diagnosed with PLMS following stroke. The reported prevalence of PLMS in the population is 7.6%, and it is common even in the absence of other sleep complaints, particularly in elderly people. Therefore, PLMS is often discovered coincidentally on polysomnography.^8,9 However, both the patient and his wife denied that there was any abnormal limb movement during sleep or that he experienced any sleep disturbance before the ischemic stroke. Hence, we concluded that the ischemic stroke in the right globus pallidus was possibly responsible for the contralateral PLMS without RLS.

There have been several previous reports of PLMS following ischemic stroke corresponding to the lesion site,^2-6 which demonstrated different clinical manifestations (Table 1). In a prospective study, 54.3% of patients with supratentorial infarction had PLMS. The anatomical sites of PLMS were middle cerebral artery territory, anterior cerebral artery territory, corona radiata, basal ganglia, thalamus, and centrum semiovale. 7 However, this study questioned the possibility of premorbid PLMS before stroke. Although there was no detailed clinico-anatomical correlation in each case, most patients demonstrated PLMS contralateral to the lesion. The majority of PLMS cases following ischemic stroke was observed along with motor weakness, or during recovery periods. In the case of accompanying pyramidal tract damage, there was no clear RLS.^2-4,6 However, when damage to the extrapyramidal tract occurred, RLS was also observed.5 Unlike the case of PLMS following a lesion to the lenticulostriate region, no accompanying symptoms related to RLS were found in our patient.

Periodic limb movement during sleep is similar to the Babinski sign and occurs without plantar stimulation, which suggests a central origin. It is known that damage to the pyramidal tract in the cortex or subcortex leads to a loss of suppression of the reticular structures and, consequently, may lead to the symptoms commonly seen as a result of supratentorial lesion.¹⁰

In conclusion, our case presented PLMS without RLS, which developed following a globus pallidus infarction with no accompanying motor weakness. We suggest that the globus pallidus may be a neuroanatomical site within the basal ganglia involved in the pathophysiology of PLMS without RLS.