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|Year : 2001 | Volume
| Issue : 4 | Page : 366-70
Periodic limb movement disorder : a clinical and polysomnographic study.
Dhanuka AK, Singh G
Division of Neurology, Dayanand Medical College and Hospital, Civil Lines, Ludhiana - 141001, Punjab, India.
Division of Neurology, Dayanand Medical College and Hospital, Civil Lines, Ludhiana - 141001, Punjab, India.
Periodic limb movement disorder (PLMD) is one of the commonest neurological disorders and causes significant disability, if left untreated. However, it is rarely diagnosed in clinical practice, probably due to lack of awareness and/or lack of necessary diagnostic facilities. Restless leg syndrome (RLS), aging, pregnancy, uraemia, iron deficiency, polyneuropathy are some of the common causes of secondary PLMD. Clinical presentation, polysomnographic findings and management of six patients of PLMD have been discussed in this report.
|How to cite this article:|
Dhanuka A K, Singh G. Periodic limb movement disorder : a clinical and polysomnographic study. Neurol India 2001;49:366
The syndrome of 'restless legs' or 'nocturnal myoclonus' has been known for several decades.,,, Coleman first noted that nocturnal myoclonus tends to occur at 20-40 seconds interval and suggested alternate name 'periodic movements in sleep'. In the recent literature, this term has been replaced by 'periodic limb movement in sleep' (PLMS) because these movements can occur in legs as well as in the arms. American sleep disorder association terms the overall condition as 'periodic limb movement disorder' (PLMD). Typical PLMS are characterised by repetitive flexion of the hips, knees and ankles 0.5 to 5 seconds in duration that recurs primarily in stages 1 and 2 of sleep. Besides restless legs syndrome (RLS), it can also be seen in older age, narcolepsy, uraemia, polyneuropathy, anaemia and pregnancy.,,,
Though the syndrome has been described in detail several decades ago it still remains unrecognised, missed or misdiagnosed in our day to day practice. The authors report six cases of periodic limb movement disorder. This article is intended to share the experience and enhance awareness.
In the sleep laboratory of Dayanand Medical College and Hospital, Ludhiana, six patients were diagnosed as having PLMD, between June 1997 to January 1999. These represent only those six cases, where diagnosis was confirmed by sleep studies. Cases of 'restless legs', diagnosed clinically and not subjected to sleep study, were not included in this study. An attempt was made to find out the cause of PLMD by proper history including family history and detailed neurological examination by one of the authors (AKD or GDS), complete blood counts, renal function test, serum electrolytes, fasting blood sugar and other relevant investigations like nerve conduction studies, X-ray of lumbosacral spine and serum tranferrin iron binding capacity. A therapeutic trial with Levodopa + Carbidopa combination was given. Clonazepam was added in case of failure. Minimum follow up period was three months.
Polysomnography (sleep study) was done with Medelac DG Examiner Plus (UK) in soundproof room. Patients were asked to shampoo their hair in daytime and not to apply any oil or cream on the scalp. They were advised not to alter their routine i. e. take their regular meals at usual time, dress in usual night suit and report to the lab atleast one hour prior to their usual time of sleep. Six to [eight] hours of recording was done depending on the patient's usual sleep pattern. They were explained about the nature of procedure beforehand and alcohol or hypnotics were not permitted for two to three days prior to and on the day of study. A four channel EEG was recorded alongwith two channels for electro-oculogram (EOG) and one channel each for ECG (electrocardiograph), respiratory movement at chest, oro-nasal airflow and continuous pulse oximetry (SpO2). Bilateral tibialis anterior (TA) surface EMG was recorded to detect PLMS.
Scoring PLMS : Typical periodic movements in sleep are characterised by repetitive flexion of the hips, knees and ankles, 0.5 to 5 seconds in duration that recurs primarily in stages 1 and 2 of sleep. When assessing the sleep recordings, atleast four movements separated by intervals of 5 to 90 seconds must be present before periodic movements in sleep can be scored. No absolute amplitude criteria is required for scoring PLMS. Scored PLMS are counted and divided by number of hours of sleep to yield a 'movement index'.
Six cases of PLMS were identified during the study period from June 1997 to January 1999. During this period, a total of 71 polysomnography studies (sleep studies) were carried out at our sleep lab, for different indications. All our patients with PLMS were male with age range of 35 years to 73 years. Duration of symptoms varied from 3 months to 30 years [Table I]. We got only severely affected patients because our institute is a tertiary care center in this region. Following is the illustration of a representative case. All cases are presented in Table no. I.
Case no. 1 (NKA) : A 36 year old male was referred for possible focal seizures disturbing his sleep. He had jerks of both lower limbs for the last 3 years especially during late hours of evening and it disturbed his sleep at night. His physician investigated him with EEG, CT scan of head and routine blood counts, all of which were found to be normal. Hence, he was diagnosed as focal seizures of unknown aetiology and started on antiepileptic medications. Over three years phenytoin, phenobarbitone and carbamazepine were tried in different doses, alone and in different combinations. At the time of referral, he was taking 1200 mg of carbamazepine daily in three divided doses without any relief. Neurological examination was unremarkable. A polysomnographic study was done. He had very frequent periodic limb movements during stage 1 and 2 of sleep, which badly affected his sleep. His sleep was poorly maintained. He had a total of 548 PLMS [Figure.1] during seven hours of sleep recording, and the movement index was 78.2. He was given Sinemet CR ¼ tablet, 1 hour before sleep. There was no response. Gradually (every 5th day), it was increased by ¼ tablet. At dose of 1 tablet per day, he had significant improvement. One month later, he was not satisfied with the result due to poor control of movements as well as appearance of movements early in the morning. Sinemet was stopped and clonazepam was started at 0.5 mg before sleep. It was gradually increased and at 2 mg dose, he had nearly complete remission of the symptoms. Carbamazepine was gradually stopped. After one year of follow up, he was fully asymptomatic and off carbamazepine and maintained on 2 mg clonazepam.
Restless leg syndrome (RLS) is characterised by - (i) the desire to move the limbs, usually associated with paraesthesias, (ii) motor restlessness, (iii) symptoms worse or present exclusively at rest with atleast temporary or partial relief by activity, (iv) symptoms worse in the evening or night. Further clinical signs include sleep disturbances, involuntary movements (periodic limb movement in sleep or wakefulness), a normal neurological examination (except in secondary RLS), a chronic clinical course and in some cases a positive family history. 80% cases of restless legs are associated with PLMS. However, both these disorders can occur independently. They may be primary or may be associated with a variety of medical conditions like old age, narcolepsy, uraemia, polyneuropathy, anaemia and pregnancy., Ekbom estimated a 5% prevalence of RLS in general population. Another study detected a prevalence of 2.5%. Most of the cases of the RLS are associated with PLMS but this is not necessary. Typical periodic movements in sleep are characterised by repetitive flexion of the hips, knees and ankles 0.5 to 5 seconds in duration, that recurs primarily in stages 1 and 2 of sleep. These involuntary movements may present no change in EEG or no evidence of arousal or they may be associated with K-complexes, K-alpha complexes, brief burst of alpha activity or other evidence of arousal. Patient may complain of disturbed sleep with frequent awakenings, daytime sleepiness or both; however many patients are asymptomatic, particularly if most of the PLMS are not associated with arousal. We have studied only severely symptomatic patients because of the referral pattern. Sleep pattern was disturbed in all our cases with frequent arousal. Maximum of 675 PLMS were noted in a single night of recording in case no 4.
According to western data, PLMS are common in the normal population particularly with advancing age. PLMS are present in 5% or more of the population aged 30 years to 49 years and present in 30% or more of the population aged 50 years or above., Similar data is not available for Indian population. Besides restless legs and advancing age, several other disorders/risk factors lead to PLMS as discussed earlier. Thus, it is one of the commonest disorder of elderly population, yet we rarely diagnose it. Hence, it may be called as 'the commonest disorder- you never heard of'. Early diagnosis will prevent unnecessary suffering (physical and mental) and inappropriate use of hypnotic with its accompanying problems. Response to treatment is dramatic. All patients in present study had good response to treatment and it was sustained during follow up (3 months to 12 months of follow up). Cure is possible if the cause can be removed such as iron deficiency (e.g. case no 4).
Dopaminergic drugs are considered the treatment of choice at present and include L-dopa, bromocriptine, pergolide and facilitating agents (selegeline). Usually, a single small dose of L-dopa + carbidopa is started 1 hour prior to sleep and the dose may be titrated upwards or if required a second dose may be given at midnight. A combination of short acting and long acting preparation of L-dopa may alleviate the need to give a second dose at midnight. In present study, a combination of short and long acting L-dopa was used in one case (case no 6) because the response to single evening dose of sustained release preparation (Sinemet CR) was not good. Many experts consider clonazepam as the drug of first choice. A reasonable initial regimen is to start 0.5 mg clonazepam in evening and gradual increase upwards as needed. Long-term nightly use of the benzodiazepines in the treatment of PLMS seems to be associated with only small risk of tolerance or addiction. Among alternative drugs, carbamazepine (200-400 mg) has been found to be effective treatment in two double blind studies., However, two of our cases were taking carbamazepine with a misdiagnosis of convulsions and did not respond. They responded to L-dopa (case no. 5) or clonazepam (case no. 1). It is possible that several patients are diagnosed as convulsions and receive carbamazepine and become symptom free, thus would not report to neurologists.
The cause of PLMD remains unknown. Evidence now suggests that there is a sleep-related failure of motor inhibition. A reticular or other subcortical origin has been proposed, because it never involves the face, suggesting generator below the level of facial nucleus in the brain stem. In addition, no electrically generated cortical potential has been found to precede the PLMS when EEG signals prior to PLMS are back-averaged., Functional MRI suggest that the red nucleus and brainstem area close to the reticular formation are involved in generation of PLMS in patients with RLS. Because of the good response to dopaminergic drugs, investigators have suggested underactivity of the endogenous dopaminergic system.
To conclude, RLS and PLMD are not unknown diseases in our community. One should have a high index of suspicion and a timely sleep study is required to confirm the presence of PLMS. Once diagnosed, the response to therapy is excellent.
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