Benign neonatal sleep myoclonus: a review of the literature

Restless Legs Syndrome and Other Common Sleep-Related Movement Disorders

OBJECTIVE

This article reviews common sleep-related movement disorders, including their clinical description, epidemiology, pathophysiology (if known), and evaluation and management strategies. This article will provide the reader with a good foundation for approaching concerns that are suggestive of sleep-related movement disorders to properly evaluate and manage these conditions.

LATEST DEVELOPMENTS

α2δ Ligands, such as gabapentin enacarbil, can be used for the initial treatment of restless legs syndrome (RLS) or in those who cannot tolerate, or have developed augmentation to, dopamine agonists. Another option is the rotigotine patch, which has a 24-hour treatment window and may be beneficial for those who have developed augmentation with short-acting dopamine agonists. IV iron can improve RLS symptoms even in those whose serum ferritin level is between 75 ng/mL and 100 ng/mL. At serum ferritin levels greater than 75 ng/mL, oral iron will likely have minimal absorption or little effect on the improvement of RLS. Research has found an association between RLS and cardiovascular disease, particularly in people who have periodic limb movements of sleep.

ESSENTIAL POINTS

RLS is the most common sleep-related movement disorder. Its pathophysiology is likely a combination of central iron deficiency, dopamine overproduction, and possibly cortical excitation. Treatment includes oral or IV iron. Dopaminergic medications can be very effective but often lead to augmentation, which limits their long-term use. Other sleep-related movement disorders to be aware of are sleep-related rhythmic movement disorder, nocturnal muscle cramps, sleep-related propriospinal myoclonus, sleep bruxism, and benign myoclonus of infancy.

Early-onset spontaneously relieved spasms of infancy in sleep: Electroclinical characteristics and differential diagnoses

PURPOSE

Infantile spasm-like paroxysms are often difficult to classify as epileptic or non-epileptic. We aimed to study spontaneously relieved (non-epileptic) spasms of infancy in sleep. Elucidation of the electroclinical characteristics and differential diagnoses of such spasms could facilitate accurate diagnosis in the future.

METHODS

We retrospectively analyzed the clinical data, video-EEG recordings, and other laboratory test results of patients with spontaneously relieved spasms of infancy during sleep. All the enrolled patients were followed up for at least 5 months.

RESULTS

Seven infants were included in this study. The median age at spasm onset was 0.5 months (range: 0.1-2 months). The episodes were characterized by clusters of non-epileptic spasms of the head, trunk, or extremities lasting approximately 0.5-2 s, and were validated by ictal electromyography (EMG)/video EEG. Episodes occurred several times daily in clusters, particularly during sleep; two patients also experienced episodes while awake. Additionally, non-epileptic jerks were recorded in 3 patients. All non-epileptic spasms were completely resolved 2 weeks to 3 months after onset. Moreover, neuropsychomotor development in all patients was normal at the last follow-up (5 to 12 months).

CONCLUSIONS

Spontaneously relieved spasms of infancy in sleep is a self-limiting movement disorder characterized by onset between 0.1 and 2 months of age, and by clusters of spasms occurring in sleep. Correct differential diagnosis relies on familiar clinical and electrophysiological features.

Is it really a seizure? The challenge of paroxysmal nonepileptic events in young infants

Paroxysmal nonepileptic events (PNE) comprise of a variety of nonepileptic behaviors and are divided into various types. A more accurate diagnosis is possible by examining the video clip provided by the caregiver. In infants, physiologic PNE accounts for the majority of the PNE. It is important to exclude epilepsy, for which blood tests, electroencephalography, and imaging tests can facilitate differential diagnosis. Since most PNE have a benign progress, symptoms often improve with age and without special treatment. Therefore, it is important to reassure the caregivers after making an accurate diagnosis.

Neurodevelopmental outcomes of neonatal non-epileptic paroxysmal events: a prospective study

AIM

To report on psychomotor development and outcomes in term born neonates with non-epileptic paroxysmal events (NEPEs).

METHOD

From October 2017 to March 2019 we enrolled 38 consecutive term born neonates (22 males, 16 females; aged between 0-28d), born at the University Hospital San Marco in Catania, Italy, with NEPEs. We performed the Hammersmith Neonatal Neurological Examination scale (at enrolment), the Hammersmith Infant Neurological Examination (HINE) scale (at age 3, 6, 9, and 12mo), and the Griffiths scale (at age 12mo).

RESULTS

The age at onset of first paroxysmal manifestations ranged from birth to 4 days. We recorded a suboptimal global score in 18 out of 38 patients at enrolment and in 10 out of 38 patients at age 3 months (>70% of these infants were male); all events disappeared within 6 months of life. At age 6, 9, and 12 months, all infants scored within normal values on the HINE and Griffiths scale.

INTERPRETATION

Patients with NEPEs achieve neurodevelopment optimal scores within their first year of life.

WHAT THIS PAPER ADDS

Neonates experiencing non-epileptic paroxysmal events (NEPEs) can be examined with the Hammersmith Neonatal Neurological Examination, Hammersmith Infant Neurological Examination, and Griffiths scale at follow-up. Newborn infants with NEPEs achieve optimal scores within the first year of life.

Clinical and Genetic Overview of Paroxysmal Movement Disorders and Episodic Ataxias

Paroxysmal movement disorders (PMDs) are rare neurological diseases typically manifesting with intermittent attacks of abnormal involuntary movements. Two main categories of PMDs are recognized based on the phenomenology: Paroxysmal dyskinesias (PxDs) are characterized by transient episodes hyperkinetic movement disorders, while attacks of cerebellar dysfunction are the hallmark of episodic ataxias (EAs). From an etiological point of view, both primary (genetic) and secondary (acquired) causes of PMDs are known. Recognition and diagnosis of PMDs is based on personal and familial medical history, physical examination, detailed reconstruction of ictal phenomenology, neuroimaging, and genetic analysis. Neurophysiological or laboratory tests are reserved for selected cases. Genetic knowledge of PMDs has been largely incremented by the advent of next generation sequencing (NGS) methodologies. The wide number of genes involved in the pathogenesis of PMDs reflects a high complexity of molecular bases of neurotransmission in cerebellar and basal ganglia circuits. In consideration of the broad genetic and phenotypic heterogeneity, a NGS approach by targeted panel for movement disorders, clinical or whole exome sequencing should be preferred, whenever possible, to a single gene approach, in order to increase diagnostic rate. This review is focused on clinical and genetic features of PMDs with the aim to (1) help clinicians to recognize, diagnose and treat patients with PMDs as well as to (2) provide an overview of genes and molecular mechanisms underlying these intriguing neurogenetic disorders.

Benign Neonatal Sleep Myoclonus Evokes Somatosensory Responses

PURPOSE

Benign neonatal sleep myoclonus is a common nonepileptic condition occurring in neurologically normal full-term newborns. During jerks, EEG has always been described as normal. The aim of this study was to describe EEG changes associated with the myoclonic jerks.

METHODS

Polygraphic video-EEG recordings of four full-term neonates presenting benign neonatal sleep myoclonus were studied. Myoclonic jerks were analyzed regarding their topography, frequency, propagation pattern, and reflex component. EEG averaging time-locked to myoclonic jerks and to somatosensory stimuli (realized by tapping on palms and feet) was performed to study eventual EEG correlates of myoclonus and to asses somatosensory evoked responses-for the latter, two control newborns were added.

RESULTS

Visual analysis of the EEG disclosed theta band slow waves on central and vertex electrodes concomitant to myoclonic jerks and jerk-locked back-averaging disclosed a sequence of deflections, not preceding, but following the myoclonus. This response predominated on the vertex electrode (CZ) and consisted of five components (N1, P1, N2, P2, and N3), with only the three later components being constantly present (at 110, 200, and 350-500 ms, respectively). Back-averaging locked to the tactile stimuli in four subjects and two control newborns showed similar components and were comparable to those described in the literature as late somatosensory evoked responses in full-term newborns.

CONCLUSIONS

Myoclonic jerks in benign neonatal sleep myoclonus can evoke visually identifiable EEG potentials on vertex electrodes corresponding to somatosensory responses. This EEG aspect may be misleading and could give rise to an anti-seizure treatment that mostly worsens the condition.

Transient benign paroxysmal movement disorders in infancy

This review summarizes the current empirical and clinical literature on benign paroxysmal movement disorders in infancy most relevant to practitioners. Paroxysmal benign movement disorders are a heterogeneous group of movement disorders characterized by their favourable outcome. We pay special attention to the recognition and management of these abnormal motor conditions strongly suggestive of epileptic disorders. They include: neonatal jitteriness; benign neonatal sleep myoclonus; benign paroxysmal tonic upgaze; paroxysmal tonic downgaze, benign paroxysmal torticollis and benign polymorphous movement disorder of infancy.

Reflex Myoclonic Epilepsy of Infancy: Seizures Induced by Tactile Stimulation

Myoclonic epilepsy with reflex seizures in infancy is an extremely rare condition, in which seizures are provoked mainly by auditory or auditory-tactile stimuli. To increase the awareness of pediatricians regarding this underrecognized condition, we describe a child with seizures provoked only by the tactile stimulation of specific areas of the head and face.

Paroxysmal nonepileptic motor phenomena in newborn

INTRODUCTION

Understanding the pathophysiological meaning of paroxysmal nonepileptic motor phenomena in newborns represents a challenge for the clinicians of the Neonatal Intensive Care Unit.

METHODS

This paper provides an extensive review of the most frequent paroxysmal nonepileptic motor phenomena in newborns, in order to improve the knowledge about this sub-topic of the neonatal pathology and to guide the diagnostic-therapeutic approach.

RESULTS

The correct identification of an epileptic form, among different motor phenomena, which may clinically mimic seizures, is essential for a correct management, avoiding overtreatment. However, it is likewise important to know and to be able to identify other rare neurological conditions, such as hyperekplexia, spinal muscular atrophy, acute bilirubin encephalopathy, that could make a first appearance with paroxysmal motor manifestations, needing specific diagnostic work-up and treatment.

CONCLUSIONS

These clinical events should not be underestimated because, even if many times they are physiological and age-related, sometimes they could be the visible signs of an underlying epileptic or nonepileptic neurological disease.

Neonatal seizures-part 1: Not everything that jerks, stiffens and shakes is a fit

The neonatal period is the most frequent time of life to have epileptic seizures. However, neonates can also exhibit unusual movements that are not epileptic seizures. Differentiating between epileptic and non-epileptic movements can be difficult. Many neonatal seizures exhibit few or no clinical features at all. This article is for the benefit of paediatric trainees and reviews the published evidence on which neonatal movements are likely to be epileptic seizures and which are not. We also discuss epileptic seizure classification.

Acute movement disorders in children: experience from a developing country

We describe acute movement disorders in 92 children, aged 5 days to 15 years, from an Indian tertiary hospital. Eighty-nine children had hyperkinetic movement disorders, with myoclonus in 25, dystonia in 21, choreoathetosis in 19, tremors in 15, and tics in 2. Tetany and tetanus were seen in 5 and 2 children, respectively. Hypokinetic movement disorders included acute parkinsonism in 3 children. Noninflammatory and inflammatory etiology were present in 60 and 32 children, respectively. Benign neonatal sleep myoclonus in 16 and opsoclonus myoclonus syndrome in 7 accounted for the majority of myoclonus cases. Vitamin B12 deficiency in 13 infants was the most common cause of tremors. Rheumatic fever and encephalitis were the most common causes of acute choreoathetosis. Acute dystonia had metabolic etiology in 6 and encephalitis and drugs in 3 each. Psychogenic movement disorders were seen in 4 cases only, although these patients may be underreported.

Benign neonatal sleep myoclonus: our experience of 15 Japanese cases

PURPOSE

Benign neonatal sleep myoclonus is a non-epileptic movement disorder that may mimic neonatal seizures. The aim of this study was to clarify the clinical manifestations and outcomes in Japanese infants with benign neonatal sleep myoclonus.

METHODS

We reviewed the clinical manifestations and outcomes in 15 consecutive patients with benign neonatal sleep myoclonus (males: 10), including three paired familial cases, referred to our center between 1996 and 2011. The diagnosis of benign neonatal sleep myoclonus was based on a neonatal onset, characteristic myoclonic jerks that occurred during sleep, and normal electroencephalogram findings.

RESULTS

All were healthy full-term neonates at birth. The age at onset ranged from 1 to 18 days (median: 7 days). Prior to referral to our center (3-8 weeks), two infants had been placed on antiepileptic drugs, without effects. During the clinical course, the myoclonic jerks resolved by 6 months in 14 of the 15 patients. On follow-up (final evaluation, mean: 38 months), all but one patient (speech delay) showed normal development. None developed epilepsy. Of note, migraine occurred after 5 years of age in three children, including one who developed cyclic vomiting syndrome, evolving to migraine. Another boy developed cyclic vomiting syndrome, a precursor of migraine, before 1 year, and was being followed. A high incidence of migraine was observed in five (42%) of 12 parents whose detailed family history was available.

CONCLUSION

Our study suggests that benign neonatal sleep myoclonus is related to migraine. With the high rate of familial cases, further genetic study, including migraine-related gene analysis, is necessary to determine the underlying mechanism responsible for benign neonatal sleep myoclonus.

Benign neonatal sleep myoclonus: an autosomal dominant form not allelic to KCNQ2 or KCNQ3

Benign neonatal sleep myoclonus is an uncommon, nonepileptic disorder characterized by myoclonic jerks appearing in the neonatal period that occur predominantly during sleep. Although self-limiting, the disorder is frequently confused with epileptic neonatal seizures. A few familial cases have been reported; however the genetics has not been studied. We ascertained 3 families with 2 or more affected individuals and analyzed the pedigrees. We used microsatellite markers to determine if the disorder was possibly linked to KCNQ2 or KCNQ3, the 2 genes that cause most cases of benign familial neonatal seizures, a disorder that it could be easily confused with. The 3 pedigrees, including one with 4 affected individuals, were suggestive of autosomal dominant inheritance. The loci for KCNQ2 and KCNQ3 were excluded in the 2 larger families. We conclude that benign neonatal sleep myoclonus can show autosomal dominant inheritance and is not allelic with benign familial neonatal seizures.

Classification of sleep disorders

The classification of sleep disorders is necessary to discriminate between disorders and to facilitate an understanding of symptoms, etiology, and pathophysiology that allows for appropriate treatment. The earliest classification systems, largely organized according to major symptoms (insomnia, excessive sleepiness, and abnormal events that occur during sleep), were unable to be based on pathophysiology because the cause of most sleep disorders was unknown. These 3 symptom-based categories are easily understood by physicians and are therefore useful for developing a differential diagnosis. The International Classification of Sleep Disorders, version 2, published in 2005 and currently undergoing revision, combines a symptomatic presentation (e.g., insomnia) with 1 organized in part on pathophysiology (e.g., circadian rhythms) and in part on body systems (e.g., breathing disorders). This organization of sleep disorders is necessary because of the varied nature and because the pathophysiology for many of the disorders is still unknown. The International Classification of Sleep Disorders, version 2 provides relevant diagnostic and epidemiological information on sleep disorders to more easily differentiate between the disorders.

Approach to neonatal seizures

Neonatal seizures can be difficult to recognize given the variation in their presentation. Hence, diagnosis and appropriate treatment may be delayed. Morphology of seizures in this age group is discussed, followed by common etiological entities. Special emphasis is laid on treatable disease states such as vitamin responsive seizure disorders and benign conditions that may not warrant aggressive treatment. Conditions that may have devastating neurological consequences are discussed in some detail so that the treating pediatrician can provide realistic information to the parents of such newborns. Imaging and laboratory workup is outlined, followed by guidelines for ordering and interpreting an electroencephalogram in this age group. Finally, treatment options in the form of antiepileptics are discussed with mention of new avenues for diagnosis and treatment that may become commonly employed in the future.

Benign convulsions in newborns and infants: occurrence, clinical course and prognosis

BACKGROUND

During early development severe epilepsies may appear, some with well established occurrence. Benign non-epileptic and epileptic paroxysmal syndromes with excellent prognosis occur in the same period. There are no exact data on their occurrence.

AIM

We have reviewed medical histories of children with benign non-epileptic or benign epileptic events: benign myoclonus of early infancy, benign neonatal sleep myoclonus, benign sleep myoclonus in infancy, benign partial epilepsy in infancy (BPEI) and benign infantile familial convulsions (BIFC) were established. The occurrence, clinical characteristics and prognosis of these syndromes were evaluated.

METHODS

Inclusion criteria were met in 31 children. Research included retrospective analysis of clinical characteristics, laboratory values, neuroimaging and neurophysiological assessments, followed by evaluation of psychosocial development with the use of the Strengths and Difficulties Questionnaire (SDQ), fulfilled by parents.

RESULTS

In our group the incidence of benign non-epileptic convulsions was 6.69 per 10 000 live births and the incidence of benign epileptic convulsions was 1.35 per 10 000. Male/female ratio in the group of children with non-epileptic events was 2.1:1. Among non-epileptic group 5 out of 23 children and among epileptic group 3 out of 8 children had minimal, mild or moderate abnormalities at neurological assessment at the time of the first clinical examination. Nonspecific changes in laboratory values were seen in 6 out of 23 in the non-epileptic and in 1 out of 8 children in the epileptic group. Neurophysiological assessments showed subtle changes in 4/23 in the non-epileptic and 6/8 in the epileptic group. Neuroimaging was not optimal in 5/23 with non-epileptic and 3/8 with epileptic events. Analysis of SDQ did not show significant deviations in psyhosocial development. Statistically significant deviation was observed only in relations with peers (p = 0.009).

CONCLUSIONS

Benign neonatal and infantile convulsions are more frequent than severe epilepsies of the same age period. Results show higher proportion of males with benign non-epileptic conditions. No deviations in further development was found. Laboratory values, neuroimaging and neurophysiological assessments were normal or nonspecifically changed.