Intracerebral recordings of minor motor events, paroxysmal arousals and major seizures in nocturnal frontal lobe epilepsy

Sleep and epilepsy: A clinical and pathophysiological overview

The interaction between sleep and epilepsy is complex. A better understanding of the mechanisms linking sleep and epilepsy appears increasingly important as it may improve diagnosis and therapeutic strategies in patients with epilepsy. In this narrative review, we aim to (i) provide an overview of the physiological and pathophysiological processes linking sleep and epilepsy; (ii) present common sleep disorders in patients with epilepsy; (iii) discuss how sleep and sleep disorders should be considered in new therapeutic approaches to epilepsy such as neurostimulation; and (iv) present the overall nocturnal manifestations and differential diagnosis between epileptic seizures and parasomnia.

Sleep and epilepsy: A snapshot of knowledge and future research lines

Sleep and epilepsy have a reciprocal relationship, and have been recognized as bedfellows since antiquity. However, research on this topic has made a big step forward only in recent years. In this narrative review we summarize the most stimulating discoveries and insights reached by the "European school." In particular, different aspects concerning the sleep-epilepsy interactions are analysed: (a) the effects of sleep on epilepsy; (b) the effects of epilepsy on sleep structure; (c) the relationship between epilepsy, sleep and epileptogenesis; (d) the impact of epileptic activity during sleep on cognition; (e) the relationship between epilepsy and the circadian rhythm; (f) the history and features of sleep hypermotor epilepsy and its differential diagnosis; (g) the relationship between epilepsy and sleep disorders.

Periodic limb movements during sleep: a narrative review

Objective

Using narrative review techniques, this paper evaluates the evidence for separable underlying patho-mechanisms of periodic limb movements (PLMs) to separable PLM motor patterns and phenotypes, in order to elucidate potential new treatment modalities.

Background

Periodic limb movement disorder (PLMD) is estimated to occur in 5–8% of the paediatric population and 4–11% of the general adult population. Due to significant sleep fragmentation, PLMD can lead to functional impairment, including hyperactivity and delayed language development in children, and poor concentration and work performance in adults. Longitudinal data demonstrate that those with PLMD are at greater risk of depression and anxiety, and a 4-fold greater risk of developing dementia. PLMD has been extensively studied over the past two decades, and several key insights into the genetic, pathophysiological, and neural correlates have been proposed. Amongst these proposals is the concept of separable PLM phenotypes, proposed on the basis of nocturnal features such as the ratio of limb movements and distribution throughout the night. PLM phenotype and presentation, however, varies significantly depending on the scoring utilized and the nocturnal features examined, across age, and co-morbid clinical conditions. Furthermore, associations between these phenotypes with major neurologic and psychiatric disorders remain controversial.

Methods

In order to elucidate potential divergent biological pathways that may help clarify important new treatment modalities, this paper utilizes narrative review and evaluates the evidence linking PLM motor patterns and phenotypes with hypothesised underlying patho-mechanisms. Distinctive, underlying patho-mechanisms include: a pure motor mechanism originating in the spinal cord, iron deficiency, dopamine system dysfunction, thalamic glutamatergic hyperactivity, and a more cortical-subcortical interplay. In support of the latter hypothesis, PLM rhythmicity appears tightly linked to the microarchitecture of sleep, not dissimilarly to the apnoeic/hypopneic events seen in obstructive sleep apnea (OSA).

Conclusions

This review closes with a proposal for greater investigation into the identification of potential, divergent biological pathways. To do so would require prospective, multimodal imaging clinical studies which may delineate differential responses to treatment in restless legs syndrome (RLS) without PLMS and PLMS without RLS. This could pave the way toward important new treatment modalities.

Sleep-Related Hypermotor Epilepsy: Etiology, Electro-Clinical Features, and Therapeutic Strategies

Sleep-related hypermotor epilepsy (SHE) is a group of clinical syndromes with heterogeneous etiologies. SHE is difficult to diagnose and treat in the early stages due to its diverse clinical manifestations and difficulties in differentiating from non-epileptic events, which seriously affect patients' quality of life and social behavior. The overall prognosis for SHE is unsatisfactory, but different etiologies affect patients' prognoses. Surgical treatment is an effective method for carefully selected patients with refractory SHE; nevertheless, preoperative assessment remains challenging because of the low sensitivity of noninvasive scalp electroencephalogram and imaging to detect abnormalities. However, through a careful analysis of semiology, the clinician can deduce the potential epileptogenic zone. This paper summarizes the research status of the background, etiology, electro-clinical features, diagnostic criteria, prognosis, and treatment of SHE to provide a more in-depth understanding of its pathophysiological mechanism, improve the accuracy in the diagnosis of this group of syndromes, and further explore more targeted therapy plans.

Polysomnographic features differentiating disorder of arousals from sleep-related hypermotor epilepsy

Objective

The differential diagnosis between sleep-related hypermotor epilepsy (SHE) and disorders of arousal (DOA) may be challenging. We analyzed the stage and the relative time of occurrence of parasomnic and epileptic events to test their potential diagnostic accuracy as criteria to discriminate SHE from DOA.

Methods

Video-polysomnography recordings of 89 patients with a definite diagnosis of DOA (59) or SHE (30) were reviewed to define major or minor events and to analyze their stage and relative time of occurrence. The “event distribution index” was defined on the basis of the occurrence of events during the first versus the second part of sleep period time. A group analysis was performed between DOA and SHE patients to identify candidate predictors and to quantify their discriminative performance.

Results

The total number of motor events (i.e. major and minor) was significantly lower in DOA (3.2 ± 2.4) than in SHE patients (6.9 ± 8.3; p = 0.03). Episodes occurred mostly during N3 and N2 in DOA and SHE patients, respectively. The occurrence of at least one major event outside N3 was highly suggestive for SHE (p = 2*e-13; accuracy = 0.898, sensitivity = 0.793, specificity = 0.949). The occurrence of at least one minor event during N3 was highly suggestive for DOA (p = 4*e-5; accuracy = 0.73, sensitivity = 0.733, specificity = 0.723). The “event distribution index” was statistically higher in DOA for total (p = 0.012) and major events (p = 0.0026).

Conclusion

The stage and the relative time of occurrence of minor and major motor manifestations represent useful criteria to discriminate DOA from SHE episodes.

Sporadic nocturnal frontal lobe epilepsy: A consecutive series of 8 cases

OBJECTIVE

To present findings on a series of cases of sporadic nocturnal frontal lobe epilepsy (NFLE), a form of NFLE that is infrequently reported, in contrast to familial (autosomal dominant) NFLE. Both forms of NFLE need to be distinguished from parasomnias, nocturnal temporal lobe epilepsy, and other nocturnal disorders.

METHODS

Eight consecutive cases of sporadic NFLE were evaluated at a sleep clinic in Taiwan. All patients had clinical evaluations, daytime waking and sleeping EEGs, brain MRIs, and overnight video-polysomnography (vPSG) with seizure montage.

RESULTS

Gender was equal (four males, four females); mean age was 18.4 yrs (range, 7-41 yrs). Age of NFLE onset was by puberty. Premorbid history was negative for any neurologic, medical or psychiatric disorder. NFLE subtypes: nocturnal paroxysmal dystonia, n=6; paroxysmal arousals, n=2. MRI brain scan abnormalities with clinical correlates were found in one patient. Daytime awake EEGs were negative for ictal/interictal activity in all patients, but two patients had daytime sleep EEGs with interictal epileptiform EEG activity. During vPSG studies, three of eight patients with NFLE seizure events had concurrent epileptiform EEG activity, and two patients had interictal epileptiform EEG activity during their vPSG studies. No case had a spontaneous remission. Anticonvulsant therapy was highly effective in all eight cases (>75% reduction in seizure frequency).

DISCUSSION

These cases confirm that sporadic NFLE closely resembles familial NFLE, and comprises a set of distinct clinical manifestations, with variable intensity, and variable scalp EEG epileptiform abnormalities across sleep and wakefulness, which have previously been identified in Caucasian patients from Europe and North America.

Sleep and epilepsy

The intimate relationship between sleep and epilepsy has long been recognized, yet our understanding of the relationship is incomplete. In this article we address four key issues in this area. First, we consider the reciprocal interaction between sleep and epilepsy. Sleep state clearly influences seizure onset, particularly in certain epilepsy syndromes. The converse is also true; epilepsy may disrupt sleep, either directly through seizures and epileptiform activity, or indirectly through medication-related effects. Unraveling the influences of sleep stage, epilepsy syndrome, and drug effects is challenging, and the current state of knowledge is reviewed. Secondly, accurate diagnosis of sleep-related epilepsy can be difficult, particularly the distinction of nocturnal frontal lobe epilepsy (NFLE) from arousal parasomnias. The challenges in this area, along with work from the authors, are discussed. Thirdly, we will explore the putative relationship between obstructive sleep apnea (OSA) and epilepsy, including the effect of OSA on quality of life; this will lead us to a brief exploration of the effects of OSA on neuroendocrine function. Finally, we will review the evidence surrounding the role of sleep in sudden unexpected death in epilepsy (SUDEP).

Diagnostic accuracy of a structured interview for nocturnal frontal lobe epilepsy (SINFLE): a proposal for developing diagnostic criteria

OBJECTIVES

To measure the accuracy of anamnestic features collected during clinical history for the diagnosis of nocturnal frontal lobe epilepsy (NFLE).

METHODS

A case-control diagnostic study. Participants included a case group of people with ascertained target disease (NFLE group) and a control group of people with sleep disorders potentially confounding for NFLS (NOT-NFLE group), defined by means of a consensus procedure among experts (panel diagnosis as reference standard). Two major clinical patterns defining the semeiology of the epileptic event (i.e. dystonic, DP, and/or hyperkinetic pattern, HP), and 13 additional minor features were identified, formulated as questions, and telephonically administered to NFLE and NOT-NFLE groups by a trained doctor blinded to the final diagnosis. The diagnostic accuracy of each characteristic was tested against the reference standard.

RESULTS

Out of 262 selected subjects, 101 were recruited; 42 were NFLE and 59 NOT-NFLE. A positive history of DP or HP had a sensitivity of 59.5% and a specificity of 91.5%, irrespective of the other minor anamnestic features. The anamnestic model improved, with a sensitivity of 59.5% and specificity of 96.6%, if at least one of the following four minor anamnestic features was added: (a) duration less than two minutes, (b) unstructured vocalization during the episode, (c) experience of an aura preceding the motor attack, and (d) a history of tonic-clonic seizures during sleep.

CONCLUSIONS

The present study disclosed two major anamnestic patterns and four minor features that we called SINFLE, with unsatisfactory sensitivity but high specificity. These patterns could be the basis for developing future NFLE diagnostic criteria and to quantify the diagnostic accuracy of elements usually collected in the clinical history.

NREM arousal parasomnias and their distinction from nocturnal frontal lobe epilepsy: a video EEG analysis

STUDY OBJECTIVES

To describe the semiological features of NREM arousal parasomnias in detail and identify features that can be used to reliably distinguish parasomnias from nocturnal frontal lobe epilepsy (NFLE).

DESIGN

Systematic semiologial evaluation of parasomnias and NFLE seizures recorded on video-EEG monitoring.

PATIENTS

120 events (57 parasomnias, 63 NFLE seizures) from 44 subjects (14 males). Interventions. The presence or absence of 68 elemental clinical features was determined in parasomnias and NFLE seizures. Qualitative analysis of behavior patterns and ictal EEG was undertaken. Statistical analysis was undertaken using established techniques.

RESULTS

Elemental clinical features strongly favoring parasomnias included: interactive behavior, failure to wake after event, and indistinct offset (all P < 0.001). Cluster analysis confirmed differences in both the frequency and combination of elemental features in parasomnias and NFLE. A diagnostic decision tree generated from these data correctly classified 94% of events. While sleep stage at onset was discriminatory (82% of seizures occurred during stage 1 or 2 sleep, with 100% of parasomnias occurring from stage 3 or 4 sleep), ictal EEG features were less useful. Video analysis of parasomnias identified three principal behavioral patterns: arousal behavior (92% of events); non-agitated motor behavior (72%); distressed emotional behavior (51%).

CONCLUSIONS

Our results broadly support the concept of confusion arousals, somnambulism and night terrors as prototypical behavior patterns of NREM parasomnias, but as a hierarchical continuum rather than distinct entities. Our observations provide an evidence base to assist in the clinical diagnosis of NREM parasomnias, and their distinction from NFLE seizures, on semiological grounds.

Intracerebral recordings of nocturnal hyperkinetic seizures: Demonstration of a longer duration of the pre-seizure sleep spindle

OBJECTIVE

Nocturnal frontal lobe epilepsy (NFLE) seizures occur primarily during non-rapid eye movement sleep stage 2. We observed in several patients rhythms of same localization and frequency as sleep spindles, immediately preceding and sometimes continuing at seizure onsets. We aimed to study the link between sleep spindles and seizure onsets.

METHODS

We used intracerebral stereo-EEG ictal recordings of two MRI-negative patients with clinically defined NFLE. For each of the six studied seizures, sustained activity in the frontal sleep spindle frequency (12Hz) was observed around seizure onset. The duration of this pre-seizure sleep spindle was compared to that of the 10 preceding sleep spindles.

RESULTS

The pre-seizure sleep spindles were clearly of longer duration than the "interictal" sleep spindles for all seizures. This sustained pre-seizure 12Hz activity could be differentiated from normal awakenings, and showed no spatial relation to the ictal onset.

CONCLUSIONS

We demonstrated a functional alteration of the sleep spindle-generating thalamocortical loop concomitant with the seizure onsets. This defect may also be involved in seizure generation.

SIGNIFICANCE

A thalamic participation in NFLE pathogenesis is likely in our two patients. The study of additional patients will allow to evaluate the role of the thalamocortical circuits in NFLE.

Movement disorders in sleep: guidelines for differentiating epileptic from non-epileptic motor phenomena arising from sleep

Seizures, namely in certain epileptic conditions, may be precipitated by sleep. Nocturnal frontal lobe epilepsy seizures, characterized by bizarre motor behaviour and autonomic activation, appear almost exclusively during sleep. The differential diagnosis between this condition and sleep-related non-epileptic paroxysmal motor phenomena, in particular the parasomnias, is arduous. Moreover, accepted criteria for the diagnosis of nocturnal frontal lobe seizures are lacking and even ictal scalp EEG recording could fail to disclose paroxysmal abnormalities. The clinical and polygraphic features of the different types of seizures in nocturnal frontal lobe epilepsy and of the more common non-epileptic paroxysmal events during sleep are described. The main differentiating features characterizing nocturnal frontal seizures are: onset at any age, several attacks per night at any time during the night, brief duration (s) with stereotyped motor pattern. As video-polysomnographic recordings of the attack, the gold-standard for diagnosis, are expensive and not readily available everywhere, home-made video recordings may be helpful. Further investigations on pathophysiology, genetics and epidemiology are needed to clarify the relationship between epileptic and non-epileptic sleep related paroxysmal phenomena.