Structural Brain Correlates of Sleep Microstructure in Spinocerebellar Ataxia Type 2 and its Role on Clinical Phenotype

The influence of brain atrophy on sleep microstructure in Spinocerebellar Ataxias (SCAs) has not been extensively explored limiting the use of these sleep traits as surrogate biomarkers of neurodegeneration and clinical phenotype. The objective of the study is to explore the relationship between sleep microstructure and brain atrophy in SCA2 and its role in the clinical phenotype. Fourteen SCA2 mutation carriers (7 pre-manifest and 7 manifest subjects) underwent polysomnographic, structural MRI, and clinical assessments. Particularly, markers of REM and non-REM sleep microstructure, measures of cerebellar and brainstem atrophy, and clinical scores were analyzed through correlation and mediation analyses. The sleep spindle activity exhibited a negative correlation with the number of trials required to complete the verbal memory test (VMT), and a positive correlation with the cerebellar volume, but the significance of the latter correlation did not survive multiple testing corrections. However, the causal mediation analyses unveiled that sleep spindle activity significantly mediates the association between cerebellar atrophy and VMT performance. Regarding REM sleep, both phasic EMG activity and REM sleep without atonia exhibited significant associations with pontine atrophy and disease severity measures. However, they did not demonstrate a causal mediation effect between the atrophy measures and disease severity. Our study provides evidence about the association of the pontocerebellar atrophy with sleep microstructure in SCA2 offering insights into the cerebellar involvement in cognition via the control of the sleep spindle activity. Therefore, our findings may help to understand the disease pathogenesis and to better characterize sleep microstructure parameters as disease biomarkers.Clinical trial registration number (TRN): No applicable.

Sleep spindle activity is associated with state- and trait-based emotion in healthy school-aged children

BACKGROUND

While connections between children's sleep and their daytime functioning are well established, less is known about the microstructural features of sleep that support emotional wellbeing. Investigating these relationships in healthy children may provide insight into adaptive emotional development. We therefore examined associations between non-rapid eye movement (N2) sleep spindles and both state- and trait-based measures of emotion.

METHODS

A sample of 30 children (7-11 years) without psychiatric disorders completed a baseline assessment, one night of at-home polysomnography (PSG), and an in-lab emotional state assessment the next day including self-reported arousal in response to affective images. Trait-based measures of anxiety and depression as well as savoring, a positive emotion regulatory strategy, were also completed. N2 sleep spindle parameters, including spindle density (number/min) and peak frequency in central regions, were detected using an automated algorithm.

RESULTS

Greater spindle density was significantly associated with decreased state-based emotional arousal towards negative affective images, and greater spindle peak frequency was associated with greater trait-based use of savoring. However, neither spindle parameter was associated with child anxiety or depressive symptoms.

CONCLUSIONS

Findings align with and expand on prior research to suggest that N2 sleep spindles support adaptive emotional functioning in school-aged children.

Electroencephalographic slowdowns during sleep are associated with cognitive impairment in patients who have obstructive sleep apnea but no dementia

OBJECTIVES

To research the relationship between quantitative electroencephalogram (qEEG) and impaired cognitive function patients who have obstructive sleep apnea (OSA) but no dementia.

METHODS

Subjects who complained of snoring between March 2020 and April 2021 in the Sleep Medicine Center of Weihai Municipal Hospital were included. All subjects underwent overnight in-laboratory polysomnography (PSG) and were assessed using a neuropsychological scale. Standard fast fourier transform (FFT) was used to obtain the electroencephalogram (EEG) power spectral density curve, and to calculate the delta, theta, alpha, and beta relative power and the ratio between slow and fast frequencies. Binary logistic regression was used to assess the risk factors for cognitive impairment in patients who had OSA but no dementia. Correlation analysis was performed to determine the relationship between qEEG and cognitive impairment.

RESULTS

A total of 175 participants without dementia who met the inclusion criteria were included in this study. There were 137 patients with OSA, including 76 with mild cognitive impairment (OSA + MCI), 61 without mild cognitive impairment (OSA-MCI), and 38 participants without OSA (non-OSA). The relative theta power in the frontal lobe in stage 2 of non-rapid eye movement sleep (NREM 2) in OSA + MCI was higher than that in OSA-MCI (P = 0.038) and non-OSA (P = 0.018). Pearson correlation analysis showed that the relative theta power in the frontal lobe in NREM 2 was negatively correlated with Mini-Mental State Examination (MMSE) scores, Montreal Cognitive Assessment (MoCA) Beijing version scores, and MoCA subdomains scores (visual executive function, naming, attention, language, abstraction, delayed recall and orientation) outside language.

CONCLUSIONS

In patients who had OSA but no dementia, the EEG slower frequency power increased. The relative theta power in the frontal lobe in NREM 2 was associated with MCI of patients with OSA. These results suggest that the slowing of theta activity may be one of the neurophysiological changes in the early stage of cognitive impairment in patients with OSA.

Association of neurocognitive functioning with sleep stage dissociation and REM sleep instability in medicated patients with schizophrenia

Many patients with schizophrenia present with impaired cognitive functioning and sleep disturbances. Dissociated stages of sleep represent instability within distinct sleep regulatory cerebral networks. Previous studies found increased rates of rapid eye movement (REM) sleep abnormalities in patients with schizophrenia and a positive association with psychopathology. In this study, we examined if sleep stage dissociation and REM sleep instability was associated with neurocognitive functioning in a sample of medicated patients with schizophrenia. The analyses were performed on 31 baseline polysomnographic recordings as well as baseline data on neurocognitive performance. Regression models were built with the cognitive composite score as primary dependent variable and measures of sleep stage dissociation, including REM sleep without atonia (RSWA), REM sleep without eye movements, non-REM sleep with eye movements, REM sleep percentage in REM periods and REM sleep stability as independent variables. Analyses were adjusted for age, gender, total antipsychotic dose, total benzodiazepine dose, and symptom severity. After correction for multiple testing, we found that the neurocognitive composite score was inversely associated with the degree of RSWA. Exploratory analyses with the cognitive sub scores as dependent variables showed that RSWA was associated with cognitive performance across several sub domains. Dissociated sleep stages, specifically the RSWA feature, might represent a new treatment target for improving cognitive impairment in patients with schizophrenia.

Reduced sleep spindle activity in children with primary snoring

BACKGROUND

Habitually snoring children are at risk of manifesting disease-related problems even if their sleep studies are overall within normal limits.

STUDY OBJECTIVES

To compare sleep spindle activity in children with primary snoring and healthy controls.

METHODS

Sleep spindle activity including analysis of fast and slow spindles (ie, >13 Hz and <13 Hz, respectively) was evaluated in polysomnographic (PSG) recordings of 20 randomly selected children with primary snoring (PS; normal PSG recordings except for objective presence of snoring; 12 boys, mean age 6.5 ± 2.1 years), and 20 age- and gender-matched PSG-confirmed non-snoring controls.

RESULTS

PS children showed significantly lower spindle indices in all non-rapid eye movement (NREM) sleep stages (p < 0.05). In contrast, fast spindles were found in 40% (n = 8) children with PS and in 25% (n = 5) controls. Sleep spindle activity was particularly higher in NREM sleep stage 2 in controls compared PS (76% versus 43% of all marked sleep spindles events in NREM sleep stage 2, p < 0.001).

CONCLUSIONS

Children with PS exhibit significantly reduced spindle activity when compared to matched controls. Reduced sleep spindle activity may be an indicator of sleep disruption and, therefore, could be involved in the development of disease-related consequences in snoring children.

Sleep spindle activity in children with obstructive sleep apnea as a marker of neurocognitive performance: A pilot study

STUDY OBJECTIVES

To assess spindle activity as possible markers for neurocognitive consequences in children with mild obstructive sleep apnea.

METHODS

Children aged 6-11 years diagnosed with mild OSA (i.e., an apnea hypopnea index <5.0) were recruited and compared with age and gender-matched healthy controls. Polysomnographic recordings were analyzed for sleep microstructure and spindle activity. All children completed also an intelligence test battery (i.e., the Wechsler intelligence test for children, 4th version).

RESULTS

Nineteen children with OSA (13 boys, mean age 7.1 ± 1.4 y), and 14 controls (7 boys, mean age 8.1 ± 1.9 y) were included. Mean IQ was 110 ± 12 for the complete sample, in children with OSA 111 ± 13, and in controls 108 ± 12 (p = 0.602). Controls showed a higher spindle index in N2 stage than children with OSA: 143.0 ± 42.5 vs 89.5 ± 56.9, respectively (p = 0.003). Spindle index in NREM was strongly and significantly correlated with Verbal Comprehension Index (VCI), Working Memory Index (WMI), Processing Speed Index (PSI), and total IQ in children with OSA.

CONCLUSIONS

Children with mild OSA demonstrate a different pattern of sleep spindle activity that seems to be linked with neurocognitive performance, especially concerning memory. Sleep spindle activity seems to be involved with mechanisms related with neurocognitive consequences in children with OSA.

Study of sleep microstructure in patients of migraine without aura

PURPOSE

Although the relationship between sleep and migraine has been widely reported, studies on sleep microstructure are few. The aim was to study and compare microstructural polysomnographic characteristics in patients of "migraine without aura" (MOA) with controls.

METHODS

Twenty-five patients of MOA and 25 age- and gender-matched healthy controls were subjected to overnight polysomnography. Microstructural sleep analysis, including arousal and cyclic alternating pattern (CAP) analysis was performed. Arousals and CAP parameters were compared between the two groups using the Mann-Whitney U test (p ≤ 0.05).

RESULTS

The overall arousal index (p = 0.528) and that during non-rapid eye movement (NREM) sleep (p = 0.503) were comparable between the two groups. However, the arousal index was lower in migraineurs during rapid eye movement (REM) sleep (p = 0.001). The overall CAP rate (p = 0.020) as well as the number of CAP cycles and sequences (p = 0.032) was lower among migraineurs. The total phase A duration (p < 0.0001) was increased, and conversely, phase B duration (p = 0.001) was decreased in migraineurs. The phase A1 duration (p = 0.036) was higher in migraineurs. Finally, phase A1 (p = 0.357) index was comparable, and conversely, A2 (p < 0.0001) and A3 (p = 0.020) indices were decreased in migraineurs.

CONCLUSIONS

This study showed a decreased REM arousability as well as a decreased overall CAP rate and CAP cycling in patients with migraine as compared to controls. This indicates that there is probably an alteration of the arousal mechanisms in patients with migraine that may facilitate the occurrence of headache paroxysms during sleep.

EEG segmentation for improving automatic CAP detection

OBJECTIVE

The aim of this study is to provide an improved method for the automatic classification of the Cyclic Alternating Pattern (CAP) sleep by applying a segmentation technique to the computation of descriptors from the EEG.

METHODS

A dataset of 16 polysomnographic recordings from healthy subjects was employed, and the EEG traces underwent first an automatic isolation of NREM sleep portions by means of an Artificial Neural Network and then a segmentation process based on the Spectral Error Measure. The information content of the descriptors was evaluated by means of ROC curves and compared with that of descriptors obtained without the use of segmentation. Finally, the descriptors were used to train a discriminant function for the automatic classification of CAP phases A.

RESULTS

A significant improvement with respect to previous scoring methods in terms of both information content carried by the descriptors and accuracy of the classification was obtained.

CONCLUSIONS

EEG segmentation proves to be a useful step in the computation of descriptors for CAP scoring.

SIGNIFICANCE

This study provides a complete method for CAP analysis, which is entirely automatic and allows the recognition of A phases with a high accuracy thanks to EEG segmentation.