Sleep-Disordered Breathing is frequently associated with idiopathic normal pressure hydrocephalus but not other types of hydrocephalus

Cerebrospinal-fluid Orexin-A levels in different neurocognitive disorders: a comparison study

In the present study, we investigated the differences in cerebrospinal fluid (CSF) orexin-A levels among patients with different neurocognitive disorders, such as mild or moderate to severe Alzheimer's disease (AD; mAD, msAD, respectively), behavioral variants of frontotemporal dementia (bv-FTD), non-fluent primary aphasia (NFPA), and idiopathic normal pressure hydrocephalus (iNPH). A total of 214 participants were evaluated (mAD, 45; msAD, 31; bv-FTD, 12; NFPA, 22; iNPH, 13; non-demented elderly controls, 91). The highest CSF orexin-A levels were found in iNPH patients (263.31 ± 56.89 pg/mL). Patients affected by NFPA (210.86 ± 61.99 pg/mL), iNPH, and msAD (173.04 ± 19.76 pg/mL) showed higher CSF orexin-A concentrations than controls (145.18 ± 27.01pg/mL) (p < 0.001). Bv-FTD (190.12 ± 100.84 pg/mL) and mAD (130.76 ± 21.70 pg/mL) patients showed no significant differences in CSF orexin-A levels compared with controls. mAD patients showed also lower CSF orexin-A concentrations than all other patient groups.In conclusion, orexin-A presents different CSF levels among neurocognitive disorders. The mechanisms underlying this difference vary and may include sleep-wake cycle impairment, behavioral disturbances, and CSF dynamics. The development of drugs that antagonize the orexin system could open a new frontier of research linking orexin neurotransmission to neurocognitive disorders.

Decrease of excessive daytime sleepiness after shunt treatment for normal pressure hydrocephalus

Sleepiness and apathy are often reported in patients with normal pressure hydrocephalus. However, research on outcomes after shunt surgery has mainly focused on the classical triad symptoms, that is, gait, cognition, and bladder dysfunction. This study aimed to describe the effects of shunt treatment on excessive daytime sleepiness and whether there was a relation to changes in ventricular volume. Pre- and postsurgical excessive daytime sleepiness was investigated using the Epworth sleepiness scale in a sample of 32 patients with normal pressure hydrocephalus who underwent shunt surgery. Data were gathered before surgery and at 1, 2, and 3 months after surgery and with different settings of the shunt. In the total sample, the Epworth sleepiness scale improved by a median of 1.5 points at 1 month after surgery, p = 0.026. The improvement was predominately found in the group (n = 6) with high presurgical daytime sleepiness (Epworth sleepiness scale >12) (median = 12 points, p = 0.035) compared with a median change of 0 points (p = 0.47) in the group with Epworth sleepiness scale ≤12 (n = 26). Between the postsurgical follow-ups, no further change in the Epworth sleepiness scale score was observed. The Epworth sleepiness scale score did not correlate with clinical tests nor with ventricular volume. Daytime sleepiness seems to be another domain of normal pressure hydrocephalus symptomatology in addition to the classical triad that is responsive to treatment, at least when pronounced. The Epworth sleepiness scale is a quick test to administer and could be a valuable addition to pre-surgical screening for treatable symptoms.

In response to Mutti et al. 2024 commentary on "Transient intracranial pressure elevations (B waves) associated with sleep apnea: the neglected role of cyclic alternating pattern"

The physiology of transient intracranial pressure (ICP) elevations (B waves), remains incompletely understood and appears to involve multiple mechanisms, including obstructive sleep apnea (OSA). Transient ICP elevations are associated with OSA and cyclic alternating pattern (CAP) metrics, suggesting a complex interplay between sleep fragmentation and ICP dynamics. Additionally, CAP metrics could complement standard OSA assessments, providing deeper insights into transient ICP fluctuations, particularly in conditions like normal-pressure hydrocephalus and idiopathic intracranial hypertension. Future studies should explore CAP-ICP interactions to elucidate their physiological and clinical implications.

Clinical correlates of obstructive sleep apnoea in idiopathic normal pressure hydrocephalus

BACKGROUND AND PURPOSE

The pathogenesis of idiopathic normal pressure hydrocephalus (iNPH) remains controversial. Limited studies have indicated a high prevalence of obstructive sleep apnoea (OSA) amongst iNPH patients. The aim was to investigate the clinical correlates of OSA in iNPH patients.

METHODS

In this cross-sectional observational study, consecutive iNPH patients were prospectively enrolled. Evaluations included the iNPH Rating Scale, the Movement Disorder Society Unified Parkinson's Disease Rating Scale part III, the time and number of steps to walk 10 m, the Epworth Sleepiness Scale, the Pittsburgh Sleep Quality Index, a complete neuropsychological evaluation, 3-T brain MRI, full-night video-polysomnography, tap test and cerebrospinal fluid (CSF) neurodegeneration biomarkers.

RESULTS

Fifty-one patients were screened, of whom 38 met the inclusion criteria. Amongst the recruited patients, 19/38 (50%) exhibited OSA, with 12/19 (63.2%) presenting moderate to severe disorder. OSA+ iNPH patients required more time (p = 0.02) and more steps (p = 0.04) to complete the 10-m walking test, had lower scores on the gait subitem of the iNPH Rating Scale (p = 0.04) and demonstrated poorer performance on specific neuropsychological tests (Rey Auditory Verbal Learning Test immediate recall, p = 0.03, and Rey-Osterrieth Complex Figure, p = 0.01). Additionally, OSA+ iNPH patients had higher levels of total tau (p = 0.02) and phospho-tau (p = 0.03) in their CSF but no statistically significant differences in beta-amyloid (1-42) levels compared to OSA- iNPH patients.

CONCLUSION

Obstructive sleep apnoea is highly prevalent in iNPH patients, particularly at moderate to severe levels. OSA is associated with worse motor and cognitive performance in iNPH. The CSF neurodegeneration biomarker profile observed in OSA+ iNPH patients may reflect OSA-induced impairment of cerebral fluid dynamics.

Transient intracranial pressure elevations (B waves) are associated with sleep apnea

BACKGROUND

Repetitive transient intracranial pressure waveform elevations up to 50 mmHg (ICP B-waves) are often used to define pathological conditions and determine indications for ICP-reducing treatment. We recently showed that nocturnal transient ICP elevations are present in patients without structural brain lesions or hydrocephalus in whom they are associated with sleep apnea. However, whether this signifies a general association between ICP macropatterns and sleep apnea remains unknown.

METHODS

We included 34 patients with hydrocephalus, or idiopathic intracranial hypertension (IIH), who were referred to the Neurosurgical Department, Copenhagen, Denmark, from 2017 to 2021. Every patient underwent diagnostic overnight ICP monitoring for clinical indications, with simultaneous polysomnography (PSG) sleep studies. All transient ICP elevations were objectively quantified in all patients. Three patients were monitored with continuous positive airway pressure (CPAP) treatment for an additional night.

RESULTS

All patients had transient ICP elevations associated with sleep apnea. The mean temporal delay from sleep apnea to transient ICP elevations for all patients was 3.6 s (SEM 0.2 s). Ramp-type transient ICP elevations with a large increase in ICP were associated with rapid eye movement (REM) sleep and sinusoidal-type elevations with non-REM (NREM) sleep. In three patients treated with CPAP, the treatment reduced the number of transient ICP elevations with a mean of 37%. CPAP treatment resulted in insignificant changes in the average ICP in two patients but elevated the average ICP during sleep in one patient by 5.6 mmHg.

CONCLUSION

The findings suggest that sleep apnea causes a significant proportion of transient ICP elevations, such as B-waves, and sleep apnea should be considered in ICP evaluation. Treatment of sleep apnea with CPAP can reduce the occurrence of transient ICP elevations. More research is needed on the impact of slow oscillating mechanisms on transient ICP elevations during high ICP and REM sleep.

Age-Related Changes in Cerebrospinal Fluid Dynamics in the Pathogenesis of Chronic Hydrocephalus in Adults

Cerebrospinal fluid (CSF) dynamics has dramatically changed in this century. In the latest concept of CSF dynamics, CSF is thought to be produced mainly from interstitial fluid excreted from the brain parenchyma and is absorbed in the meningeal lymphatics. Moreover, CSF does not always flow from the ventricles to the subarachnoid space unidirectionally through the foramina of Magendie and Luschka. In an environment of increased intracranial CSF in idiopathic normal pressure hydrocephalus, CSF freely moves through the inferior choroidal point of the choroidal fissure, which interfaces between the inferior horn of the lateral ventricles and the ambient cistern and through the velum interpositum between the third ventricle and the quadrigeminal cistern. The structure of the hippocampus adjacent to the inferior part of the choroidal fissure may be important in preventing the accumulation of waste products in the hippocampus. A recent imaging technology for CSF dynamics, such as four-dimensional flow and intravoxel incoherent motion magnetic resonance imaging, can visualize and quantify the pulsatile complex CSF motion in clinical usage. We present the current concepts of CSF dynamics with advanced magnetic resonance imaging techniques, which will be helpful in the management and understanding of the pathogenesis of chronic hydrocephalus in adults.

Physical Capacity and Activity in Patients With Idiopathic Normal Pressure Hydrocephalus

Introduction

Most patients with idiopathic normal pressure hydrocephalus (iNPH) improve gait after surgery. However, knowledge on physical capacity and activity after shunt surgery is limited. One of the aims of this study was to evaluate the effect of shunt surgery in patients with iNPH on short-distance walking, functional exercise capacity, functional strength, and variables of activity and sleep, 3 and 6 months postoperatively. Another aim was to evaluate the effect of a physical exercise program. Additionally, we studied how changes in short-distance walking were correlated with functional exercise capacity and voluntary walking.

Methods

In total, 127 patients were consecutively included and randomized to the exercise group (n = 62) or the control group (n = 65). Participants in the exercise group underwent the supervision of a 12-week exercise program. All patients were assessed before surgery, at 3 and 6 months postoperatively with the 10-m walk test (10MWT), the 6-min walk test (6MWT), 30-s chair stand test (30sCST), and with the actigraphic recordings of activity variables measured for a total of 24 h/day for at least 3 days.

Results

All patients improved at 3 months postoperatively in the 10MWT (p < 0.001), 6MWT (p < 0.001), and 30sCST (p < 0.001). These results were maintained after 6 months. Actigraphic recordings for voluntary walking (steps per minute) were improved and nighttime sleep (%) increased after 6 months (p = 0.01, p = 0.04). There were no significant differences between the exercise group and the control group, except for the postoperative change in the proportion of daytime sleep after 3 months, which was slightly more reduced compared to baseline in the exercise group (p = 0.04). Changes after 3 months in the 10MWT and 6MWT were moderately correlated (ρ= −0.49, p = 0.01) whereas the correlation between the 10MWT and voluntary walking was weak (ρ = −0.34, p = 0.01).

Conclusion

Shunt surgery improved short-distance walking, functional exercise capacity, functional strength, and voluntary walking. An exercise program did not affect these outcomes. Short-distance walking was weakly correlated with voluntary walking, indicating improved physical capacity does not directly translate to increased physical activity. Further research should address how interventions should be tailored to promote physical activity after shunt surgery.

Trial Registration

clinicaltrials.gov, Id: NCT02659111.