The role of the amygdala in ictal central apnea: insights from brain MRI morphometry

OBJECTIVE

Ictal central apnea (ICA) is a frequent correlate of focal seizures, particularly in temporal lobe epilepsy (TLE), and regarded as a potential electroclinical biomarker of sudden unexpected death in epilepsy (SUDEP). Aims of this study are to investigate morphometric changes of subcortical structures in ICA patients and to find neuroimaging biomarkers of ICA in patients with focal epilepsy.

METHODS

We prospectively recruited focal epilepsy patients with recorded seizures during a video-EEG long-term monitoring with cardiorespiratory polygraphic recordings from April 2020 to September 2022. Participants were accordingly subdivided into two groups: patients with focal seizures with ICA (ICA) and without (noICA). A pool of 30 controls matched by age and sex was collected. All the participants underwent MRI scans with volumetric high-resolution T1-weighted images. Post-processing analyses included a whole-brain VBM analysis and segmentation algorithms performed with FreeSurfer.

RESULTS

Forty-six patients were recruited (aged 15-60 years): 16 ICA and 30 noICA. The whole-brain VBM analysis showed an increased gray matter volume of the amygdala ipsilateral to the epileptogenic zone (EZ) in the ICA group compared to the noICA patients. Amygdala sub-segmentation analysis revealed an increased volume of the whole amygdala, ipsilateral to the EZ compared to controls [F(1, 76) = 5.383, pFDR = 0.042] and to noICA patients ([F(1, 76) = 5.383, pFDR = 0.038], specifically of the basolateral complex (respectively F(1, 76) = 6.160, pFDR = 0.037; F(1, 76) = 5.121, pFDR = 0.034).

INTERPRETATION

Our findings, while confirming the key role of the amygdala in participating in ictal respiratory modifications, suggest that structural modifications of the amygdala and its subnuclei may be valuable morphological biomarkers of ICA.

Altered amygdala volumes and microstructure in focal epilepsy patients with tonic-clonic seizures, ictal, and post-convulsive central apnea

OBJECTIVES

Sudden unexpected death in epilepsy (SUDEP) is a leading cause of death for patients with epilepsy; however, the pathophysiology remains unclear. Focal-to-bilateral tonic-clonic seizures (FBTCS) are a major risk factor, and centrally-mediated respiratory depression may increase the risk further. Here, we determined the volume and microstructure of the amygdala, a key structure that can trigger apnea in people with focal epilepsy, stratified by the presence or absence of FBTCS, ictal central apnea (ICA), and post-convulsive central apnea (PCCA).

METHODS

Seventy-three patients with focal impaired awareness seizures without FBTC seizures (FBTCneg group) and 30 with FBTCS (FBTCpos group) recorded during video electroencephalography (VEEG) with respiratory monitoring were recruited prospectively during presurgical investigations. We acquired high-resolution T1-weighted anatomic and multi-shell diffusion images, and computed neurite orientation dispersion and density imaging (NODDI) metrics in all patients with epilepsy and 69 healthy controls. Amygdala volumetric and microstructure alterations were compared between three groups: healthy subjects, FBTCneg and FBTCpos groups. The FBTCpos group was further subdivided by the presence of ICA and PCCA, verified by VEEG.

RESULTS

Bilateral amygdala volumes were significantly increased in the FBTCpos cohort compared to healthy controls and the FBTCneg group. Patients with recorded PCCA had the highest increase in bilateral amygdala volume of the FBTCpos cohort. Amygdala neurite density index (NDI) values were decreased significantly in both the FBTCneg and FBTCpos groups relative to healthy controls, with values in the FBTCpos group being the lowest of the two. The presence of PCCA was associated with significantly lower NDI values vs the non-apnea FBTCpos group (p = 0.004).

SIGNIFICANCE

Individuals with FBTCpos and PCCA show significantly increased amygdala volumes and disrupted architecture bilaterally, with greater changes on the left side. The structural alterations reflected by NODDI and volume differences may be associated with inappropriate cardiorespiratory patterns mediated by the amygdala, particularly after FBTCS. Determination of amygdala volumetric and architectural changes may assist identification of individuals at risk.

CLINICAL CASE OF THE INNATE CENTRAL HYPOVENTILATION SYNDROME IN THE PARTURIENT

The syndrome "of the curse of Undina" or the innate central hypoventilation syndrome with the second disorder of cen- tral nervous system is the result of the disrupted vegetative control of the respiration in the absence of neuromuscular diseases and disturbances of the mechanics of respiration. In the clinical practice diagnostics of this state is complex, frequently the cases remain not diagnosed. Taking into account clinical manifestations and depending on the degree of their intensity, early diagnostics, which warns the undesirable consequences ofthe episodes ofhypoxia and hypercapnia, that ensures the proper checking of the episodes of asphyxia, determines not only the forecast of disease, but also life of patient. The purpose ofthis work is the idea of the clinical case of this rarely meeting illness.

Central sleep apnea in children: experience at a single center

OBJECTIVE

Central sleep apnea (CSA) syndromes are rare in children and data in children over one year of age are scarce. The aim of the study was to describe the sleep characteristics, underlying disorders, management, and outcome of children with CSA.

PATIENTS/METHODS

A retrospective chart review of all children >1 year of age, diagnosed with CSA on a laboratory sleep study during a 20-month period, was performed. CSA was defined by a central apnea index (CAI) >5 events/h. The clinical management and the patient's outcome were analyzed.

RESULTS

Eighteen of 441 (4.1%) patients recorded during the study period had CSA. The median CAI, pulse oximetry, and oxygen desaturation index were 13/h (range 6-146), 96% (93-98%), and 18/h (6-98), respectively. Neurosurgical pathologies represented the most common underlying disorders with Arnold-Chiari malformation in four and ganglioglioma in three patients. Other underlying disorders were Prader-Willi syndrome (N = 3), achondroplasia (N = 2), and Down syndrome, with one patient having an achondroplasia and a Down syndrome. The remaining six patients had other genetic diseases. The most common investigation was brain magnetic resonance imaging (MRI). Individualized management with neurosurgery and/or chemotherapy, continuous positive airway pressure (in two patients having associated obstructive events), or noninvasive ventilation resulted in an improvement in CSA and the clinical presentation in 11 patients.

CONCLUSION

CSA is rare in children >1 year of age. Underlying disorders are dominated by neurosurgical disorders. Individualized management is able to improve CSA and the clinical condition in most patients.

Left atrial size, chemosensitivity, and central sleep apnea in heart failure

BACKGROUND

Central sleep apnea (CSA) is common among patients with heart failure (HF) and is promoted by elevated CO2 chemosensitivity. Left atrial size is a marker of the hemodynamic severity of HF. The aim of this study was to determine if left atrial size predicts chemosensitivity to CO2 and CSA in patients with HF.

METHODS

Patients with HF with left ventricular ejection fraction ≤ 35% underwent polysomnography for detection of CSA, echocardiography, and measurement of CO2 chemosensitivity. CSA was defined as an apnea-hypopnea index (AHI) ≥ 15/h with ≥ 50% central apneic events. The relation of clinical and echocardiographic parameters to chemosensitivity and CSA were evaluated by linear regression, estimation of ORs, and receiver operator characteristics.

RESULTS

Of 46 subjects without OSA who had complete data for analysis, 25 had CSA. The only parameter that significantly correlated with chemosensitivity was left atrial volume index (LAVI) (r = 0.40, P < .01). LAVI was greater in those with CSA than those without CSA (59.2 mL/m2 vs 36.4 mL/m2, P < .001) and significantly correlated with log-transformed AHI (r = 0.46, P = .001). LAVI was the best predictor of CSA (area under the curve = 0.83). A LAVI ≤ 33 mL/m2 was associated with 22% risk for CSA, while LAVI ≥ 53 mL/m2 was associated with 92% risk for CSA.

CONCLUSIONS

Increased LAVI is associated with heightened CO2 chemosensitivity and greater frequency of CSA. LAVI may be useful to guide referral for polysomnography for detection of CSA in patients with HF.

Effect of adaptive servoventilation on muscle sympathetic nerve activity in patients with chronic heart failure and central sleep apnea

BACKGROUND

Adaptive servoventilation (ASV) improves cardiac function and sympathetic nerve activity in patients with heart failure (HF). However, the mechanisms underlying these improvements remain obscure.

METHODS AND RESULTS

We compared muscle sympathetic nerve activity (MSNA) and cardiorespiratory polygraphy and echocardiography findings at baseline and at 3.5 ± 0.8 months' follow-up in 32 patients with HF (New York Heart Association functional class II or III; ejection fraction <45%) and central sleep apnea (CSA; apnea-hypopnea index [AHI] ≥15/h) who consented (n = 20; ASV group) or declined (n = 12; non-ASV group) to undergo ASV treatment. Compliance with ASV and changes in AHI were determined from data collected by integral counters in devices and from cardiorespiratory polygraphic findings, respectively. Ejection fraction and MSNA significantly changed in the ASV (both P < .001) but not the non-ASV group. Although changes in AHI and MSNA correlated, the average use of ASV did not. In contrast, changes in AHI and the average use of ASV were independent predictors of changes in ejection fraction (both P < .01).

CONCLUSIONS

ASV decreases MSNA and improves cardiac function in association with suppression of CSA in patients with HF.

Characteristics of sleep-disordered breathing in Japanese patients with type 2 diabetes mellitus

Sleep-disordered breathing (SDB), especially sleep apnea-hypopnea syndrome, is often observed in patients with type 2 diabetes mellitus; but there are only a few studies on SDB in Japanese diabetic subjects. We investigated the prevalence of SDB in diabetic patients; associations between severity of sleep apnea (SA) and clinical factors, visceral fat, and adiponectin; and associations between type of SA and clinical factors. In the present study, 40 Japanese diabetic patients underwent overnight cardiorespiratory monitoring, and night and morning measurements of serum adiponectin concentrations. Sleep apnea was detected in Japanese diabetic patients at a high prevalence (77.5%). The following variables were associated with SDB: age, body mass index, estimated visceral fat area, and nocturnal reduction in serum adiponectin concentrations. The prevalence of central sleep apnea (CSA, >or=5/h) was 32.3% among diabetic SDB patients. Diabetic SDB patients with CSA had higher hemoglobin, increased intima-media thickness, and higher plasma brain natriuretic peptide levels than those without CSA (<5/h). In conclusion, our study demonstrated a high prevalence of SDB in Japanese diabetic patients, which correlated with visceral fat area and adiponectin. A high frequency of CSA was noted in diabetic SDB patients, together with high hemoglobin, high brain natriuretic peptide, and increased intima-media thickness. The present results of prevalence of SDB may be relevant to the higher incidence of cardiovascular disease in diabetic patients, which need to be clarified in future studies.

Assessment of central chemosensitivity and cardiac sympathetic nerve activity using I-123 MIBG imaging in central sleep apnea syndrome in patients with dilated cardiomyopathy

OBJECTIVE

Iodine-123 MIBG imaging has been used to study cardiac sympathetic function in various cardiac diseases. Central sleep apnea syndrome (CSAS) occurs frequently in patients with chronic heart failure (CHF) and is reported to be associated with a poor prognosis. One of the mechanisms of its poor prognosis may be related to impaired cardiac sympathetic activity. However, the relationship between chemosensitivity to carbon dioxide, which is reported to correlate with the severity of CSAS, and cardiac sympathetic activity has not been investigated. Therefore, this study was undertaken to assess cardiac sympathetic function and chemosensitivity to carbon dioxide in CHF patients.

METHODS

The oxygen desaturation index (ODI) was evaluated in 21 patients with dilated cardiomyopathy (male/female: 19/2, LVEF < 45%, 65 +/- 12 yr). Patients with an ODI > 5 times/h underwent polysomnography. Patients with an apnea hypopnea index > 15/h but without evidence of obstructive apnea were defined as having CSAS. Early (15 min) and delayed (4 hr) planar MIBG images were obtained from these patients. The mean counts in the whole heart and the mediastinum were obtained. The heart-to-mediastinum count ratio of the delayed image (H/M) and the corrected myocardial washout rate (WR) were also calculated. The central chemoreflex was assessed with the rebreathing method using a hypercapnic gas mixture (7% CO2 and 93% O2).

RESULTS

Ten of the 21 patients had CSAS. The H/M ratio was similar in patients both with and without CSAS (1.57 +/- 0.18 vs. 1.59 +/- 0.14, p = 0.82). However, the WR was higher in patients with CSAS than in patients without CSAS (40 +/- 8% vs. 30 +/- 12%, p < 0.05). ODI significantly correlated with central chemosensitivity to carbon dioxide. Moreover, there was a highly significant correlation between WR and central chemosensitivity (r = 0.65, p < 0.05). However, there was no correlation between ODI and the WR (r = 0.36, p = 0.11).

CONCLUSIONS

Cardiac sympathetic nerve activity in patients with CHF and CSAS is impaired. However, central sleep apnea might not directly increase cardiac sympathetic nerve activity. We suggest that central chemosensitivity, which is considered to be one of the mechanisms of CSAS, is correlated with cardiac sympathetic nerve activity.