CSF markers of neurodegeneration Alzheimer's and Lewy body pathology in isolated REM sleep behavior disorder.

We investigated the biomarker profile of neurodegeneration, Alzheimer's and Lewy body pathology in the CSF of 148 polysomnography-confirmed patients with isolated REM sleep behavior disorder (IRBD), a condition that precedes Parkinson's disease (PD) and dementia with Lewy bodies (DLB). We assessed misfolded α-synuclein (AS) by RT-QuIC assay, amyloid-beta peptides (Aß42 and Aß40), phosphorylated tau (p-tau), and total tau (t-tau) by CLEIA and neurofilament light chain (NfL) by ELISA. We detected AS in 75.3% of patients, pathologically decreased Aß42/Aß40 ratio in 22.5%, increased p-tau in 15.5%, increased t-tau in 14.9%, and elevated NfL in 14.7%. After a mean follow-up of 2.48 ± 2.75 years, 47 (38.1%) patients developed PD (n = 24) or DLB (n = 23). At CSF collection, AS positivity [HR 4.05 (1.26-12.99), p = 0.019], mild cognitive impairment [3.86 (1.96-7.61), p < 0.001], and abnormal DAT-SPECT [2.31 (1.09-4.91), p < 0.030] were independent predictors of conversion to PD and DLB. Among the other CSF markers, only elevated p-tau/Aß42 was predictive of conversion, although only to DLB and not as an independent variable. In IRBD, CSF AS assessment by RT-QuIC provides an added value in defining the risk of short-term conversion to PD and DLB independent of clinical and instrumental investigations. Positive Alzheimer's disease (AD) pathology markers and elevated NfL occur in a subgroup of patients, but p-tau/Aß42 is the only marker that predicts short-term conversion to DLB. Longer follow-up is needed to assess if AD biomarkers predict the later development of PD and DLB in IRBD.

Locus coeruleus integrity and neuropsychiatric symptoms in a cohort of early- and late-onset Alzheimer's disease.

INTRODUCTION: Early-onset Alzheimer's disease (EOAD) shows a higher burden of neuropsychiatric symptoms than late-onset Alzheimer's disease (LOAD). We aim to determine the differences in the severity of neuropsychiatric symptoms and locus coeruleus (LC) integrity between EOAD and LOAD accounting for disease stage. METHODS: One hundred four subjects with AD diagnosis and 32 healthy controls were included. Participants underwent magnetic resonance imaging (MRI) to measure LC integrity, measures of noradrenaline levels in cerebrospinal fluid (CSF) and Neuropsychiatric Inventory (NPI). We analyzed LC-noradrenaline measurements and clinical and Alzheimer's disease (AD) biomarker associations. RESULTS: EOAD showed higher NPI scores, lower LC integrity, and similar levels of CSF noradrenaline compared to LOAD. Notably, EOAD exhibited lower LC integrity independently of disease stage. LC integrity negatively correlated with neuropsychiatric symptoms. Noradrenaline levels were increased in AD correlating with AD biomarkers. DISCUSSION: Decreased LC integrity negatively contributes to neuropsychiatric symptoms. The higher LC degeneration in EOAD compared to LOAD could explain the more severe neuropsychiatric symptoms in EOAD. HIGHLIGHTS: LC degeneration is greater in early-onset AD (EOAD) compared to late-onset AD. Tau-derived LC degeneration drives a higher severity of neuropsychiatric symptoms. EOAD harbors a more profound selective vulnerability of the LC system. LC degeneration is associated with an increase of cerebrospinal fluid noradrenaline levels in AD.

Mitochondrial DNA deletions in the cerebrospinal fluid of patients with idiopathic REM sleep behaviour disorder.

BACKGROUND: Idiopathic rapid eye movement (REM) sleep behaviour disorder (IRBD) represents the prodromal stage of Lewy body disorders (Parkinson's disease (PD) and dementia with Lewy bodies (DLB)) which are linked to variations in circulating cell-free mitochondrial DNA (cf-mtDNA). Here, we assessed whether altered cf-mtDNA release and integrity are already present in IRBD. METHODS: We used multiplex digital PCR (dPCR) to quantify cf-mtDNA copies and deletion ratio in cerebrospinal fluid (CSF) and serum in a cohort of 71 participants, including 1) 17 patients with IRBD who remained disease-free (non-converters), 2) 34 patients initially diagnosed with IRBD who later developed either PD or DLB (converters), and 3) 20 age-matched controls without IRBD or Parkinsonism. In addition, we investigated whether CD9-positive extracellular vesicles (CD9-EVs) from CSF and serum samples contained cf-mtDNA. FINDINGS: Patients with IRBD, both converters and non-converters, exhibited more cf-mtDNA with deletions in the CSF than controls. This finding was confirmed in CD9-EVs. The high levels of deleted cf-mtDNA in CSF corresponded to a significant decrease in cf-mtDNA copies in CD9-EVs in both IRBD non-converters and converters. Conversely, a significant increase in cf-mtDNA copies was found in serum and CD9-EVs from the serum of patients with IRBD who later converted to a Lewy body disorder. INTERPRETATION: Alterations in cf-mtDNA copy number and deletion ratio known to occur in Lewy body disorders are already present in IRBD and are not a consequence of Lewy body disease conversion. This suggests that mtDNA dysfunction is a primary molecular mechanism of the pathophysiological cascade that precedes the full clinical motor and cognitive manifestation of Lewy body disorders. FUNDING: Funded by Michael J. Fox Foundation research grant MJFF-001111. Funded by MICIU/AEI/10.13039/501100011033 "ERDF A way of making Europe", grants PID2020-115091RB-I00 (RT) and PID2022-143279OB-I00 (ACo). Funded by Instituto de Salud Carlos III and European Union NextGenerationEU/PRTR, grant PMP22/00100 (RT and ACo). Funded by AGAUR/Generalitat de Catalunya, grant SGR00490 (RT and ACo). MP has an FPI fellowship, PRE2018-083297, funded by MICIU/AEI/10.13039/501100011033 "ESF Investing in your future".

Presynaptic Dopaminergic Imaging Characterizes Patients with REM Sleep Behavior Disorder Due to Synucleinopathy.

OBJECTIVE: To apply a machine learning analysis to clinical and presynaptic dopaminergic imaging data of patients with rapid eye movement (REM) sleep behavior disorder (RBD) to predict the development of Parkinson disease (PD) and dementia with Lewy bodies (DLB). METHODS: In this multicenter study of the International RBD study group, 173 patients (mean age 70.5 ± 6.3 years, 70.5% males) with polysomnography-confirmed RBD who eventually phenoconverted to overt alpha-synucleinopathy (RBD due to synucleinopathy) were enrolled, and underwent baseline presynaptic dopaminergic imaging and clinical assessment, including motor, cognitive, olfaction, and constipation evaluation. For comparison, 232 RBD non-phenoconvertor patients (67.6 ± 7.1 years, 78.4% males) and 160 controls (68.2 ± 7.2 years, 53.1% males) were enrolled. Imaging and clinical features were analyzed by machine learning to determine predictors of phenoconversion. RESULTS: Machine learning analysis showed that clinical data alone poorly predicted phenoconversion. Presynaptic dopaminergic imaging significantly improved the prediction, especially in combination with clinical data, with 77% sensitivity and 85% specificity in differentiating RBD due to synucleinopathy from non phenoconverted RBD patients, and 85% sensitivity and 86% specificity in discriminating PD-converters from DLB-converters. Quantification of presynaptic dopaminergic imaging showed that an empirical z-score cutoff of -1.0 at the most affected hemisphere putamen characterized RBD due to synucleinopathy patients, while a cutoff of -1.0 at the most affected hemisphere putamen/caudate ratio characterized PD-converters. INTERPRETATION: Clinical data alone poorly predicted phenoconversion in RBD due to synucleinopathy patients. Conversely, presynaptic dopaminergic imaging allows a good prediction of forthcoming phenoconversion diagnosis. This finding may be used in designing future disease-modifying trials. ANN NEUROL 2024;95:1178-1192.

Is REM Sleep Behavior Disorder Changing? Secular Changes Versus Referral Patterns.

Background: Since 2014, there has been increasing public outreach effort regarding isolated/idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD) in Montreal. Objective: To assess if, over time, milder iRBD cases are presenting earlier. Methods: Disease-free survival was compared in two iRBD recruitment epochs: 2004 to 2013 ("earlier") versus 2014to 2022 ("later") and by referral type ("self-referral" vs. "conventional-referral") in three large centers. Results: In Montreal, among 209 subjects followed prospectively, shorter time to phenoconversion was observed in the earlier epoch (5-year phenoconversion = 42% earlier vs. 23% later); diagnosis before 2014 had a 1.8-fold phenoconversion hazard. However, no difference was observed in 248 subjects from Barcelona and 166 from Innsbruck. Analysis of Montreal data found that increased survival in the later epoch was driven by an increasing number of self-referrals, who phenoconverted at 1/3 the rate of physician-referred subjects. Conclusions: Increased patient awareness of iRBD results in earlier presentation to clinical attention, with a longer time to phenoconversion.

Peripheral α-synuclein isoforms are potential biomarkers for diagnosis and prognosis of isolated REM sleep behavior disorder.

INTRODUCTION: Isolated REM sleep behavior disorder (IRBD) represents an early manifestation of the synucleinopathies Parkinson's disease (PD) and dementia with Lewy bodies (DLB). Aggregation of abnormal α-synuclein and its increased expression in the brain is crucial in the development of the synucleinopathies. Whereas α-synuclein gene (SNCA) transcripts are overexpressed in brain, a concomitant reduction occurs in blood of DLB patients. We assessed whether this decrease is also detectable in IRBD. METHODS: 108 IRBD patients and 149 controls were included of which 29 IRBD and 32 control cases were available for expression studies. Expression of SNCAtv1, SNCAtv2, SNCAtv3 and SNCA126 isoforms, and GBA were determined by real-time PCR. Genotype distribution of SNCA SNPs, rs356219 and rs2736990, and correlation with SNCA expression was analyzed. RESULTS: Expression of all SNCA transcripts was reduced in IRBD blood whereas GBA expression did not change. SNCAtv3 expression correlated inversely with IRBD duration, being lower in patients with longer follow-up. Rs356219-AA genotype frequency was increased in IRBD patients who later developed PD and DLB. Rs2736990-CC frequency was increased among IRBD cases who remained disease-free. No correlation was observed between rs356219 and rs2736990 genotypes and SNCA transcript levels. CONCLUSION: SNCA transcript expression is decreased in blood in IRBD, and levels decrease with IRBD duration. Our findings indicate that changes in SNCA expression occur in the earliest stages of the synucleinopathies before motor and cognitive symptoms become apparent.

Former participation in professional football as an occupation in patients with isolated REM sleep behavior disorder leading to a synucleinopathy: a case-control study.

BACKGROUND: Contact sports such as football are associated with late development of neurodegenerative diseases, in part due to the deleterious effect of repetitive head impacts during participation. Isolated REM sleep behavior disorder (IRBD) represents an early manifestation of neurodegenerative diseases including Parkinson disease (RBD) and dementia with Lewy bodies (DLB). We hypothesized that former professional football participation would be overrepresented in IRBD. OBJECTIVE: To assess former participation in professional football as an occupation in IRBD. METHODS: In a case-control retrospective study, having played football as a professional occupation in the Spanish Football Professional Leagues was examined interviewing polysomnographically confirmed IRBD patients and matched controls without IRBD. RESULTS: Among 228 Caucasian Spanish IRBD patients with 68.5 ± 7.2 years, six (2.63%) were retired professional footballers. Length professional football career ranged between 11 and 16 years. Interval between football retirement and IRBD diagnosis was 39.5 ± 6.4 years. At IRBD diagnosis, the six footballers had synucleinopathy biomarkers including pathologic synuclein in the CSF and tissues, nigrostriatal dopaminergic deficit and hyposmia. Follow-up showed that three footballers developed PD and two DLB. None of the controls was a professional footballer. The percentage of professional footballers was higher in IRBD patients than in controls (2.63% versus 0.00%; p = 0.030) and among the general Spanish population (2.63% versus 0.62%; p < 0.0001). CONCLUSION: We found an overrepresentation of former professional footballers in IRBD patients who later developed PD and DLB after four decades from professional retirement. In professional footballers the development of a neurodegenerative disease may be first manifested by IRBD. Screening for IRBD in former footballers might identify individuals with underlying synucleinopathies. Further studies with larger samples are needed to confirm our observations.

Misfolded α-Synuclein Assessment in the Skin and CSF by RT-QuIC in Isolated REM Sleep Behavior Disorder.

BACKGROUND AND OBJECTIVES: Real-time quaking-induced conversion (RT-QuIC) assay detects misfolded α-synuclein (AS) in the skin and CSF of patients with the synucleinopathies Parkinson disease and dementia with Lewy bodies. Isolated REM sleep behavior disorder (IRBD) constitutes the prodromal stage of these synucleinopathies. We aimed to compare the ability of RT-QuIC to identify AS in the skin and CSF of patients with IRBD. METHODS: This was a cross-sectional study where consecutive patients with polysomnographic-confirmed IRBD and age-matched controls without RBD underwent skin biopsy and lumbar puncture the same day. Three-millimeter skin punch biopsies were obtained bilaterally in the cervical region from dorsal C7 and C8 dermatomes and in distal legs. RT-QuIC assessed AS in these 6 skin sites and the CSF. RESULTS: We recruited 91 patients with IRBD and 41 controls. In the skin, sensitivity to detect AS was 76.9% (95% CI 66.9-85.1), specificity 97.6% (95% CI 87.1-99.9) positive predictive value 98.6% (95% CI 91.0-99.8), negative predictive value 65.6% (95% CI 56.6-73.6), and accuracy 83.3% (95% CI 75.9-89.3). In the CSF, the sensitivity was 75.0% (95% CI 64.6-83.6), the specificity was 97.5% (95% CI 86.8-99.9), the positive predictive value was 98.5% (95% CI 90.5-99.8), the negative predictive value was 63.9% (95% CI 55.2-71.9), and the accuracy was 82.0% (95% CI 74.3-88.3). Results in the skin and CSF samples showed 99.2% agreement. Compared with negative patients, RT-QuIC AS-positive patients had a higher likelihood ratio of prodromal Parkinson disease (p < 0.001) and showed more frequently hyposmia (p < 0.001), dopamine transporter imaging single-photon emission CT deficit (p = 0.002), and orthostatic hypotension (p = 0.014). No severe or moderate adverse effects were reported. There was no difference between the percentage of participants reporting mild adverse events secondary to skin biopsy or lumbar puncture (9.1% vs 17.2%; p = 0.053). One hundred and ten (83%) and 104 (80%) participants, respectively, stated they would accept to undergo skin biopsy and lumbar puncture again for research purposes. DISCUSSION: Our study in IRBD shows that (1) RT-QuIC detects AS in the skin and CSF with similar high sensitivity, specificity, and agreement, (2) AS RT-QuIC positivity is associated with supportive features and biomarkers of synucleinopathy, and (3) skin punch biopsy and lumbar puncture have comparable mild adverse effects, tolerance, and acceptance. RT-QuIC in the skin or CSF might represent a patient selection strategy for future neuroprotective trials targeting AS in IRBD. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that RT-QuIC-detected AS in the skin and CSF distinguishes patients with IRBD from controls.

Temporal distribution of sleep onset REM periods and N3 sleep in the MSLT and night polysomnogram of narcolepsy type 1 and other hypersomnias.

INTRODUCTION: The presence of ≥2 sleep onset REM periods (SOREMP) in the Multiple Sleep Latency Test (MSLT) and the previous night polysomnogram (PSG) is part of the diagnostic criteria of narcolepsy, with every SOREMP having the same diagnostic value, despite evidence suggesting that time of SOREMP appearance and their preceding sleep stage might be relevant. We studied the temporal distribution of SOREMPs and associated sleep stages in the MSLT of patients with narcolepsy type 1 (NT1) and other hypersomnias (OH). METHODS: We reviewed consecutive five-nap MSLTs and their preceding PSG from 83 untreated adult patients with hypersomnolence and ≥1 SOREMPs. Wake/N1(W/N1)-SOREMPs, N2-SOREMPs, and N3 sleep presence and time of appearance were analyzed. RESULTS: Thirty-nine patients had NT1 and 44 OH. There were 183 (78%) SOREMPs in patients with NT1 and 83 (31%) in OH. Sixty-seven percent of SOREMPs in NT1 were from W/N1, and 20% -none from wake-in OH (p < 0.001). Most patients (94%) with ≥2 W/N1-SOREMPs had NT1 (specificity 95%, sensitivity 82%). In patients with NT1 but not in OH, W/N1-SOREMPs decreased throughout the day (from 79% in the 1st nap to 33% in the preceding night, p < 0.001), whereas N2-SOREMPs did not change. N3 sleep frequency in the 5th nap was higher in NT1 than in OH (28% vs. 7%, p:0.009). Nocturnal-SOREMP plus ≥4 daytime SOREMPs, Wake-REM transitions, and REM followed by N3 were only seen in NT1. CONCLUSION: Measuring the sleep stage sequence and temporal distribution of SOREMP helps to identify patients with narcolepsy in the MSLT.

Evolution of Clinical-Pathological Correlations in Early-Onset Alzheimer's Disease Over a 25-Year Period in an Academic Brain Bank.

BACKGROUND: Early onset Alzheimer's disease (EOAD) represents a diagnostic challenge and is associated with a high diagnostic delay and misdiagnosis. OBJECTIVE: To describe clinical and pathological data from a pathologically confirmed EOAD cohort and evaluate evolving trends in clinical-pathological correlation accuracy. METHODS: Retrospective review of clinical and neuropathological data of pathologically confirmed EOAD patients (age at onset [AAO] < 60). Comparison between two periods: 1994- 2009 and 2010- 2018. RESULTS: Eighty brain donors were included. Mean AAO, age at death, and diagnostic delay was 55, 66, and 3 years, respectively. Twenty-nine percent had a nonamnestic presentation. Sixteen percent were given a non-AD initial clinical diagnosis (initial misdiagnosis) and 14% received a final misdiagnosis. Nonamnestic presentation patients received more misdiagnoses than amnestic presentation ones (39% versus 7% and 39% versus 3.5%, on initial and final misdiagnosis, respectively). When comparing both time periods, a trend towards a higher diagnostic accuracy in the 2010- 2018 period was observed, mainly on initial misdiagnosis in nonamnestic presentation patients (53% versus 13%, p = 0.069). Diagnostic delay was similar between both periods. Cerebral amyloid angiopathy (96%) and Lewy body co-pathology (55%) were very frequent, while limbic-predominant age-related TDP-43 encephalopathy pathologic changes were only present in 12.5%. CONCLUSION: In the last decade, there has been a trend towards improved diagnostic accuracy in EOAD, which might be explained by improved diagnostic criteria, increasing experience on EOAD and the beginning of the use of biomarkers, although diagnostic delay remains similar. Concomitant neuropathology was very frequent despite the relatively young age of brain donors.

REM sleep latency changes after version 2.1 of the AASM manual for scoring sleep.

BACKGROUND: The classical criteria for scoring REM sleep changed in version 2.1 of the AASM manual for scoring sleep, by allowing N1 epochs with atonia precedent and contiguous to definite REM sleep to be scored as REM sleep in the absence of rapid eye movements when the EEG was compatible. This may shorten the REM latency in the Multiple Sleep Latency Test (MSLT) in naps with wake/N1 to REM transitions, characteristic of narcolepsy type 1. Since REM latency of <5 or <6 min is a biomarker of NT-1 we have assessed the impact of this change in scoring REM sleep in the MSLT. METHODS: Ninety-two consecutive five-nap MSLT studies (460 naps) performed in our center between 2013 and 2019 for evaluation of hypersomnolence with ≥1 sleep onset REM (SOREM) naps were included. REM latencies were measured using both classical and new criteria. RESULTS: SOREMs occurred in 255 (55.9%) naps, 134 directly from wake/N1. By using the new criteria REM latency shortened in 29.1% of these naps (mean 0.2 ± 0.5, range 0-3 min, p < 0.01), predominantly in females. Twenty-eight percent of MSLTs had at least one nap with a shortened REM latency (mean 0.1 min ± 0.2, p < 0.01). Only two MSLTs changed their REM latency to <5 min and none to <6 min with the new rules. CONCLUSIONS: The criterion to define REM sleep onset significantly influences its latency and should be considered when comparing studies performed before or after version 2.1 modification. The clinical relevance of this scoring change is probably minimal.

Assessment of Cognitive Symptoms in Brain Bank-Registered Control Subjects: Feasibility and Utility of a Telephone-Based Screening.

BACKGROUND: For neuroscience research, the study of brain tissue of neurologically unimpaired subjects is crucial to interpret findings in neurodegenerative diseases. Sub-optimal neurological follow-up and the presence of neuropathological lesions in supposedly asymptomatic subjects casts doubt as to whether these subjects present an undetected underlying neurodegenerative disease or are resilient to neurodegeneration. OBJECTIVE: We aimed to assess whether the control donors registered in the Neurological Tissue Bank-Hospital Clínic-IDIBAPS (NTB-HCI) are still free of cognitive symptoms at follow-up and to evaluate the feasibility and utility of a telephone-based screening. METHODS: All control subjects older than 65 years registered at the NTB-HCI database were selected for the study. After a structured telephone interview, those subjects already diagnosed with a neurological disease were excluded. Then, a cognitive screening was performed, including the telephone version of the Mini-Mental State Examination (t-MMSE) and the eight-item interview (AD-8) to the subject and to one informant (AD-8i). RESULTS: In total, 73.8% of the registered donors collaborated in the study. Only 21.4% had at least one of the three cognitive screening tools impaired, and 2.7% had a profile highly suggestive of cognitive impairment. AD-8i correlated moderately with t-MMSE. CONCLUSION: Telephone-based neurologic screening in control donors is feasible and was within the normal range in most of the subjects in our cohort. Albeit, the involvement of neurologists and periodic neurological screenings are desirable in a control subjects brain donor program, AD8-i could be used to screen the control's neurological status in the absence of accurate clinical data at the time of the death.

Characterization of sleep in six patients with pantothenate kinase-associated neurodegeneration.

BACKGROUND: Pantothenate kinase-associated neurodegeneration (PKAN) is a rare neurologic disorder included in the group of neurodegeneration with brain iron accumulation diseases (NBIA). Information regarding sleep in patients with PKAN is limited. OBJECTIVES: To describe the clinical and polysomnographic characteristics of sleep in six patients with genetically confirmed PKAN. METHODS: The evaluation included a clinical interview, sleep questionnaires -Epworth Sleepiness Scale (ESS), Pittsburgh Sleep Quality Index (PSQI) and Hospital Anxiety and Depression Scale (HADS)- and a video-polysomnography (VPSG). In addition to standard sleep measures we manually quantified sleep spindle density in stage N2 and rapid eye movements in REM sleep comparing the results with matched controls. Quantification of EMG activity in REM sleep was performed following standard criteria. RESULTS: All the patients reported at least one sleep complaint, most commonly sleep fragmentation (4/6) and sleep onset insomnia (3/6). ESS and PSQI were abnormal in 3/6 and 4/6, respectively. VPSG showed in 4/6 decreased ocular movements during REM sleep, an increase in sleep spindles in 3/6 (all of them with deep brain pallidal stimulation), an absence of slow wave sleep in 2 and undifferentiated NREM sleep and delayed sleep phase in one. Three patients had an abnormal sleep apnea/hypopnea index, and 2 periodic limb movements of sleep. REM sleep muscular atonia was preserved in all. CONCLUSIONS: Sleep disorders are common in patients with PKAN. Although our sample is small and heterogeneous, with different symptomatic treatments possibly influencing the results, it suggests that evaluation of sleep should be considered in their management.

Stridor during sleep: description of 81 consecutive cases diagnosed in a tertiary sleep disorders center.

STUDY OBJECTIVES: To describe the characteristics of stridor during sleep (SDS) in a series of adults identified by video-polysomnography (V-PSG). METHODS: Retrospective clinical, V-PSG, laryngoscopic, and therapeutic data of patients diagnosed with SDS in a tertiary referral sleep disorders center between 1997 and 2017. RESULTS: A total of 81 patients were identified (56.8% males, age 61.8 ± 11.2 years). Related etiologies were multiple system atrophy (MSA), amyotrophic lateral sclerosis, spinocerebellar ataxia type 1, anti-IgLON5 disease, fatal familial insomnia, brainstem structural lesions, vagus nerve stimulation, recurrent laryngeal nerve injury, the effect of radiotherapy on the vocal cords, cervical osteophytes, and others. Stridor during wakefulness coexisted in 13 (16%) patients and in MSA was only seen in the parkinsonian form. Laryngoscopy during wakefulness in 72 (88.9%) subjects documented vocal cord abductor impairment in 65 (90.3%) and extrinsic lesions narrowing the glottis in 2 (2.4%). The mean apnea-hypopnea index (AHI) was 21.4 ± 18.6 and CT90 was 11.5 ± 19.1. Obstructive AHI > 10 occurred in 52 (64.2%) patients and central apnea index >10 in 2 (2.4%). CPAP abolished SDS, obstructive apneic events and oxyhemoglobin desaturations in 58 of 60 (96.7%) titrated patients with optimal pressure of 9.0 ± 2.3 cm H20. Tracheostomy in 19 (23.4%) and cordotomy in 3 (3.7%) subjects also eliminated SDS. CONCLUSIONS: SDS in adults is linked to conditions that damage the brainstem, recurrent laryngeal nerve, and vocal cords. V-PSG frequently detects obstructive sleep apnea and laryngoscopy usually shows vocal cord abductor dysfunction. CPAP, tracheostomy, and laryngeal surgery abolish SDS.