Increased Accuracy, Confidence, and Efficiency in Anterior Ethmoidal Artery Identification with Segmented Image Guidance.

OBJECTIVE: To determine whether using image guidance technology with 3-dimensional image segmentation increases the endoscopic surgeon's accuracy, efficiency, and confidence in identifying the anterior ethmoidal artery. METHODS: This is a cross-sectional study of attending physicians and residents at an academic medical center. Because identification of the anterior ethmoidal artery during image-guided surgery can be challenging, we studied the effect of anterior ethmoidal artery image segmentation (ie, partitioning and coloring) on surgeon test performance. A computerized test was administered to 16 surgeons who were asked to identify the anterior ethmoidal artery on multiplanar computed tomographic images and to answer multiple-choice questions. Half the questions showed segmented images of the anterior ethmoidal artery, and half showed images without segmentation. Efficiency and accuracy of identification and subjective surgeon confidence were determined for each question. Descriptive statistics were used to compare test performance for identification of the anterior ethmoidal artery on images with or without segmentation. RESULTS: Percentage of correct answers ( P < .001), efficiency ( P < .001), and confidence ( P < .001) in identification of the anterior ethmoidal artery were significantly better with segmented computed tomographic images. DISCUSSION: We demonstrated that use of segmented images improves surgeons' accuracy, confidence, and efficiency for identification of the anterior ethmoidal artery. IMPLICATIONS FOR PRACTICE: We describe how segmentation can allow surgeons to improve the surgical course by increasing their accuracy, confidence, and efficiency in identifying the anterior ethmoidal artery.

Virtual Mapping of the Frontal Recess: Guiding Safe and Efficient Frontal Sinus Surgery.

Objective To define relationships between the frontal sinus opening, ostia of other frontal recess cells, and endoscopic landmarks and to develop a clinically useful framework to guide frontal sinus surgery. Study Design Retrospective review. Setting Tertiary care academic referral center. Methods Adult patients with computed tomography (CT) without sinonasal pathology were included. Virtual endoscopy (using OsiriX) and corresponding CT reconstructions were used to identify all visible ostia in the frontal recess and characterize their positions in spaces between the uncinate/agger nasi (U), bulla ethmoidalis (EB), and middle turbinate (MT). Results Two hundred sides in 100 patients (median age 51 years, 62% female) were analyzed. The "center" of each map was defined as the intersection of spaces between U, EB, and MT. The frontal sinus opening was in the "center" in 53% of frontal recesses, lateral to this position in 29%, and anterior in 11%. When the frontal sinus opening was at the "center," anterior ostia drained frontal Kuhn T cells in 51% and intersinus septal cells in 23%. The skull base attachment of the apical strut of the uncinate process demarcated medial and lateral within the space between U and EB, with the opening to the frontal sinus medial in 68% and lateral in 31%. Left-right asymmetry in frontal sinus openings was noted in 46% of patients. Conclusion Combining preoperative imaging and knowledge of these anatomic relationships may facilitate more efficient frontal outflow tract identification and instrumentation. This represents the first and largest description of ostial configurations relative to endoscopic structural landmarks. LEVEL OF EVIDENCE: 4.

The Emerging Role of 3-Dimensional Printing in Rhinology.

Nasal septal perforations, particularly those that are large and irregular in shape, often present as challenging surgical dilemmas. New technology has allowed us to develop techniques using computed tomography imaging and 3-dimensional (3D) printers to design custom polymeric silicone septal buttons. These buttons offer patients an option that avoids a surgical intervention when standard buttons do not fit well or are not tolerated. Preliminary data suggest that buttons designed by 3D printer technology provide more comfort than standard commercially available or hand-carved buttons with equivalent reduction of symptoms.

Three-dimensional printing of large nasal septal perforations for optimal prosthetic closure.

BACKGROUND: Since 1972, patients with large nasal perforations, who were symptomatic, and who were not candidates for surgery, had the option of custom prosthetic closure at Mayo Clinic. Although septal prostheses have helped many patients, 27% of pre-1982 patients chose not to keep the prosthesis in place. Two-dimensional computed tomography (CT) sizing resulted in more of the patients choosing to retain the prosthesis. The introduction of three-dimensional (3-D) printing to the sizing process offered the potential of further improved retention by refinement in prosthesis fit. OBJECTIVE: To describe the fabrication of nasal septal prostheses by using 3-D printing for sizing and to compare the retention rate of 3-D-sized prostheses with those that used previous sizing methods. METHODS: Twenty-one consecutive patients who had placement of septal prostheses sized by using 3-D printed templates were studied. CT image data were used to print 3-D templates of the exact shape of the patient's septal perforation, and medical-grade silastic prostheses were fabricated to fit. In four cases, the 3-D printed template allowed preoperative surgical simulation. Metrics collected included prosthesis retention; symptoms, including intranasal crusting and epistaxis; and previous prosthetic closure failures. RESULTS: Twenty of the twenty-one patients had improvement in symptoms. The mean diameter of the perforations was 2.4 cm; the mean closure time by the end of the study period was 2.2 years. All but two patients chose to keep their prosthesis in place, for a retention rate of 90%. Seven patients with successful closure had failed previously with prior prosthesis sized without the current 3-D printing methodology. This 90% retention rate exceeded the previous rates before the introduction of 3-D sizing. CONCLUSION: Sizing done by 3-D printing for prosthetic closure of nasal septal perforations resulted in a higher retention rate in helping patients with these most-challenging nasal septal perforations.

The effect of vibrissae on subjective and objective measures of nasal obstruction.

BACKGROUND: Nasal congestion and/or obstruction represents a prevalent and extensively studied problem. No published research exists that describes the impact of nasal hair (vibrissae) on nasal obstruction. OBJECTIVE: To assess the impact of nasal vibrissae on subjective and objective measurements of nasal obstruction. METHODS: In this prospective study, 30 healthy participants without nasal symptoms were assessed for baseline vibrissae density and were treated with a topical decongestant. The subjects were then asked to subjectively assess nasal breathing by using four questions from the Nasal Obstruction Symptom Evaluation instrument before undergoing rhinomanometry. Nasal vibrissae were then trimmed, and the participants repeated the subjective and objective assessments. Pre- and postintervention outcomes, including symptom scores, nasal airflow, and resistance, were compared by using statistical analysis. RESULTS: Statistically significant improvement was noted in subjects' nasal airway specific symptom scores and in objective measurements of their nasal airway. Patients with moderate or many vibrissae at baseline were noted to have greater likelihood of improvement in subjective and objective obstruction assessments than patients rated with few. CONCLUSION: In these 30 subjects, statistically significant improvement occurred in both subjective and objective assessments of nasal obstruction, particularly in patients with greater density of vibrissae. These findings support further study of the potential benefit of the reduction of vibrissae density in some patients with nasal obstruction.

Volumetric computed tomography analysis of the olfactory cleft in patients with chronic rhinosinusitis.

BACKGROUND: Commonly used computed tomography (CT) staging systems for chronic rhinosinusitis (CRS) focus on the sinuses and do not quantify disease in the olfactory cleft. The goal of the current study was to determine whether precise measurements of olfactory cleft opacification better correlate with olfaction in patients with CRS. METHODS: Olfaction was assessed using the 40-item Smell Identification Test (SIT-40) before and after sinus surgery in adult patients. Olfactory cleft opacification was quantified precisely using three-dimensional (3D), computerized volumetric analysis, as well as via semiquantitative Likert scale estimations at predetermined anatomic sites. Sinus opacification was also quantified using the Lund-Mackay staging system. RESULTS: The overall cohort (n = 199) included 89 (44.7%) patients with CRS with nasal polyposis (CRSwNP) and 110 (55.3%) with CRS without nasal polyposis (CRSsNP). The olfactory cleft opacified volume correlated with objective olfaction as determined by the SIT-40 (Spearman's rank correlation coefficient [Rs ] = -0.461; p < 0.001). The correlation was significantly stronger in the CRSwNP subgroup (Rs = -0.573; p < 0.001), whereas no appreciable correlation was found in the CRSsNP group (Rs = -0.141; p = 0.141). Correlations between sinus-specific Lund-Mackay CT scoring and SIT-40 scores were weaker in the CRSwNP (Rs = -0.377; p < 0.001) subgroup but stronger in the CRSsNP (Rs = -0.225; p = 0.018) group when compared to olfactory cleft correlations. Greater intraclass correlations (ICCs) were found between quantitative volumetric measures of olfactory cleft opacification (ICC = 0.844; p < 0.001) as compared with semiquantitative Likert grading (ICC = 0.627; p < 0.001). CONCLUSION: Quantitative measures of olfactory cleft opacification correlate with objective olfaction, with the strongest correlations seen in patients with nasal polyps.

Identifying the presence of clinically significant hepatic involvement in hereditary haemorrhagic telangiectasia using a simple clinical scoring index.

BACKGROUND & AIMS: Though hepatic involvement is common in patients with hereditary haemorrhagic telangiectasia (HHT), symptomatic liver disease is rare but potentially fatal without liver transplantation. Factors associated with clinically significant liver disease in patients with HHT are unknown. METHODS: In this prospective cohort study, we included consecutive patients from 2001 to 2011 with definite HHT, who underwent systematic protocol screening including contrast-enhanced hepatic CT and/or abdominal ultrasound. Using a multivariable logistic regression model, we developed a simple clinical scoring index to identify the presence of symptomatic liver disease (cardiac failure, portal hypertension, or biliary disease) or 'at-risk' liver disease (asymptomatic patients, with hepatic bruit, abnormal liver biochemistry, or elevated cardiac index). RESULTS: Of 316 patients with definite HHT, 171 patients (54.1%; age 53.4 ± 15.2 y, 101 females) had hepatic involvement on imaging. Twenty-nine patients had symptomatic liver disease (22 patients with high-output heart failure); 45 patients were 'at-risk' for liver disease. Using multivariable logistic regression analysis, we derived a score using age, gender, hemoglobin and alkaline phosphatase at presentation which could accurately distinguish patients with clinically significant liver involvement from patients with no or incidental liver lesions (c-statistic=0.80). A score <3 indicated low risk (<5%) and score >6 indicated high risk (>80%) of harboring clinically significant liver disease in HHT. CONCLUSIONS: A simple scoring system can distinguish patients at low, moderate, and high risk of harboring clinically significant liver disease. With validation, this score may be used to identify patients for individualized screening and enrollment in clinical trials.

Computed tomography scans as an objective measure of disease severity in chronic rhinosinusitis.

OBJECTIVES: A truly objective method of measuring disease severity in chronic rhinosinusitis (CRS) has only recently existed. We evaluated computed tomography (CT) scans of CRS patients using this novel objective 3D computerized system and compared results with a novel 2D computerized analysis of a single coronal slice through the osteomeatal complex (OMC) and subjective methods including Lund-Mackay and Zinreich's modified Lund-Mackay. STUDY DESIGN: Prospective multicenter study. SETTING: Two academic tertiary referral centers. SUBJECTS AND METHODS: Forty-six adults with a diagnosis of CRS underwent CT examination and received an intramuscular triamcinolone injection, dosage weight dependent, followed by CT scan 4 to 5 weeks later. Recruitment lasted 21 months. Scans were evaluated with all 4 scoring methods over 5 months. RESULTS: The Lin's concordance class correlation (CCC) of the OMC method revealed the best correlation to the 3D volumetric computerized values (0.915), followed by the Zinreich (0.904) and Lund-Mackay methods (0.824). Posttreatment results demonstrated that both the OMC (0.824) and Zinreich's (0.778) methods had strong agreement with the 3D volumetric methods and were very sensitive to change, whereas the Lund-Mackay (0.545) had only moderate agreement. CONCLUSION: Computerized CT analysis provides the most comprehensive, objective, and reproducible method of measuring disease severity and is very sensitive to change induced by treatment intervention. A 2D coronal image through the OMC provides a valid, user-friendly method of assessing CRS and is representative of CRS severity in all sinuses. Zinreich's subjective method correlated well overall, but the Lund-Mackay method lagged behind in disease representation and sensitivity to change.

Three-dimensional volumetric computed tomographic scoring as an objective outcome measure for chronic rhinosinusitis: clinical correlations and comparison to Lund-Mackay scoring.

BACKGROUND: We aimed to test the hypothesis that three-dimensional (3D) volume-based scoring of computed tomography (CT) images of the paranasal sinuses was superior to Lund-Mackay CT scoring of disease severity in chronic rhinosinusitis (CRS). We determined correlation between changes in CT scores (using each scoring system) with changes in other measures of disease severity (symptoms, endoscopic scoring, and quality of life) in patients with CRS treated with triamcinolone. METHODS: The study group comprised 48 adult subjects with CRS. Baseline symptoms and quality of life were assessed. Endoscopy and CT scans were performed. Patients received a single systemic dose of intramuscular triamcinolone and were reevaluated 1 month later. Strengths of the correlations between changes in CT scores and changes in CRS signs and symptoms and quality of life were determined. RESULTS: We observed some variability in degree of improvement for the different symptom, endoscopic, and quality-of-life parameters after treatment. Improvement of parameters was significantly correlated with improvement in CT disease score using both CT scoring methods. However, volumetric CT scoring had greater correlation with these parameters than Lund-Mackay scoring. CONCLUSION: Volumetric scoring exhibited higher degree of correlation than Lund-Mackay scoring when comparing improvement in CT score with improvement in score for symptoms, endoscopic exam, and quality of life in this group of patients who received beneficial medical treatment for CRS.

Mapping the frontal sinus ostia using virtual endoscopy.

OBJECTIVES/HYPOTHESIS: To determine the relative location of the frontal sinus opening to other frontal cells using virtual endoscopy; and to assess whether the relative location of the frontal sinus ostium can be predicted. STUDY DESIGN: Retrospective analysis of high-resolution computed tomography scans from 50 adult patients without frontal sinus disease or previous sinus surgery. METHODS: Using virtual endoscopy software, 100 frontal recesses were mapped for the presence and relative position of the frontal sinus ostium to the following cells: agger nasi (ANC); frontal bullar; frontal types 1, 2, and 3; supraorbital ethmoid; suprabullar; and intersinus septal cells. RESULTS: ANC and frontal type 3 cells were present in 92% and 45% of frontal recesses, respectively. All other cell types had a prevalence of ≤ 25%. Fifty percent of recesses had two rows of ostia anterior to posterior (AP), and the frontal opening was anterior in 52%. When there were three rows of cells AP (39%), the frontal opening was in the center in 64% of cases. Thirty-five percent of recesses had two rows of ostia medial to lateral (ML), and the frontal opening was medial 80% of the time. When there were three rows of openings ML (45%), the frontal opening was in the center 56% of the time. CONCLUSIONS: The frontal sinus recess is variable and complex. Virtual endoscopy can be used to analyze the frontal recess and assist in presurgical planning. Although there is variability in the ostial configuration present in the frontal recess, the probable position of the frontal sinus ostium can be predicted.

Surgical modifications of the upper airway for obstructive sleep apnea in adults: a systematic review and meta-analysis.

A substantial portion of patients with obstructive sleep apnea (OSA) seek alternatives to positive airway pressure (PAP), the usual first-line treatment for the disorder. One option is upper airway surgery. As an adjunct to the American Academy of Sleep Medicine (AASM) Standards of Practice paper, we conducted a systematic review and meta-analysis of literature reporting outcomes following various upper airway surgeries for the treatment of OSA in adults, including maxillomandibular advancement (MMA), pharyngeal surgeries such as uvulopharyngopalatoplasty (UPPP), laser assisted uvulopalatoplasty (LAUP), and radiofrequency ablation (RFA), as well as multi-level and multi-phased procedures. We found that the published literature is comprised primarily of case series, with few controlled trials and varying approaches to pre-operative evaluation and post-operative follow-up. We include surgical morbidity and adverse events where reported but these were not systematically analyzed. Utilizing the ratio of means method, we used the change in the apnea-hypopnea index (AHI) as the primary measure of efficacy. Substantial and consistent reductions in the AHI were observed following MMA; adverse events were uncommonly reported. Outcomes following pharyngeal surgeries were less consistent; adverse events were reported more commonly. Papers describing positive outcomes associated with newer pharyngeal techniques and multi-level procedures performed in small samples of patients appear promising. Further research is needed to better clarify patient selection, as well as efficacy and safety of upper airway surgery in those with OSA.

Gene transcription changes in asthmatic chronic rhinosinusitis with nasal polyps and comparison to those in atopic dermatitis.

BACKGROUND: Asthmatic chronic rhinosinusitis with nasal polyps (aCRSwNP) is a common disruptive eosinophilic disease without effective medical treatment. Therefore, we sought to identify gene expression changes, particularly those occurring early, in aCRSwNP. To highlight expression changes associated with eosinophilic epithelial inflammation, we further compared the changes in aCRSwNP with those in a second eosinophilic epithelial disease, atopic dermatitis (AD), which is also closely related to asthma. METHODS/PRINCIPAL FINDINGS: Genome-wide mRNA levels measured by exon array in both nasosinus inflamed mucosa and adjacent polyp from 11 aCRSwNP patients were compared to those in nasosinus tissue from 17 normal or rhinitis subjects without polyps. Differential expression of selected genes was confirmed by qRT-PCR or immunoassay, and transcription changes common to AD were identified. Comparison of aCRSwNP inflamed mucosa and polyp to normal/rhinitis tissue identified 447 differentially transcribed genes at > or = 2 fold-change and adjusted p-value < 0.05. These included increased transcription of chemokines localized to chromosome 17q11.2 (CCL13, CCL2, CCL8, and CCL11) that favor eosinophil and monocyte chemotaxis and chemokines (CCL18, CCL22, and CXCL13) that alternatively-activated monocyte-derived cells have been shown to produce. Additional transcription changes likely associated with Th2-like eosinophilic inflammation were prominent and included increased IL1RL1 (IL33 receptor) and EMR1&3 and decreased CRISP2&3. A down-regulated PDGFB-centric network involving several smooth muscle-associated genes was also implicated. Genes at 17q11.2, genes associated with alternative activation or smooth muscle, and the IL1RL1 gene were also differentially transcribed in AD. CONCLUSIONS/SIGNIFICANCE: Our data implicate several genes or gene sets in aCRSwNP and eosinophilic epithelial inflammation, some that likely act in the earlier stages of inflammation. The identified gene expression changes provide additional diagnostic and therapeutic targets for aCRSwNP and other eosinophilic epithelial diseases.

Dose and image quality evaluation of a dedicated cone-beam CT system for high-contrast neurologic applications.

OBJECTIVE: The purpose of our study was to evaluate the dose and image quality performance of a dedicated cone-beam CT (CBCT) scanner in comparison with an MDCT scanner. MATERIALS AND METHODS: The conventional dose metric, CT dose index (CTDI), is no longer applicable to CBCT scanners. We propose to use two dose metrics, the volume average dose and the mid plane average dose, to quantify the dose performance in a circular cone-beam scan. Under the condition of equal mid plane average dose, we evaluated the image quality of a CBCT scanner and an MDCT scanner, including high-contrast spatial resolution, low-contrast spatial resolution, noise level, CT number uniformity, and CT number accuracy. RESULTS: For the sinus scanning protocol, the CBCT system had comparable high-contrast resolution and inferior low-contrast resolution to those obtained with the MDCT scanner when the doses were matched (mid plane average dose 9.2 mGy). The CT number uniformity and accuracy were worse on the CBCT scanner. The image artifacts caused by beam hardening and scattering were also much more severe on the CBCT system. CONCLUSION: With a matched radiation dose, the CBCT system for sinus study has comparable high-contrast resolution and inferior low-contrast resolution relative to the MDCT scanner. Because of the more severe image artifacts on the CBCT system due to the small field of view and the lack of accurate scatter and beam-hardening correction, the utility of the CBCT system for diagnostic tasks related to soft tissue should be carefully assessed.

Three-dimensional CT reconstruction and virtual endoscopic study of the ostial orientations of the frontal recess.

BACKGROUND: Safe and efficient endoscopic frontal sinus surgery requires a thorough knowledge of the location of the frontal sinus outflow tract. This study was designed to describe the prevalence of the different frontal recess cells and 3D analysis by virtual endoscopy of their ostial orientation in relation to the frontal ostium. METHODS: Fifty high-resolution CT scans (100 sides) of disease-free paranasal sinuses were reviewed using triplanar and virtual 3D analysis. The prevalence and ostial locations of the frontal recess cells and the relationship of the various ostia to the frontal sinus ostium were mapped and analyzed. RESULTS: The cell type, prevalence, and most common relationship of the cell's ostium to the frontal ostium were intersinus septal cells, 7% medial and anterior; Kuhn type 1 cells, 28%, lateral and anterior; Kuhn type 2 cells, 6%, anterior and lateral; Kuhn type 3 cells, 11%, medial or lateral; supraorbital ethmoid cells, 11%, posterior; suprabullar cells, 68%, posterior; and frontal bullar cells, 16%, posterior or lateral. In 35% of the sides, none of the aforementioned cell types were found. There were many blind recesses that were seen in all locations except anterolateral to the frontal ostium. Openings of adjacent pneumatized middle turbinates were often posteromedial to the frontal ostium. Agger nasi cells were present in at least 86%, opening lateral to frontal ostium. CONCLUSION: Frontal outflow tract mapping by virtual endoscopy and knowledge of the ostial configurations will help surgeons perform more efficient and accurate surgery particularly for minimally invasive approaches including balloon dilation.

Uvulopalatopharyngoplasty in the management of obstructive sleep apnea: the mayo clinic experience.

OBJECTIVE: To assess the role of uvulopalatopharyngoplasty (UPPP) in the treatment of obstructive sleep apnea (OSA) using polysomnography (PSG) data within 6 months before and after surgery. PATIENTS AND METHODS: We analyzed PSG and body mass index (BMI) data from patients with OSA who were 18 years or older and who underwent UPPP between January 1, 1988, and August 31, 2006. RESULTS: Sixty-three patients (51 men [81.0%]; mean +/- SD age, 42.1+/-13.9 years; mean +/- SD BMI, 34.9+/-7.2) underwent PSG a mean +/- SD of 50+/-47 days before and 88.5+/-34.0 days after UPPP. Surgical cure was defined as a postoperative apnea-hypopnea index (AHI) of 5 or less. Fifteen patients (24%) achieved a surgical cure. Twenty-one patients (33%) had a postoperative AHI of 10 or less, whereas 32 (51%) achieved a 50% or greater reduction in AHI and/or an AHI of 20 or less. No significant changes were noted in BMI before and 6 months after UPPP. Patients who attained an AHI of 5 or less were younger (mean +/- SD age, 35.9+/-13.1 vs 44+/-13.7 years; P=.05), had lower BMIs (mean +/- SD, 30.8+/-6.5 vs 34.6+/-6.6; P=.05), and had less severe OSA (mean +/- SD AHI, 38.1+/-33.6 vs 69.6+/-32.8; P=.004). Of the 48 patients (76%) with a post-UPPP AHI greater than 5, 35 (56%) received continuous positive airway pressure, with a mean reduction in pressure of 1.4 cm H(2)O (95% confidence interval, -0.4 to -2.4 cm H(2)O). CONCLUSION: Independent of changes in BMI, in our retrospective analysis, UPPP achieved an AHI of 5 or less in 24% and an AHI of 10 or less in 33% of patients with OSA who underwent PSG 6 months before and after surgery. In those with residual OSA who received continuous positive airway pressure, the required pressure setting decreased by 1.4 cm H(2)O.

Rhabdomyolysis after transnasal repair of anterior basal encephalocele.

BACKGROUND: Postoperative Rhabdomyolysis (RM) is rare after neurosurgical procedures. Furthermore, it has not been observed after transnasal approaches. The authors report a case of idiopathic RM occurring after transnasal resection of a sincipital encephalocele. CASE DESCRIPTION: A 32-year-old woman underwent a transnasal resection of a sincipital encephalocele after 6 years of intermittent clear nasal drainage. Postoperatively, she experienced severe back pain, peripheral neuropathy, associated with a markedly elevated creatinine kinase, and severe RM. The patient was treated with hydration and forced urine alkalization and treated symptomatically for her pain and neuropathy. She ultimately made a full recovery without complication. CONCLUSION: Rhabdomyolysis is a rare but known complication of neurosurgical procedures. We report the first known case report of RM after a transnasal procedure. Furthermore, a review of documented postneurosurgical cases of RM is presented and reveals that the causes and risk factors for this complication after neurosurgery are similar to those in other surgical subspecialties.

Effects of continuous positive airway pressure on stridor in multiple system atrophy-sleep laryngoscopy.

The presence of stridor in patients with multiple system atrophy (MSA) is associated with poor prognosis, mainly due to a high risk of complete airway obstruction at night. Continuous positive airway pressure (CPAP) therapy has been proposed as a treatment of MSA-associated stridor, but, until now, there has been no visual documentation of the effect of CPAP on laryngeal patency during nonpharmacologically induced spontaneous sleep of a patient with MSA. We present a video-laryngoscopic documentation of a 57-year-old woman with MSA who was evaluated for nocturnal stridor. Direct laryngoscopy during sleep without pharmacologic sedation documented inspiratory adduction of the vocal cords with downward displacement of the larynx. Application of CPAP resulted in improvement of stridor, distension of the hypopharynx, abduction of vocal cords, and reduction of the downward displacement of the larynx. We discuss the possible mechanisms of action of CPAP in MSA-associated stridor.