Dr. Liu joined the Stanford University School of Medicine faculty as an Assistant Professor of Otolaryngology in 2014. He currently serves as co-director of the Stanford Sleep Surgery Fellowship Program. He practices the full scope of sleep apnea surgery.

Dr. Liu boarded at The Lawrenceville School before attending Stanford as an undergrad. He received his medical and dental degrees from the University of California-San Francisco (UCSF). He was also a former Howard Hughes Medical Institute (HHMI) Research Scholar (Cloister Program). After maxillofacial surgery residency at UCSF, Dr. Liu completed his sleep surgery fellowship at Stanford.

In addition to the full scope of sleep apnea surgery (nasal, palatal, hypoglossal nerve stimulation, genioglossus advancement, distraction osteogenesis maxillary expansion, maxillomandibular advancement), Dr. Liu has expertise in orthognathic surgery (particularly surgery-first orthognathic surgery), and repair of complex primary and secondary facial trauma.In that capacity, he also serves as a preceptor for the Stanford Oculoplastic Surgery Fellowship.

Dr. Liu lectures extensively in the U.S. and internationally on sleep apnea surgery. His active areas of research include dynamic airway examination in OSA, virtual surgical planning for precision facial skeletal surgery, and neuromodulation of the head and neck. He has published over 40 scientific articles and medical texts on OSA, with original scientific work on MMA, maxillary expansion, and hypoglossal nerve stimulation.

Clinical Focus

  • Sleep Apnea, Obstructive
  • Sleep Apnea Surgery
  • Maxillomandibular Advancement (MMA)
  • Hypoglossal Nerve Stimulation (Inspire)
  • Orthognathic Surgery
  • Facial Deformity
  • Facial Bone Contouring
  • Facial Trauma
  • Oral and Maxillofacial Surgery

Academic Appointments

  • Assistant Professor - Med Center Line, Otolaryngology - Head & Neck Surgery Divisions

Administrative Appointments

  • Co-Director, Sleep Surgery Fellowship (2015 - Present)
  • Preceptor, Oculoplastic Surgery Fellowship (2016 - Present)

Honors & Awards

  • Scholar, Howard Hughes Medical Institute (2005-06)

Boards, Advisory Committees, Professional Organizations

  • Member, Sleep Disorders Committee, American Academy of Otolaryngology-Head and Neck Surgery (2016 - Present)

Professional Education

  • Fellowship, Stanford University, Sleep Surgery (2014)
  • Residency, University of California - San Francisco (UCSF), Oral and Maxillofacial Surgery (2013)
  • MD, University of California - San Francisco (UCSF), Medicine (2011)
  • DDS, University of California - San Francisco (UCSF), Dentistry (2007)
  • BS, Stanford University, Biology (2000)

Research & Scholarship

Clinical Trials

  • SPG Neurostimulation in Cluster Patients Recruiting

    Hypothesis: Stimulation of the SPG at low frequencies (20 Hz)is believed to cause a physiological parasympathetic upregulation which increases mean velocity in middle cerebral artery (VMCA) and diameter of the superficial temporal artery.

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2016-17 Courses


All Publications

  • Continuing the Original Stanford Sleep Surgery Protocol From Upper Airway Reconstruction to Upper Airway Stimulation: Our First Successful Case. Journal of oral and maxillofacial surgery : official journal of the American Association of Oral and Maxillofacial Surgeons Liu, S. Y., Riley, R. W. 2017


    In 1993, a surgical protocol for dynamic upper airway reconstruction in patients with obstructive sleep apnea (OSA) was published, and it became commonly known as the Stanford phase 1 and 2 sleep surgery protocol. It served as a platform on which research and clinical studies have continued to perfect the surgical care of patients with OSA. However, relapse is inevitable in a chronic condition such as OSA, and a subset of previously cured surgical patients return with complaints of excessive daytime sleepiness. This report describes a patient who was successfully treated with phase 1 and 2 operations more than a decade previously. He returned at 65 years of age with relapse of moderate OSA, and after workup with polysomnography and drug-induced sleep endoscopy, he underwent upper airway stimulation of the hypoglossal nerve that resulted in cure of OSA. This case shows why upper airway stimulation is an appropriate option for patients with OSA and previously successful maxillomandibular advancement.

    View details for DOI 10.1016/j.joms.2017.02.008

    View details for PubMedID 28294946

  • An Accurate Method of Designing and Performing Individual-Specific Genioglossus Advancement. Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery Liu, S. Y., Huon, L. K., Zaghi, S., Riley, R., Torre, C. 2017; 156 (1): 194–97


    There is too much individual patient variation in mandibular anatomy for any single described genioglossus advancement technique to be used consistently. Virtual surgical planning allows surgeons to design genioglossus osteotomy that captures the structures of interest. Intraoperative osteotomy and positioning guides mitigate known risks of the procedure while maximizing the reproducibility and efficacy of the procedure. In this report, we demonstrate the protocol step by step as it had been used on 10 patients, and we highlight 3 clinical scenarios that exemplify its utility.

    View details for DOI 10.1177/0194599816670366

    View details for PubMedID 28045634

  • Efficacy of Maxillomandibular Advancement Examined with Drug-Induced Sleep Endoscopy and Computational Fluid Dynamics Airflow Modeling. Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery Liu, S. Y., Huon, L., Iwasaki, T., Yoon, A., Riley, R., Powell, N., Torre, C., Capasso, R. 2016; 154 (1): 189-195


    To use drug-induced sedation endoscopy (DISE) and computational fluid dynamics (CFD) modeling to study dynamic airway and airflow changes after maxillomandibular advancement (MMA), and how the changes correlate with surgical success based on polysomnography parameters.Retrospective cohort study.University medical center.DISE was rated with the VOTE (velum, oropharynx, tongue, epiglottis) classification, and CFD was used to model airflow velocity and negative pressure exerted on pharyngeal wall. Changes in VOTE score by site and CFD measurements were correlated with perioperative polysomnography outcomes of apnea-hypopnea index (AHI), apnea index (AI), oxygenation desaturation index (ODI), and lowest oxygen saturation.After MMA, 20 subjects (17 males, 3 females) with a mean age of 44 ± 12 years and body mass index of 27.4 ± 4.6 kg/m(2) showed mean decreases in AHI (53.6 ± 26.6 to 9.5 ± 7.4 events/h) and ODI (38.7 ± 30.3 to 8.1 ± 9.2 events/h; P < .001). Improvement in lateral pharyngeal wall collapse during DISE based on VOTE score correlated with the most decrease in AHI (60.0 ± 25.6 to 7.5 ± 3.4 events/h) and ODI (46.7 ± 29.8 to 5.3 ± 2 events/h; P = .002). CFD modeling showed significant positive Pearson correlations between reduction of retropalatal airflow velocity and AHI (r = 0.617, P = .04) and ODI (r = 0.773, P = .005).AHI and ODI improvement after MMA is best correlated with (1) decreased retropalatal airflow velocity modeled by CFD and (2) increased lateral pharyngeal wall stability based on VOTE scoring from DISE.

    View details for DOI 10.1177/0194599815611603

    View details for PubMedID 26740522

  • Lateral Pharyngeal Wall Tension After Maxillomandibular Advancement for Obstructive Sleep Apnea Is a Marker for Surgical Success: Observations From Drug-Induced Sleep Endoscopy JOURNAL OF ORAL AND MAXILLOFACIAL SURGERY Liu, S. Y., Huon, L., Powell, N. B., Riley, R., Cho, H. G., Torre, C., Capasso, R. 2015; 73 (8): 1575-1582


    The efficacy of maxillomandibular advancement (MMA) for obstructive sleep apnea (OSA) with anatomic airway changes has previously been studied using static imaging and endoscopy in awake subjects. The aim of the present study was to use drug-induced sleep endoscopy (DISE) to evaluate the dynamic upper airway changes in sleeping subjects before and after MMA and their association with the surgical outcome.This was a retrospective cohort study of subjects with OSA who had undergone MMA at the Stanford University Sleep Surgery Division from July 2013 to July 2014. The subjects were included if perioperative polysomnography and DISE had been performed. The predictor variable was the perioperative DISE velum-oropharynx-tongue-epiglottis score. The outcome variables were the apnea-hypopnea index (AHI), oxygen-desaturation index (ODI), and Epworth Sleepiness Scale (ESS). A subgroup analysis was performed for the subjects who had undergone primary and secondary MMA. The statistical analyses included Cronbach's α coefficient, the McNemar test, and the independent Student t test. The P value was set at <.01.A total of 16 subjects (15 males, 1 female) were included in the present study, with an average age of 47 ± 10.9 years and body mass index of 29.4 ± 5.1 kg/m(2). Significant post-MMA decreases were found in the AHI (from 59.8 ± 25.6 to 9.3 ± 7.1 events/hr) and ODI (from 45 ± 29.7 to 5.7 ± 4.1 events/hr; P < .001). Greater improvement in the AHI occurred in the primary MMA group (P = .022). The post-MMA change in airway collapse was most significant at the lateral pharyngeal wall (P = .001). The subjects with the most improvement in lateral pharyngeal wall collapsibility demonstrated the largest changes in the AHI (from 60.0 ± 25.6 events/hr to 7.5 ± 3.4 events/hr) and ODI (from 46.7 ± 29.8 to 5.3 ± 2 events/hr; P = .002).Using DISE, we observed that after MMA, the greatest reduction in upper airway collapsibility is seen at the lateral pharyngeal wall of the oropharynx, followed by the velum, and then the tongue base. The stability of the lateral pharyngeal wall is a marker of surgical success after MMA using the AHI, ODI, and ESS.

    View details for DOI 10.1016/j.joms.2015.01.028

    View details for Web of Science ID 000357878600022

    View details for PubMedID 25843814

  • Static Craniofacial Measurements and Dynamic Airway Collapse Patterns Associated with Severe Obstructive Sleep Apnea: A Sleep MRI Study. Clinical otolaryngology : official journal of ENT-UK ; official journal of Netherlands Society for Oto-Rhino-Laryngology & Cervico-Facial Surgery Liu, S. Y., Huon, L. K., Lo, M. T., Chang, Y. C., Capasso, R., Chen, Y. J., Shih, T. T., Wang, P. C. 2015


    Using sleep MRI, we aimed to identify static craniofacial measurements and dynamic upper airway collapse patterns associated with severe obstructive sleep apnea (OSA) during natural sleep in age and BMI matched patients.Nested case-control study.Sleep MRI images (3.0 Tesla scanner) and synchronized acoustic recording were used to observe patterns of dynamic airway collapse in subjects with mild and severe OSA. Mid-sagittal images were also used for static craniofacial measurements.15 male subjects with severe OSA (mean AHI 70.3±23 events/hour) were matched by age and BMI to 15 subjects with mild OSA (mean AHI 7.8±1.4 events/hour). Subjects were selected from a consecutive sleep MRI study cohort.Static craniofacial measurements selected a priori included measurements that represent maxillomandibular relationships and airway morphology. Axial, sagittal, and coronal views of the airway were rated for dynamic collapse at retropalatal, retroglossal, and lateral pharyngeal wall regions by blinded reviewers. Bivariate analysis was used to correlate measures associated with severity of OSA using AHI. Statistical significance was set at p < 0.01.Lateral pharyngeal wall collapse from dynamic sleep MRI (ß=51.8, p<0.001) and upper airway length from static MRI images (ß=27.2, p<0.001) positively correlated with severity of OSA.Lateral pharyngeal wall collapse and upper airway length are significantly associated with severe OSA based on sleep MRI. Assessment of these markers can be readily translated to routine clinical practice, and their identification may direct targeted surgical treatment. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1111/coa.12598

    View details for PubMedID 26615985

  • Comparison of functional outcomes and patient-reported satisfaction between titanium and absorbable plates and screws for fixation of mandibular fractures: A one-year prospective study. Journal of cranio-maxillo-facial surgery : official publication of the European Association for Cranio-Maxillo-Facial Surgery Leno, M. B., Liu, S. Y., Chen, C. T., Liao, H. T. 2017


    The aim of this study is to compare the 1-year functional outcomes and patient-reported satisfaction in treating mandibular fractures between resorbable and titanium fixation devices.A 1-year prospective study was conducted; 41 consecutive patients presenting with mandibular fractures were included. A resorbable system was used in 21 patients, while in 20 patients a titanium fixation device was used. Functional outcome was evaluated objectively at several time points (2, 4 and 6 weeks, 3 and 6 months, and 1 year after surgery). Bite forces over molars and incisors, mouth opening distance, occlusal status, operation time, fee for implants, bone healing and plate-associated complications were evaluated. Functional and overall satisfaction was measured by patients themselves subjectively.A statistical difference was found only in maximal mouth opening and molar bite force, both greater for the titanium group in the 2-week time point, achieving comparable measurements in subsequent ones. This coincides with the patient-reported statistically lower satisfaction rates. The cost of the resorbable device was nearly 3 times more expensive than the titanium devices.Resorbable fixation can achieve stability of bone healing at 1 year postoperatively, with functional and satisfaction outcomes comparable to those associated with titanium hardware from the fourth week postoperatively, while yielding unique advantages.

    View details for DOI 10.1016/j.jcms.2017.01.034

    View details for PubMedID 28318918

  • Toward a functional definition of ankyloglossia: validating current grading scales for lingual frenulum length and tongue mobility in 1052 subjects. Sleep & breathing = Schlaf & Atmung Yoon, A., Zaghi, S., Weitzman, R., Ha, S., Law, C. S., Guilleminault, C., Liu, S. Y. 2017


    Alterations of the lingual frenulum may contribute to oromyofacial dysfunction, speech and swallowing impediments, underdevelopment of the maxillofacial skeleton, and even predispose to sleep breathing disorder. This study aims to assess the utility of existing instruments for evaluation of restricted tongue mobility, describe normal and abnormal ranges of tongue mobility, and provide evidence in support of a reliable and efficient measure of tongue mobility.A prospective cohort study of 1052 consecutive patients was evaluated during a 3-month period. Age, gender, ethnicity, height, weight, BMI, maximal interincisal mouth opening (MIO), mouth opening with tongue tip to maxillary incisive papillae at roof of mouth (MOTTIP), Kotlow's free-tongue measurement, and presence of severe tongue-tie were recorded. Secondary outcome measures include tongue range of motion deficit (TRMD, difference between MIO and MOTTIP) and tongue range of motion ratio (TRMR, ratio of MOTTIP to MIO).Results indicate that MIO is dependent on age and height; MOTTIP and TRMD are dependent on MIO; Kotlow's free-tongue measurement is an independent measure of free-tongue length and tongue mobility. TRMR is the only independent measurement of tongue mobility that is directly associated with restrictions in tongue function.We propose the use of tongue range of motion ratio as an initial screening tool to assess for restrictions in tongue mobility. "Functional" ankyloglossia can thus be defined and treatment effects followed objectively by using the proposed grading scale: grade 1: tongue range of motion ratio is >80%, grade 2 50-80%, grade 3 < 50%, grade 4 < 25%.

    View details for DOI 10.1007/s11325-016-1452-7

    View details for PubMedID 28097623

  • Sleep Surgery in the Elderly. Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery Gouveia, C. J., Cramer, J. D., Liu, S. Y., Capasso, R. 2017: 194599817691475


    Objective Assess the frequency and nature of postoperative complications following sleep surgery. Examine these issues specifically in elderly patients to provide guidance for their perioperative care. Study Design Retrospective cohort study. Setting American College of Surgeons National Surgical Quality Improvement Program. Methods We identified patients with obstructive sleep apnea undergoing sleep surgery procedures from 2006 to 2013 in the American College of Surgeons National Surgical Quality Improvement Program, a multi-institutional outcomes program designed to improve surgical quality. We analyzed patients by comparing age groups: <65 and ≥65 years. Summary data were analyzed, and multivariate regression was used to adjust for patient characteristics, comorbidities, and surgical procedure. Results We identified 2230 patients who had sleep surgery, which included 2123 patients <65 years old and 107 patients ≥65 years old. Elderly patients were significantly more likely to have hypertension requiring medication ( P < .001) and higher American Society of Anesthesiologists scores ( P < .001). There were no significant differences in the rates of nasal ( P = .87), palate ( P = .59), tongue base ( P = .73), and multilevel ( P = .95) surgery being performed on both groups of patients. Elderly patients had higher rates of wound complications and urinary tract infections as compared with younger patients. On multivariate analysis, age ≥65 was significantly associated with complications from sleep surgery (odds ratio, 2.35; 95% CI, 1.04-5.35). Conclusion Elderly patients undergoing sleep surgery have increased postoperative complication risk as compared with younger patients treated similarly. This information can help direct quality improvement efforts in the care of older patients.

    View details for DOI 10.1177/0194599817691475

    View details for PubMedID 28195824

  • Tongue retaining devices for obstructive sleep apnea: A systematic review and meta-analysis. American journal of otolaryngology Chang, E. T., Fernandez-Salvador, C., Giambo, J., Nesbitt, B., Liu, S. Y., Capasso, R., Kushida, C. A., Camacho, M. 2017


    Tongue Retaining Devices (TRD) anteriorly displace the tongue with suction forces while patients sleep. TRD provide a non-surgical treatment option for patients with Obstructive Sleep Apnea (OSA). Our objective was to conduct a systematic review of the international literature for TRD outcomes as treatment for OSA.Three authors independently and systematically searched four databases (including PubMed/MEDLINE) through June 26, 2016. We followed guidelines set within the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).Sixteen studies with 242 patients met criteria. The overall means±standard deviations (M±SD) for apnea-hypopnea index (AHI) decreased from 33.6±21.1/h to 15.8±16.0/h (53% reduction). Seven studies (81 patients) reported lowest oxygen saturation (LSAT), which improved from 79.8±17.5% to 83.9±8.6%. Four studies (93 patients) reported Epworth sleepiness scale (ESS), which decreased from 10.8±4.8 to 8.2±4.5, p <0.0001. Four studies (31 patients) reported Oxygen Desaturation Index (ODI) which decreased from 29.6±32.1 to 12.9±8.7, a 56.4% reduction.Current international literature demonstrates that tongue retaining devices reduce apnea-hypopnea index by 53%, increase lowest oxygen saturation by 4.1 oxygen saturation points, decrease oxygen desaturation index by 56% and decrease Epworth sleepiness scale scores by 2.8 points. Tongue retaining devices provide a statistically effective alternative treatment option for obstructive sleep apnea.

    View details for DOI 10.1016/j.amjoto.2017.01.006

    View details for PubMedID 28237516

  • Impact of Continuous Positive Airway Pressure in Patients with Obstructive Sleep Apnea During Drug Induced Sleep Endoscopy. Clinical otolaryngology : official journal of ENT-UK ; official journal of Netherlands Society for Oto-Rhino-Laryngology & Cervico-Facial Surgery Torre, C., Liu, S. Y., Kushida, C. A., Nekhendzy, V., Huon, L. K., Capasso, R. 2017


    The primary objective of the study was to understand the differential impact of Continuous Positive Airway Pressure (CPAP) on the location, degree, and pattern of airway collapse in Obstructive Sleep Apnea (OSA) patients utilizing Drug Induced Sleep Endoscopy (DISE).Non-randomized trial.University Medical Center.15 consecutive OSA patients undergoing DISE.The patterns of airway collapse were videorecorded at baseline and under differential application of nasal CPAP (nCPAP) at 5,10, and 15 cm H2 O. For each modality, the pattern and degree of airway collapse were analyzed by three independent observers using the Velum, Oropharynx, Tongue Base, Epiglottis (VOTE) classification system.The modest nCPAP pressures (10cm H2 O) had the greatest impact on the lateral walls of the pharynx, followed by the palatal region. The collapsibility of the tongue base and epiglottis demonstrated significant resistance to nCPAP application, which was overcome by increasing nCPAP to 15 cm H2 O. Compared to 5 cm H2 O, nCPAP pressures of 10 and 15 cm H2 O improved complete collapse at least at one level of the upper airway (p = 0.016 and 0.001, respectively). Increased nCPAP pressures also led to changes in the configuration of airway collapse at the level of the velum.The differential nCPAP effects observed in this study may help to understand some of the mechanisms responsible for inadequate patient response and poor nCPAP compliance. The use of DISE in combination with CPAP may serve as a first step in optimizing patients that failed to adapt to treatment with CPAP. This approach can help the physician identify patterns of airway collapse that may require varying pressures different from the one the patient is using, as well as anatomical factors that may be corrected to help with compliance. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1111/coa.12851

    View details for PubMedID 28207995

  • Dynamic upper airway collapse observed from sleep MRI: BMI-matched severe and mild OSA patients EUROPEAN ARCHIVES OF OTO-RHINO-LARYNGOLOGY Huon, L., Liu, S. Y., Shih, T. T., Chen, Y., Lo, M., Wang, P. 2016; 273 (11): 4021-4026


    Dynamic magnetic resonance imaging (MRI) allows real-time characterization of upper airway collapse in sleeping subjects with obstructive sleep apnea (OSA). The aim of our study was to use sleep MRI to compare differences in upper airway collapse sites between BMI-matched subjects with mild OSA and severe OSA. This is a prospective, nested case-control study using dynamic sleep MRI to compare 15 severe OSA subjects (AHI >40) and 15 mild OSA (AHI <10) subjects, who were matched for BMI. Upper airway imaging was performed on sleeping subjects in a 3.0 T MRI scanner. Sleep MRI movies were used by blinded reviewers to identify retropalatal (RP), retroglossal (RG), and lateral pharyngeal wall (LPW) airway collapse. Mean AHI in the severe OSA group was 70.3 ± 23 events/h, and in the mild group was 7.8 ± 1 events/h (p < 0.001). All mild and severe OSA subjects demonstrated retropalatal airway collapse. Eighty percent in the mild group showed single-level RP collapse (p < 0.001). All subjects in the severe group showed multi-level collapse: RP + LPW (n = 9), RP + RG + LPW (n = 6). All severe OSA subjects showed LPW collapse, as compared with three subjects in the mild group (p < 0.001). LPW collapse was positively associated with AHI in simple regression analysis (β = 51.8, p < 0.001). In conclusion, severe OSA patients present with more lateral pharyngeal wall collapse as compared to BMI-matched mild OSA patients.

    View details for DOI 10.1007/s00405-016-4131-1

    View details for Web of Science ID 000385202600071

    View details for PubMedID 27276991

  • Inferior alveolar nerve hemangioma. Laryngoscope Vaezeafshar, R., Liu, S. Y., Sidell, D. 2016; 126 (9): 2168-2170


    A 14-year-old male presented with lower lip numbness and a slowly enlarging mandibular mass. Computed tomography demonstrated an expansile lesion centered in the marrow space of the left mandibular body, extending along the course of the inferior alveolar nerve (IAN), and expanding the mental foramen. Preoperative diagnosis was consistent with an IAN schwannoma. Surgical planning was performed using PROPLAN CMF software. The lesion was approached via a sagittal split osteotomy and excised en bloc with the IAN. Final pathology demonstrated a capillary hemangioma originating from the inferior alveolar nerve. Based on a detailed PubMed search, this is the first capillary hemangioma of the inferior alveolar nerve reported in the literature.NA Laryngoscope, 2016.

    View details for DOI 10.1002/lary.25869

    View details for PubMedID 26863892

  • Supraglottoplasty for laryngomalacia with obstructive sleep apnea: A systematic review and meta-analysis LARYNGOSCOPE Camacho, M., Dunn, B., Torre, C., Sasaki, J., Gonzales, R., Liu, S. Y., Chan, D. K., Certal, V., Cable, B. B. 2016; 126 (5): 1246-1255


    To determine if apnea-hypopnea index (AHI) and lowest oxygen saturation (LSAT) improve following isolated supraglottoplasty for laryngomalacia with obstructive sleep apnea (OSA) in children.Systematic review and meta-analysis.Nine databases, including PubMed/MEDLINE, were searched through September 30, 2015.A total of 517 studies were screened; 57 were reviewed; and 13 met criteria. One hundred thirty-eight patients were included (age range: 1 month-12.6 years). Sixty-four patients had sleep exclusive laryngomalacia, and in these patients: 1) AHI decreased from a mean (M) ± standard deviation (SD) of 14.0 ± 16.5 (95% confidence interval [CI] 10.0, 18.0) to 3.3 ± 4.0 (95% CI 2.4, 4.4) events/hour (relative reduction: 76.4% [95% CI 53.6, 106.4]); 2) LSAT improved from a M ± SD of 84.8 ± 8.4% (95% CI 82.8, 86.8) to 87.6 ± 4.4% (95% CI 86.6, 88.8); 3) standardized mean differences (SMD) demonstrated a small effect for LSAT and a large effect for AHI; and 4) cure (AHI < 1 event/hour) was 10.5% (19 patients with individual data). Seventy-four patients had congenital laryngomalacia, and in these patients: 1) AHI decreased from a M ± SD of 20.4 ± 23.9 (95% CI 12.8, 28.0) to 4.0 ± 4.5 (95% CI 2.6, 5.4) events/hour (relative reduction: 80.4% [95% CI 46.6, 107.4]); 2) LSAT improved from a M ± SD of 74.5 ± 11.9% (95% CI 70.9, 78.1) to 88.4 ± 6.6% (95% CI 86.4, 90.4); 3) SMD demonstrated a large effect for both AHI and LSAT; and 4) cure was 26.5% (38 patients with individual data).Supraglottoplasty has improved AHI and LSAT in children with OSA and either sleep exclusive laryngomalacia or congenital laryngomalacia; however, the majority of them are not cured. Laryngoscope, 2015.

    View details for DOI 10.1002/lary.25827

    View details for Web of Science ID 000374769400046

    View details for PubMedID 26691675

  • Epiglottis collapse in adult obstructive sleep apnea: A systematic review. Laryngoscope Torre, C., Camacho, M., Liu, S. Y., Huon, L., Capasso, R. 2016; 126 (2): 515-523


    To systematically review the international literature evaluating the role of the epiglottis in snoring and obstructive sleep apnea and to explore possible treatment options available.PubMed, Scopus, Embase, Google Scholar, Book Citation Index-Science, CINAHL, Conference Proceedings Citation Index-Science, The Cochrane Collaboration Databases, and Web of Science.The searches were performed from the first year of each database through March 5, 2015.Fourteen studies about the prevalence of epiglottis collapse in obstructive sleep apnea (OSA) were found. Most involved drug-induced sleep endoscopy studies that indirectly reported their findings about epiglottis collapse. The data suggests that the prevalence of epiglottis collapse in OSA is higher than previously described. The epiglottis has been implicated in 12% of cases of snoring, and sound originating from it has a higher pitch than palatal snoring. Continuous positive pressure (CPAP) surgery and positional therapy in the treatment of epiglottis collapse were also considered. Lateral position of the head may reduce the frequency of epiglottis collapse. With regard to CPAP, available reports suggest that it may accentuate collapse of the epiglottis. Surgery may help reduce snoring in some patients with a lax epiglottis and improve OSA in patients undergoing multilevel surgery.Knowledge regarding the role of the epiglottis in adult OSA and snoring patients is limited. The prevalence of this phenomenon in OSA seems to be greater than previously reported, and more research is needed to understand its role in OSA and the best way to treat it.NA. Laryngoscope, 2015.

    View details for DOI 10.1002/lary.25589

    View details for PubMedID 26371602

  • Hyoid surgery alone for obstructive sleep apnea: A systematic review and meta-analysis. The Laryngoscope Song, S. A., Wei, J. M., Buttram, J., Tolisano, A. M., Chang, E. T., Liu, S. Y., Certal, V., Camacho, M. 2016


    The primary objective was to determine if sleep study variables (e.g., apnea-hypopnea index [AHI] and lowest oxygen saturation) and quantitative sleepiness data improve following isolated hyoid surgery for obstructive sleep apnea (OSA).Systematic review and meta-analysis.Nine databases, including PubMed, were searched through September 5, 2015.Four hundred ninety-eight studies were screened, 64 were reviewed, and nine studies met inclusion criteria. A total of 101 patients were identified who underwent hyoid surgery alone for treatment of OSA. Subanalyses were performed for: 1) type of surgery, 2) primary versus secondary hyoid surgery, 3) positional versus nonpositional OSA, 4) age, and 5) body mass index. In patients undergoing isolated hyoid surgery, the AHI decreased from a mean ± standard deviation of 37.3 ± 21.1 (95% confidence interval [CI]: 33.1, 41.5) to 23.0 ± 18.6 (95% CI: 19.3, 26.7) events/hour, which correspond to a 38.3% reduction (P < .0001). AHI reduced by 38.3% for hyoid myotomy with suspension, by 50.7% for hyothyroidopexy, and by 7.1% for hyoid expansion. The Epworth Sleepiness Scale decreased by 3.2 points from 10.3 ± 4.9 (95% CI: 8.8, 11.8) to 7.1 ± 4.2 (95% CI: 5.8, 8.4; P = .0027).Isolated hyoid surgery has reduced OSA severity and improved sleepiness in adults. Hyothyroidopexy provided a 50.7% reduction in AHI, followed by hyoid myotomy with suspension (38.3% reduction in AHI) and hyoid expansion (7.1% reduction in AHI). The current literature lacks high-quality evidence with regard to hyoid surgery, and additional studies are needed to further elucidate the effect of hyoid surgery in OSA.NA Laryngoscope, 2015.

    View details for DOI 10.1002/lary.25847

    View details for PubMedID 26801005

  • Subtypes of Maxillomandibular Advancement Surgery for Patients With Obstructive Sleep Apnea. The Journal of craniofacial surgery Lee, W. J., Hwang, D. H., Liu, S. Y., Kim, S. J. 2016; 27 (8): 1965–70


    Maxillomandibular advancement (MMA) surgery, which is the most effective treatment modality for patients with moderate-to-severe obstructive sleep apnea with apparent skeletal discrepancies, has been modified in conjunction with segmental osteotomies, counterclockwise rotation of maxillomandibular complex, and other adjunctive procedures. However, any single type of MMA could not treat or cure all the patients with obstructive sleep apnea showing different dentofacial and pharyngeal patterns. We aimed to suggest critical decision factors for the selective application of MMA subtypes, categorized as straight MMA with genioplasty, rotational MMA, segmental MMA, and segmental-rotational MMA, in the surgical treatment objective process: anteroposterior position of maxilla, upper lip projection, overjet, lower incisor inclination as sagittal factors, and upper incisor exposure and occlusal plane angle as vertical factors. This case series deserves a clinical basis on the way of case-by-case application of the optimal MMA subtype based on the successful treatment outcomes with short-term stability.

    View details for DOI 10.1097/SCS.0000000000003027

    View details for PubMedID 28005735

  • A safe and accurate method to perform esthetic mandibular contouring surgery for Far Eastern Asians. International journal of oral and maxillofacial surgery Hsieh, A. M., Huon, L. K., Jiang, H. R., Liu, S. Y. 2016


    A tapered mandibular contour is popular with Far Eastern Asians. This study describes a safe and accurate method of using preoperative virtual surgical planning (VSP) and an intraoperative ostectomy guide to maximize the esthetic outcomes of mandibular symmetry and tapering while mitigating injury to the inferior alveolar nerve (IAN). Twelve subjects with chief complaints of a wide and square lower face underwent this protocol from January to June 2015. VSP was used to confirm symmetry and preserve the IAN while maximizing the surgeon's ability to taper the lower face via mandibular inferior border ostectomy. The accuracy of this method was confirmed by superimposition of the perioperative computed tomography scans in all subjects. No subjects complained of prolonged paresthesia after 3 months. A safe and accurate protocol for achieving an esthetic lower face in indicated Far Eastern individuals is described.

    View details for DOI 10.1016/j.ijom.2016.11.015

    View details for PubMedID 27993447

  • Genial tubercle advancement and genioplasty for obstructive sleep apnea: A systematic review and meta-analysis. The Laryngoscope Song, S. A., Chang, E. T., Certal, V., Del Do, M., Zaghi, S., Liu, S. Y., Capasso, R., Camacho, M. 2016


    To perform a systematic review and meta-analysis for studies evaluating genioplasty alone, genial tubercle advancement (GTA) alone, and GTA with hyoid surgery (GTA-HS) to treat obstructive sleep apnea (OSA).Ten databases.Three authors searched through November 15, 2015.1,207 studies were screened; 69 were downloaded; and 13 studies met inclusion criteria. A total of 111 patients were included, with 27 standard genioplasty, 10 modified genioplasty, 24 GTA, and 50 GTA-HS patients. For standard genioplasty, the apnea-hypopnea index (AHI) reduced from a mean ± standard deviation (M ± SD) of 18.8 ± 3.8 (95% confidence interval [CI] 17.6, 20.0) to 10.8 ± 4.0 (95% CI 9.5, 12.1) events/hour (relative reduction 43.8%), P value = 0.0001. Genioplasty improved lowest oxygen saturation (LSAT) from 82.3 ± 7.3% (95% CI 80.0, 84.7) to 86.8 ± 5.2% (95% CI 85.1, 88.5), P value = 0.0032. For modified genioplasty AHI increased by 37.3%. For GTA, the AHI reduced from an M ± SD of 37.6 ± 24.2 (95% CI 27.9, 47.3) to 20.4 ± 15.1 (95% CI 14.4, 26.4) events/hour (relative reduction 45.7%), P value = 0.0049. GTA improved LSAT from 83.1 ± 8.3% (95% CI 79.8, 86.4) to 85.5 ± 6.8% (95% CI 82.8, 88.2), P value = 0.2789. For GTA-HS, the AHI reduced from an M ± SD of 34.5 ± 22.1 (95% CI 28.4, 40.6) to 15.3 ± 17.6 (95% CI 10.4, 20.2) events/hour (relative reduction 55.7%), P value < 0.0001; GTA-HS improved LSAT from 80.1 ± 16.6% (95% CI 75.5, 84.7) to 88.3 ± 6.9% (95% CI 86.4, 90.2), P value = 0.0017.Standard genioplasty, GTA and GTA-HS can improve OSA outcomes such as AHI and LSAT. Given the low number of studies, these procedures remain as an area for additional OSA research. Laryngoscope, 2016.

    View details for DOI 10.1002/lary.26218

    View details for PubMedID 27546467

  • Transpalatal advancement pharyngoplasty for obstructive sleep apnea: a systematic review and meta-analysis. European archives of oto-rhino-laryngology : official journal of the European Federation of Oto-Rhino-Laryngological Societies (EUFOS) : affiliated with the German Society for Oto-Rhino-Laryngology - Head and Neck Surgery Volner, K., Dunn, B., Chang, E. T., Song, S. A., Liu, S. Y., Brietzke, S. E., O'Connor, P., Camacho, M. 2016


    The objective is to determine if apnea-hypopnea index (AHI) and lowest oxygen saturation (LSAT) improve after transpalatal advancement pharyngoplasty (TPAP) with obstructive sleep apnea (OSA) in adults, using a systematic review and meta-analysis. Nine databases, including PubMed/MEDLINE, were searched through April 1, 2016. All studies that included patients who underwent TPAP alone were included in this analysis. Fifty-six studies were potentially relevant, 37 were downloaded and five studies met criteria with 199 patients (age: 42.5 ± 9.7 years and body mass index: 29.0 ± 4.0 kg/m(2)). The grand mean (M) and standard deviation (SD) for AHI (199 patients) pre and post-TPAP decreased from 54.6 ± 23.0 [95 % CI 51.4, 57.8] to 19.2 ± 16.8 [95 % CI 16.9, 21.5] events/h (relative reduction: 64.8 %). Random effects modeling demonstrated a mean difference (MD) of -36.3 [95 % CI -48.5, -24.1], overall effect Z = 5.8 (p < 0.00001), and I (2) = 85 % (significant inconsistency). The standardized mean difference (SMD) for TPAP demonstrated a large magnitude of effect for AHI -1.76 [95 % CI -2.4, -1.1]. For LSAT (70 patients), the pre and post-TPAP M ± SD improved from 81.9 ± 8.1 [95 % CI 80.0, 83.8] to 85.4 ± 6.9 [95 % CI 83.8, 87.0], with a MD of 3.55, overall effect Z = 1.79 (p = 0.07). Thus far, few studies have evaluated transpalatal advancement pharyngoplasty; therefore, we recommend additional studies, especially prospective studies. Research comparing TPAP to pharyngoplasty procedures without palatal advancement would help determine the optimal role for this procedure.

    View details for DOI 10.1007/s00405-016-4121-3

    View details for PubMedID 27289234

  • The association between ophthalmologic diseases and obstructive sleep apnea: a systematic review and meta-analysis. Sleep & breathing = Schlaf & Atmung Huon, L. K., Liu, S. Y., Camacho, M., Guilleminault, C. 2016


    The purpose of this study was to evaluate the association between obstructive sleep apnea (OSA) and ophthalmologic diseases, specifically glaucoma, nonarteritic anterior ischemic optic neuropathy (NAION), retinal vein occlusion (RVO), central serous chorioretinopathy (CSR), and floppy eyelid syndrome (FES), by performing a systematic review and meta-analysis of published studies.PubMed, Embase, and Scopus databases were searched for observational studies on OSA and its association with select ophthalmologic diseases. Data was pooled for random-effects modeling. The association between OSA and ophthalmologic diseases was summarized using an estimated pooled odds ratio with a 95 % confidence interval.Relative to non-OSA subjects, OSA subjects have increased odds of diagnosis with glaucoma (pooled odds ratio (OR) = 1.242; P < 0.001) and floppy eyelids syndrome (pooled OR = 4.157; P < 0.001). In reverse, the overall pooled OR for OSA was 1.746 (P = 0.002) in the glaucoma group, 3.126 (P = 0.000) in the NAION group, and 2.019 (P = 0.028) in the CSR group. For RVO, one study with 5965 OSA patients and 29,669 controls demonstrated a 1.94-fold odds increase in OSA patients.Our results suggest significant associations between OSA and glaucoma, NAION, CSR, and FES. Screening for OSA should be considered in patients with glaucoma, NAION, CSR, or FES.

    View details for DOI 10.1007/s11325-016-1358-4

    View details for PubMedID 27230013

  • Lateral Pharyngeal Wall Collapse Associated With Hypoxemia in Obstructive Sleep Apnea LARYNGOSCOPE Lan, M., Liu, S. Y., Lan, M., Modi, R., Capasso, R. 2015; 125 (10): 2408-2412


    Review drug-induced sleep endoscopy (DISE) findings and correlate the patterns of airway collapse with body mass index (BMI) and objective sleep study respiratory variables, with particular emphasis on oxygen desaturation variables.Retrospective chart review.From January 2010 to March 2014, 64 patients underwent DISE, and its findings were registered using the VOTE (velum, oropharynx, tongue base, epiglottis) classification system. Associations were analyzed between DISE, BMI, and polysomnographic parameters.Complete lateral oropharyngeal collapse was significantly associated with increased severity of obstructive sleep apnea (OSA), reflected by a higher oxygen desaturation index, apnea-hypopnea index, apnea index, the percent of the total time with oxygen saturation level lower than 90%, and minimal oxygen saturation). Complete concentric collapse of the velum and complete lateral oropharyngeal collapse were associated with higher BMI values.The results of this study demonstrate a strong association between complete lateral oropharyngeal wall collapse and increased OSA severity, particularly with objective oximetry measures. Patients with a complete lateral oropharyngeal wall collapse may need aggressive treatment strategies because of the high probability of subsequent cardiovascular complications.4 Laryngoscope, 2015.

    View details for DOI 10.1002/lary.25126

    View details for Web of Science ID 000363386300044

    View details for PubMedID 25582498

  • Large maxillomandibular advancements for obstructive sleep apnea: An operative technique evolved over 30 years JOURNAL OF CRANIO-MAXILLOFACIAL SURGERY Camacho, M., Liu, S. Y., Certal, V., Capasso, R., Powell, N. B., Riley, R. W. 2015; 43 (7): 1113-1118


    Obstructive sleep apnea (OSA) can be a challenging disorder to treat. Maxillomandibular advancements (MMAs) generally have high success rates; however, larger advancements have higher success and cure rates. Our aim is to present and to describe the current technique used by the senior authors, which has been successful for performing large advancements, thereby improving post-operative outcomes.The senior authors have developed and modified their maxillomandibular advancement operative techniques significantly over the past 30 years. The current version of the Riley-Powell MMA technique is described in a step-by-step fashion in this article.Initially, as part of the MMAs, patients underwent maxillomandibular fixation with wires, lag screws and harvested split calvarial bone grafts. The current technique utilizes plates, screws, Erich Arch Bars, and suspension wires which are left in place for 5-6 weeks. Guiding elastics are worn for the first week. The MMA technique described in this article has yielded a success rate over 90% for patients with a body mass index (BMI) <40 kg/m(2) and 81% for patients with a BMI ≥40 kg/m(2).Large advancements during maxillomandibular advancement surgeries can help improve post-operative obstructive sleep apnea outcomes.

    View details for DOI 10.1016/j.jcms.2015.05.015

    View details for Web of Science ID 000361078700023

    View details for PubMedID 26116307

  • Inferior Turbinate Classification System, Grades 1 to 4: Development and Validation Study LARYNGOSCOPE Camacho, M., Zaghi, S., Certal, V., Abdullatif, J., Means, C., Acevedo, J., Liu, S., Brietzke, S. E., Kushida, C. A., Capasso, R. 2015; 125 (2): 296-302


    To develop a validated inferior turbinate grading scale.Development and validation study.Phase 1 development (alpha test) consisted of a proposal of 10 different inferior turbinate grading scales (>1,000 clinic patients). Phase 2 validation (beta test) utilized 10 providers grading 27 standardized endoscopic photos of inferior turbinates using two different classification systems. Phase 3 validation (pilot study) consisted of 100 live consecutive clinic patients (n = 200 inferior turbinates) who were each prospectively graded by 18 different combinations of two independent raters, and grading was repeated by each of the same two raters, two separate times for each patient.In the development phase, 25% (grades 1-4) and 33% (grades 1-4) were the most useful systems. In the validation phase, the 25% classification system was found to be the best balance between potential clinical utility and ability to grade; the photo grading demonstrated a Cohen's kappa (κ) = 0.4671 ± 0.0082 (moderate inter-rater agreement). Live-patient grading with the 25% classification system demonstrated an overall inter-rater reliability of 71.5% (95% confidence interval [CI]: 64.8-77.3), with overall substantial agreement (κ = 0.704 ± 0.028). Intrarater reliability was 91.5% (95% CI: 88.7-94.3). Distribution for the 200 inferior turbinates was as follows: 25% quartile = grade 1, 50% quartile (median) = grade 2, 75% quartile = grade 3, and 90% quartile = grade 4. Mean turbinate size was 2.22 (95% CI: 2.07-2.34; standard deviation 1.02). Categorical κ was as follows: grade 1, 0.8541 ± 0.0289; grade 2, 0.7310 ± 0.0289; grade 3, 0.6997 ± 0.0289, and grade 4, 0.7760 ± 0.0289.The 25% (grades 1-4) inferior turbinate classification system is a validated grading scale with high intrarater and inter-rater reliability. This system can facilitate future research by tracking the effect of interventions on inferior turbinates.2c Laryngoscope, 2014.

    View details for DOI 10.1002/lary.24923

    View details for Web of Science ID 000349973400016

  • Anterior Mandibular Fractures Atlas of Oral and Maxillofacial Surgery Bast, B., Liu, S. Elsevier Saunders. 2015: 680-687
  • Advancements in office-based anesthesia in oral and maxillofacial surgery. Atlas of the oral and maxillofacial surgery clinics of North America Robert, R. C., Liu, S., Patel, C., Gonzalez, M. L. 2013; 21 (2): 139-165

    View details for DOI 10.1016/j.cxom.2013.05.007

    View details for PubMedID 23981491

  • Surgical Care of the Hemifacial Microsomia Patient Current Therapy in Oral and Maxillofacial Surgery Liu, S., Good, P., Lee, J. S. Elsevier. 2012: 828-834


    Surgical resection of oral cancer can be associated with significant postoperative cardiovascular and respiratory complications that require more sensitive predictors.All patients with oral squamous cell carcinoma treated from July 2005 to April 2008 were retrospectively reviewed. The Goldman Revised Cardiac Risk Index (GRCRI) was used to predict cardiovascular complications. Other evidence-based a priori predictors were applied in an h-fold cross-validation model.Operating room (OR) time was an independent predictor of cardiovascular complications (odds ratio = 1.54, p = .002, 95% confidence interval [CI] = 1.18-2.02) and respiratory complications (odds ratio = 1.3, p = .06, 95% CI = 0.99-1.64) after multivariate adjustment. OR time and estimated blood loss predicted cardiovascular complications with 73% sensitivity. The GRCRI achieved 37% sensitivity. OR time and tracheostomy predicted respiratory complications with 75% sensitivity.The GRCRI was not prognostic for cardiovascular complications in patients with oral cancer. The most sensitive predictors for cardiovascular complications were OR time and estimated blood loss; for respiratory complications they were OR time and tracheostomy.

    View details for DOI 10.1002/hed.21411

    View details for Web of Science ID 000286290400018

    View details for PubMedID 20578073

  • Peripheral endothelin A receptor antagonism attenuates carcinoma-induced pain EUROPEAN JOURNAL OF PAIN Schmidt, B. L., Pickering, V., Liu, S., Quang, P., Dolan, J., Connelly, S. T., Jordan, R. C. 2007; 11 (4): 406-414


    In this study we investigated the role of endothelin-1 (ET-1) and its peripheral receptor (ET-A) in carcinoma-induced pain in a mouse cancer pain model. Tumors were induced in the hind paw of female mice by local injection of cells derived from a human oral squamous cell carcinoma (SCC). Significant pain, as indicated by reduction in withdrawal thresholds in response to mechanical stimulation, began at four days after SCC inoculation and lasted to 28 days, the last day of measurement. Intra-tumor expression of both ET-1 mRNA and ET-1 protein were significantly upregulated compared to normal tissue, and local administration of the ET-A receptor selective antagonist, BQ-123 (100 microM) significantly elevated withdrawal thresholds, indicating the induction of an antinociceptive effect. These findings support the suggestion that ET-1 and ET-A receptors contribute to the severity of carcinoma-induced soft tissue cancer pain.

    View details for DOI 10.1016/j.ejpain.2006.05.007

    View details for Web of Science ID 000245544600006

    View details for PubMedID 16807013

  • Increased basal ganglia volumes in velo-cardio-facial syndrome (deletion 22q11.2) BIOLOGICAL PSYCHIATRY Eliez, S., Barnea-Goraly, N., Schmitt, J. E., Liu, Y., Reiss, A. L. 2002; 52 (1): 68-70


    This study evaluated differences in caudate volumes in subjects with velo-cardio-facial syndrome due to a 22q11.2 (22qDS) deletion. Because psychosis is observed in 30% of adult subjects with 22qDS, this neurogenetic disorder could represent a putative model for a genetically mediated subtype of schizophrenia.Caudate volumes were measured on high-resolution magnetic resonance images in 30 children and adolescents with 22qDS and 30 gender- and age-matched normal comparison subjects.Caudate head volumes were increased in the 22qDS group independent of neuroleptic medications. Subjects with 22qDS also displayed an abnormal pattern of asymmetry in the anterior caudate, with left side greater than right.Alterations in the basal ganglia circuitry have been implicated in learning, cognitive, and behavioral problems in children and therefore could be involved in the expression of the neurobehavioral phenotype expressed by subjects with 22qDS. Abnormal caudate volume is a neurodevelopmental feature shared with schizophrenia, further establishing 22qDS as a potential neurodevelopmental model for this disorder.

    View details for Web of Science ID 000176340700009

    View details for PubMedID 12079732

  • Reliability of the Muller maneuver and its association with sleep-disordered breathing Terris, D. J., Hanasono, M. M., Liu, Y. C. JOHN WILEY & SONS INC. 2000: 1819-1823


    Use of the Muller maneuver (MM) in the evaluation of patients with obstructive sleep apnea is controversial. One criticism of this test is that it is somewhat subjective. Our objective is to explore the reliability of this technique and its association with sleep-disordered breathing.Prospective study performed in an academic tertiary care center.An analysis of MM scores from 180 consecutive patients obtained independently by two examiners was completed. These scores were compared with each other and with the apnea-hypopnea index (AHI) obtained from polysomnographic studies.Collapse of the soft palate (PAL), lateral pharyngeal wall (LPW), and base of the tongue (BOT) was rated on a five-point scale (0-4). The mean scores determined by the faculty examiner were 2.47, 2.06, and 1.58, respectively; the mean scores determined by the resident examiner were 2.34, 2.25, and 1.48, respectively. The scores of the two examiners correlated to within +/- 1 unit 83.9% of the time at the PAL, 91.1% at the LPW, and 85.0% at the BOT. The degree of correlation was not influenced by year of training of the resident. When the AHI was converted to a four-point scale based on severity, the score correlated within +/- 1 of the average MM score 72.1% of the time.Despite the subjective nature of the MM, the five-point scale can be used by independent examiners to achieve an evaluation of the upper airway that is reproducible. The preoperative severity of sleep-disordered breathing based on the AHI is moderately correlated with the MM score.

    View details for Web of Science ID 000165165200009

    View details for PubMedID 11081592