Dr. Liu was born in Taiwan, grew up in Istanbul, and boarded at The Lawrenceville School before attending Stanford as an undergraduate student. He completed his medical and dental degrees at the University of California-San Francisco (UCSF), during which he spent one year at the NIH as a Howard Hughes Medical Institute (HHMI) Reseach Scholar, and another year as a UCSF fellow of Advanced Training in Clinical Research (ATCR). He continued his maxillofacial surgical training at UCSF, prior to becoming a clinical instructor (fellow) of Otolaryngology at Stanford focusing on surgery for obstructive sleep apnea.

During his instructor year at Stanford (2013-14), he operated as a co-surgeon on classic Stanford procedures (particularly maxillomandibular advancement - MMA) with Dr. Robert Riley, one of the pioneers of sleep apnea surgery. He also trained under Professor Yu-ray Chen and C.T. Chen of Taiwan's Chang Gung Plastic & Reconstructive Surgery program focusing on Surgery-First Orthognathic Surgery and treatment of complex primary and secondary facial trauma. He joined the faculty at the Stanford University School of Medicine as an Assistant Professor of Otolaryngology in 2014. He current serves as co-director of the Stanford Sleep Surgery Fellowship Program. He is also a preceptor of facial trauma for the Stanford Oculoplastic Surgery Fellowship.

Dr. Liu's focuses on the comprehensive surgical management of patients with obstructive sleep apnea. He also treats patients with congenital or acquired (traumatic) maxillofacial deformity. He has lectured in the U.S. and internationally on these topics, with emphasis on his research work related to sleep-disordered breathing.

Clinical Focus

  • Sleep Apnea, Obstructive
  • Sleep Apnea Surgery
  • Facial Trauma
  • Orthognathic Surgery
  • Otolaryngology

Academic Appointments

Honors & Awards

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

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)


All Publications

  • 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

  • Efficacy of Maxillomandibular Advancement Examined with Drug-induced Sleep Endoscopy and Computational Fluid Dynamics Airflow Modeling Otolaryngology-Head and Neck Surgery Liu, S. Y., Huon, L., Iwasaki, T., Powell, N., Riley, R., Torre, C., Capasso, R. 2015; ACCEPTED
  • Anterior Mandibular Fractures Atlas of Oral and Maxillofacial Surgery Bast, B., Liu, S. Elsevier Saunders. 2016: 680-687
  • 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 PubMedID 25215619

  • Large maxillomandibular advancements for obstructive sleep apnea: An operative technique evolved over 30 years. Journal of cranio-maxillo-facial surgery : official publication of the European Association for Cranio-Maxillo-Facial Surgery Camacho, M., Liu, S. Y., Certal, V., Capasso, R., Powell, N. B., Riley, R. W. 2015


    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 PubMedID 26116307

  • Epiglottis collapse in adult obstructive sleep apnea: A systematic review. The Laryngoscope Torre, C., Camacho, M., Liu, S. Y., Huon, L. K., Capasso, R. 2015


    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

  • Lateral pharyngeal wall collapse associated with hypoxemia in obstructive sleep apnea. The Laryngoscope Lan, M. C., Liu, S. Y., Lan, M. Y., Modi, R., Capasso, R. 2015


    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 PubMedID 25582498

  • 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

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