Paradoxical androgen receptor regulation by small molecule enantiomers.

Small molecules that target the androgen receptor (AR) are the mainstay of therapy for lethal castration-resistant prostate cancer (CRPC), yet existing drugs lose their efficacy during continued treatment. This evolution of resistance is due to heterogenous mechanisms which include AR mutations causing the identical drug to activate instead of inhibit the receptor. Understanding in molecular detail the paradoxical phenomenon wherein an AR antagonist is transformed into an agonist by structural mutations in the target receptor is thus of paramount importance. Herein, we describe a reciprocal paradox: opposing antagonist and agonist AR regulation determined uniquely by enantiomeric forms of the same drug structure. The antiandrogen BMS-641988, which has (R)-chirality at C-5 encompasses a previously uncharacterized (S)-stereoisomer that is, surprisingly, a potent agonist of AR, as demonstrated by transcriptional assays supported by cell imaging studies. This duality was reproduced in a series of novel compounds derived from the BMS-641988 scaffold. Coupled with in silico modeling studies, the results inform an AR model that explains the switch from potent antagonist to high-affinity agonist in terms of C-5 substituent steric interactions with helix 12 of the ligand binding site. They imply strategies to overcome AR drug resistance and demonstrate that insufficient enantiopurity in this class of AR antagonist can confound efforts to correlate structure with function.

Endosidin20 Targets the Cellulose Synthase Catalytic Domain to Inhibit Cellulose Biosynthesis.

Plant cellulose is synthesized by rosette-structured cellulose synthase (CESA) complexes (CSCs). Each CSC is composed of multiple subunits of CESAs representing three different isoforms. Individual CESA proteins contain conserved catalytic domains for catalyzing cellulose synthesis, other domains such as plant-conserved sequences, and class-specific regions that are thought to facilitate complex assembly and CSC trafficking. Because of the current lack of atomic-resolution structures for plant CSCs or CESAs, the molecular mechanism through which CESA catalyzes cellulose synthesis and whether its catalytic activity influences efficient CSC transport at the subcellular level remain unknown. Here, by performing chemical genetic analyses, biochemical assays, structural modeling, and molecular docking, we demonstrate that Endosidin20 (ES20) targets the catalytic site of CESA6 in Arabidopsis (Arabidopsis thaliana). Chemical genetic analysis revealed important amino acids that potentially participate in the catalytic activity of plant CESA6, in addition to previously identified conserved motifs across kingdoms. Using high spatiotemporal resolution live cell imaging, we found that inhibiting the catalytic activity of CESA6 by ES20 treatment reduced the efficiency of CSC transport to the plasma membrane. Our results demonstrate that ES20 is a chemical inhibitor of CESA activity and trafficking that represents a powerful tool for studying cellulose synthesis in plants.

Endosidin2 targets conserved exocyst complex subunit EXO70 to inhibit exocytosis.

The exocyst complex regulates the last steps of exocytosis, which is essential to organisms across kingdoms. In humans, its dysfunction is correlated with several significant diseases, such as diabetes and cancer progression. Investigation of the dynamic regulation of the evolutionarily conserved exocyst-related processes using mutants in genetically tractable organisms such as Arabidopsis thaliana is limited by the lethality or the severity of phenotypes. We discovered that the small molecule Endosidin2 (ES2) binds to the EXO70 (exocyst component of 70 kDa) subunit of the exocyst complex, resulting in inhibition of exocytosis and endosomal recycling in both plant and human cells and enhancement of plant vacuolar trafficking. An EXO70 protein with a C-terminal truncation results in dominant ES2 resistance, uncovering possible distinct regulatory roles for the N terminus of the protein. This study not only provides a valuable tool in studying exocytosis regulation but also offers a potentially new target for drugs aimed at addressing human disease.

The lncRNA CASC15 regulates SOX4 expression in RUNX1-rearranged acute leukemia.

BACKGROUND: Long non-coding RNAs (lncRNAs) play a variety of cellular roles, including regulation of transcription and translation, leading to alterations in gene expression. Some lncRNAs modulate the expression of chromosomally adjacent genes. Here, we assess the roles of the lncRNA CASC15 in regulation of a chromosomally nearby gene, SOX4, and its function in RUNX1/AML translocated leukemia. RESULTS: CASC15 is a conserved lncRNA that was upregulated in pediatric B-acute lymphoblastic leukemia (B-ALL) with t (12; 21) as well as pediatric acute myeloid leukemia (AML) with t (8; 21), both of which are associated with relatively better prognosis. Enforced expression of CASC15 led to a myeloid bias in development, and overall, decreased engraftment and colony formation. At the cellular level, CASC15 regulated cellular survival, proliferation, and the expression of its chromosomally adjacent gene, SOX4. Differentially regulated genes following CASC15 knockdown were enriched for predicted transcriptional targets of the Yin and Yang-1 (YY1) transcription factor. Interestingly, we found that CASC15 enhances YY1-mediated regulation of the SOX4 promoter. CONCLUSIONS: Our findings represent the first characterization of this CASC15 in RUNX1-translocated leukemia, and point towards a mechanistic basis for its action.

Nanotechnology to augment immunotherapy for the treatment of glioblastoma multiforme.

Glioblastoma multiforme (GBM) is characterized as one of the most common and most deadly malignant primary brain tumors. Current treatment modalities include the use of surgical resection and adjuvant chemotherapy and radiation therapy, though survival is still limited. Because of this, new treatment strategies are needed to improve overall survival. Immunotherapy has emerged as a potential treatment, but still possesses certain limitations to have a substantial clinical effect. In addition, nanotechnology has emerged as potent treatment effectors that have been shown to augment the effects of therapies including chemotherapy, gene therapy, and more. Nanoparticles possess a novel approach due to the myriad of functional groups that can create targeted treatments, though further optimization is still required. In this review, the authors will present the current uses and abilities of nanotechnology and its implication for use with immunotherapy in the treatment of GBM.

A novel thin plate spline methodology to model tissue surfaces and quantify tumor cell invasion in organ-on-chip models.

Organ-on-chip (OOC) models can be useful tools for cancer drug discovery. Advances in OOC technology have led to the development of more complex assays, yet analysis of these systems does not always account for these advancements, resulting in technical challenges. A challenging task in the analysis of these two-channel microfluidic models is to define the boundary between the channels so objects moving within and between channels can be quantified. We propose a novel imaging-based application of a thin plate spline method - a generalized cubic spline that can be used to model coordinate transformations - to model a tissue boundary and define compartments for quantification of invaded objects, representing the early steps in cancer metastasis. To evaluate its performance, we applied our analytical approach to an adapted OOC developed by Emulate, Inc., utilizing a two-channel system with endothelial cells in the bottom channel and colorectal cancer (CRC) patient-derived organoids (PDOs) in the top channel. Initial application and visualization of this method revealed boundary variations due to microscope stage tilt and ridge and valley-like contours in the endothelial tissue surface. The method was functionalized into a reproducible analytical process and web tool - the Chip Invasion and Contour Analysis (ChICA) - to model the endothelial surface and quantify invading tumor cells across multiple chips. To illustrate applicability of the analytical method, we applied the tool to CRC organoid-chips seeded with two different endothelial cell types and measured distinct variations in endothelial surfaces and tumor cell invasion dynamics. Since ChICA utilizes only positional data output from imaging software, the method is applicable to and agnostic of the imaging tool and image analysis system used. The novel thin plate spline method developed in ChICA can account for variation introduced in OOC manufacturing or during the experimental workflow, can quickly and accurately measure tumor cell invasion, and can be used to explore biological mechanisms in drug discovery.

A novel thin plate spline methodology to model tissue surfaces and quantify tumor cell invasion in organ-on-chip models.

Organ-on-chip (OOC) models can be useful tools for cancer drug discovery. Advances in OOC technology have led to the development of more complex assays, yet analysis of these systems does not always account for these advancements, resulting in technical challenges. A challenging task in the analysis of these two-channel microfluidic models is to define the boundary between the channels so objects moving within and between channels can be quantified. We propose a novel imaging-based application of a thin plate spline method - a generalized cubic spline that can be used to model coordinate transformations - to model a tissue boundary and define compartments for quantification of invaded objects, representing the early steps in cancer metastasis. To evaluate its performance, we applied our analytical approach to an adapted OOC developed by Emulate, Inc., utilizing a two-channel system with endothelial cells in the bottom channel and colorectal cancer (CRC) patient-derived organoids (PDOs) in the top channel. Initial application and visualization of this method revealed boundary variations due to microscope stage tilt and ridge and valley-like contours in the endothelial tissue surface. The method was functionalized into a reproducible analytical process and web tool - the Chip Invasion and Contour Analysis (ChICA) - to model the endothelial surface and quantify invading tumor cells across multiple chips. To illustrate applicability of the analytical method, we applied the tool to CRC organoid-chips seeded with two different endothelial cell types and measured distinct variations in endothelial surfaces and tumor cell invasion dynamics. Since ChICA utilizes only positional data output from imaging software, the method is applicable to and agnostic of the imaging tool and image analysis system used. The novel thin plate spline method developed in ChICA can account for variation introduced in OOC manufacturing or during the experimental workflow, can quickly and accurately measure tumor cell invasion, and can be used to explore biological mechanisms in drug discovery.

Immune biomarkers associated with COVID-19 disease severity in an urban, hospitalized population.

Objectives: We sought to identify immune biomarkers associated with severe Coronavirus disease 2019 (COVID-19) in patients admitted to a large urban hospital during the early phase of the SARS-CoV-2 pandemic. Design: The study population consisted of SARS-CoV-2 positive subjects admitted for COVID-19 (n = 58) or controls (n = 14) at the Los Angeles County University of Southern California Medical Center between April 2020 through December 2020. Immunologic markers including chemokine/cytokines (IL-6, IL-8, IL-10, IP-10, MCP-1, TNF-α) and serologic markers against SARS-CoV-2 antigens (including spike subunits S1 and S2, receptor binding domain, and nucleocapsid) were assessed in serum collected on the day of admission using bead-based multiplex immunoassay panels. Results: We observed that body mass index (BMI) and SARS-CoV-2 antibodies were significantly elevated in patients with the highest COVID-19 disease severity. IP-10 was significantly elevated in COVID-19 patients and was associated with increased SARS-CoV-2 antibodies. Interactions among all available variables on COVID-19 disease severity were explored using a linear support vector machine model which supported the importance of BMI and SARS-CoV-2 antibodies. Conclusions: Our results confirm the known adverse association of BMI on COVID-19 severity and suggest that IP-10 and SARS-CoV-2 antibodies could be useful to identify patients most likely to experience the most severe forms of the disease.

The role of PENNYWISE and POUND-FOOLISH in the maintenance of the shoot apical meristem in Arabidopsis.

Growth of the aerial part of the plant is dependent upon the maintenance of the shoot apical meristem (SAM). A balance between the self-renewing stem cells in the central zone (CZ) and organogenesis in the peripheral zone (PZ) is essential for the integrity, function, and maintenance of the SAM. Understanding how the SAM maintains a balance between stem cell perpetuation and organogenesis is a central question in plant biology. Two related BELL1-like homeodomain proteins, PENNYWISE (PNY) and POUND-FOOLISH (PNF), act to specify floral meristems during reproductive development. However, genetic studies also show that PNY and PNF regulate the maintenance of the SAM. To understand the role of PNY and PNF in meristem maintenance, the expression patterns for genes that specifically localize to the peripheral and central regions of the SAM were examined in Arabidopsis (Arabidopsis thaliana). Results from these experiments indicate that the integrity of the CZ is impaired in pny pnf plants, which alters the balance of stem cell renewal and organogenesis. As a result, pools of CZ cells may be allocated into initiating leaf primordia. Consistent with these results, the integrity of the central region of pny pnf SAMs can be partially restored by increasing the size of the CZ. Interestingly, flower specification is also reestablished by augmenting the size of the SAM in pny pnf plants. Taken together, we propose that PNY and PNF act to restrict organogenesis to the PZ by maintaining a boundary between the CZ and PZ.

Adaptation of Imaging Mass Cytometry to Explore the Single Cell Alloimmune Landscape of Liver Transplant Rejection.

Rejection continues to be an important cause of graft loss in solid organ transplantation, but deep exploration of intragraft alloimmunity has been limited by the scarcity of clinical biopsy specimens. Emerging single cell immunoprofiling technologies have shown promise in discerning mechanisms of autoimmunity and cancer immunobiology. Within these applications, Imaging Mass Cytometry (IMC) has been shown to enable highly multiplexed, single cell analysis of immune phenotypes within fixed tissue specimens. In this study, an IMC panel of 10 validated markers was developed to explore the feasibility of IMC in characterizing the immune landscape of chronic rejection (CR) in clinical tissue samples obtained from liver transplant recipients. IMC staining was highly specific and comparable to traditional immunohistochemistry. A single cell segmentation analysis pipeline was developed that enabled detailed visualization and quantification of 109,245 discrete cells, including 30,646 immune cells. Dimensionality reduction identified 11 unique immune subpopulations in CR specimens. Most immune subpopulations were increased and spatially related in CR, including two populations of CD45+/CD3+/CD8+ cytotoxic T-cells and a discrete CD68+ macrophage population, which were not observed in liver with no rejection (NR). Modeling via principal component analysis and logistic regression revealed that single cell data can be utilized to construct statistical models with high consistency (Wilcoxon Rank Sum test, p=0.000036). This study highlights the power of IMC to investigate the alloimmune microenvironment at a single cell resolution during clinical rejection episodes. Further validation of IMC has the potential to detect new biomarkers, identify therapeutic targets, and generate patient-specific predictive models of clinical outcomes in solid organ transplantation.

Specification of reproductive meristems requires the combined function of SHOOT MERISTEMLESS and floral integrators FLOWERING LOCUS T and FD during Arabidopsis inflorescence development.

In Arabidopsis floral meristems are specified on the periphery of the inflorescence meristem by the combined activities of the FLOWERING LOCUS T (FT)-FD complex and the flower meristem identity gene LEAFY. The floral specification activity of FT is dependent upon two related BELL1-like homeobox (BLH) genes PENNYWISE (PNY) and POUND-FOOLISH (PNF) which are required for floral evocation. PNY and PNF interact with a subset of KNOTTED1-LIKE homeobox proteins including SHOOT MERISTEMLESS (STM). Genetic analyses show that these BLH proteins function with STM to specify flowers and internodes during inflorescence development. In this study, experimental evidence demonstrates that the specification of flower and coflorescence meristems requires the combined activities of FT-FD and STM. FT and FD also regulate meristem maintenance during inflorescence development. In plants with reduced STM function, ectopic FT and FD promote the formation of axillary meristems during inflorescence development. Lastly, gene expression studies indicate that STM functions with FT-FD and AGAMOUS-LIKE 24 (AGL24)-SUPPRESSOR OF OVEREXPRESSION OF CONTANS1 (SOC1) complexes to up-regulate flower meristem identity genes during inflorescence development.

Creation of a Single Cell RNASeq Meta-Atlas to Define Human Liver Immune Homeostasis.

The liver is unique in both its ability to maintain immune homeostasis and in its potential for immune tolerance following solid organ transplantation. Single-cell RNA sequencing (scRNA seq) is a powerful approach to generate highly dimensional transcriptome data to understand cellular phenotypes. However, when scRNA data is produced by different groups, with different data models, different standards, and samples processed in different ways, it can be challenging to draw meaningful conclusions from the aggregated data. The goal of this study was to establish a method to combine 'human liver' scRNA seq datasets by 1) characterizing the heterogeneity between studies and 2) using the meta-atlas to define the dominant phenotypes across immune cell subpopulations in healthy human liver. Publicly available scRNA seq data generated from liver samples obtained from a combined total of 17 patients and ~32,000 cells were analyzed. Liver-specific immune cells (CD45+) were extracted from each dataset, and immune cell subpopulations (myeloid cells, NK and T cells, plasma cells, and B cells) were examined using dimensionality reduction (UMAP), differential gene expression, and ingenuity pathway analysis. All datasets co-clustered, but cell proportions differed between studies. Gene expression correlation demonstrated similarity across all studies, and canonical pathways that differed between datasets were related to cell stress and oxidative phosphorylation rather than immune-related function. Next, a meta-atlas was generated via data integration and compared against PBMC data to define gene signatures for each hepatic immune subpopulation. This analysis defined key features of hepatic immune homeostasis, with decreased expression across immunologic pathways and enhancement of pathways involved with cell death. This method for meta-analysis of scRNA seq data provides a novel approach to broadly define the features of human liver immune homeostasis. Specific pathways and cellular phenotypes described in this human liver immune meta-atlas provide a critical reference point for further study of immune mediated disease processes within the liver.

Human colorectal cancer-on-chip model to study the microenvironmental influence on early metastatic spread.

Colorectal cancer (CRC) progression is a complex process that is not well understood. We describe an in vitro organ-on-chip model that emulates in vivo tissue structure and the tumor microenvironment (TME) to better understand intravasation, an early step in metastasis. The CRC-on-chip incorporates fluid flow and peristalsis-like cyclic stretching and consists of endothelial and epithelial compartments, separated by a porous membrane. On-chip imaging and effluent analyses are used to interrogate CRC progression and the resulting cellular heterogeneity. Mass spectrometry-based metabolite profiles are indicative of a CRC disease state. Tumor cells intravasate from the epithelial channel to the endothelial channel, revealing differences in invasion between aggressive and non-aggressive tumor cells. Tuning the TME by peristalsis-like mechanical forces, the epithelial:endothelial interface, and the addition of fibroblasts influences the invasive capabilities of tumor cells. The CRC-on-chip is a tunable human-relevant model system and a valuable tool to study early invasive events in cancer.

Accuracy and outcomes of diffusion tensor imaging tractography in resection for vestibular schwannoma for facial nerve preservation.

BACKGROUND: Impairment of facial nerve (FN) function is a common postoperative complication in surgical resections of Vestibular Schwannomas (VS). Diffusion tensor imaging (DTI) tractography creates in vivo imaging of the anatomical location of white matter tracts that can be preoperatively used to visualize the displaced FN. We present an analysis of patients who underwent DTI tractography imaging prior to VS resection. METHODS: Patient charts were reviewed from March 2012 to April 2015 who underwent DTI tractography prior to surgical resection for VS. Reliability of this measure was compared to the intraoperative FN location as determined by the surgeon. House Brackmann (HB) score was used to assess facial nerve function. RESULTS: A total of 11 patients were included with a mean age of 43 years (range: 19-64) and mean follow-up length of 11.9 months (range: 3.1-34.2). The average maximum tumor diameter was 2.82 cm (range: 1.7-4.2). DTI tractography was accurate in 90.9% (10/11) of patients. Postoperatively, 72.7% (8/11) had a HB score of I or II, 18.2% (2/11) had a HB score of III, and 9.1% (1/11) had a HB score of IV. CONCLUSIONS: Facial nerve visualization for VS resection can be accurately visualized using DTI tractography. This modality may lead to reduction of postoperative FN damage.

Imaging-Based Machine Learning Analysis of Patient-Derived Tumor Organoid Drug Response.

Three-quarters of compounds that enter clinical trials fail to make it to market due to safety or efficacy concerns. This statistic strongly suggests a need for better screening methods that result in improved translatability of compounds during the preclinical testing period. Patient-derived organoids have been touted as a promising 3D preclinical model system to impact the drug discovery pipeline, particularly in oncology. However, assessing drug efficacy in such models poses its own set of challenges, and traditional cell viability readouts fail to leverage some of the advantages that the organoid systems provide. Consequently, phenotypically evaluating complex 3D cell culture models remains difficult due to intra- and inter-patient organoid size differences, cellular heterogeneities, and temporal response dynamics. Here, we present an image-based high-content assay that provides object level information on 3D patient-derived tumor organoids without the need for vital dyes. Leveraging computer vision, we segment and define organoids as independent regions of interest and obtain morphometric and textural information per organoid. By acquiring brightfield images at different timepoints in a robust, non-destructive manner, we can track the dynamic response of individual organoids to various drugs. Furthermore, to simplify the analysis of the resulting large, complex data files, we developed a web-based data visualization tool, the Organoizer, that is available for public use. Our work demonstrates the feasibility and utility of using imaging, computer vision and machine learning to determine the vital status of individual patient-derived organoids without relying upon vital dyes, thus taking advantage of the characteristics offered by this preclinical model system.

Comparison of Cell and Organoid-Level Analysis of Patient-Derived 3D Organoids to Evaluate Tumor Cell Growth Dynamics and Drug Response.

3D cell culture models have been developed to better mimic the physiological environments that exist in human diseases. As such, these models are advantageous over traditional 2D cultures for screening drug compounds. However, the practicalities of transitioning from 2D to 3D drug treatment studies pose challenges with respect to analysis methods. Patient-derived tumor organoids (PDTOs) possess unique features given their heterogeneity in size, shape, and growth patterns. A detailed assessment of the length scale at which PDTOs should be evaluated (i.e., individual cell or organoid-level analysis) has not been done to our knowledge. Therefore, using dynamic confocal live cell imaging and data analysis methods we examined tumor cell growth rates and drug response behaviors in colorectal cancer (CRC) PDTOs. High-resolution imaging of H2B-GFP-labeled organoids with DRAQ7 vital dye permitted tracking of cellular changes, such as cell birth and death events, in individual organoids. From these same images, we measured morphological features of the 3D objects, including volume, sphericity, and ellipticity. Sphericity and ellipticity were used to evaluate intra- and interpatient tumor organoid heterogeneity. We found a strong correlation between organoid live cell number and volume. Linear growth rate calculations based on volume or live cell counts were used to determine differential responses to therapeutic interventions. We showed that this approach can detect different types of drug effects (cytotoxic vs cytostatic) in PDTO cultures. Overall, our imaging-based quantification workflow results in multiple parameters that can provide patient- and drug-specific information for screening applications.

mTORC2 contributes to the metabolic reprogramming in EGFR tyrosine-kinase inhibitor resistant cells in non-small cell lung cancer.

Non-small cell lung cancer (NSCLC) patients with activating EGFR mutations are often successfully treated with EGFR tyrosine kinase inhibitor (TKI) such as erlotinib; however, treatment resistance inevitably occurs. Given tumor metabolism of glucose and therapeutic response are intimately linked, we explored the metabolic differences between isogenic erlotinib-sensitive and -resistant NSCLC cell lines. We discovered that the growth of erlotinib-resistant cells is more sensitive to glucose deprivation. Seahorse metabolic assay revealed erlotinib-resistant cells have lower spare respiratory capacity (SRC), an indicator of metabolic flexibility, compared to erlotinib-sensitive cells. Additionally, we found downstream components of mTORC2 signaling to be phosphorylated in erlotinib-resistant cells. Knockdown of an mTORC2 component, Rictor, enhanced the SRC and rescued the growth rate of erlotinib-resistant cells during glucose deprivation. Among NSCLCs with activating EGFR mutations, gene sets involved in glucose metabolism were enriched in patients with high expression of p-NDGR1, a readout of mTORC2 activity. Furthermore, overall survival was negatively correlated with p-NDRG1. Our work uncovers a link between mTORC2 and metabolic reprogramming in EGFR TKI-resistant cells and highlights the significance of mTORC2 in the progression of EGFR-mutated NSCLC.

Impact of Cochlear Dose on Hearing Preservation following Stereotactic Radiosurgery and Fractionated Stereotactic Radiotherapy for the Treatment of Vestibular Schwannoma.

Objective The objective of this study was to examine the effect of cochlear dose on hearing preservation in stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (fSRT) for vestibular schwannoma (VS). Design This is a retrospective case-control study. Setting This study was completed at the Ronald Reagan UCLA Medical Center, a university-affiliated tertiary care center. Participants Patients who underwent SRS (marginal dose of 12 Gy) or fSRT (marginal dose of 50.4 Gy) procedures for VS were included in the study. Main Outcome Measures The main outcome measure was hearing preservation. Audiometric data, when available, were used to determine the level of hearing according to the Gardner Robertson scale. Results A total of 38 patients (14 SRS and 24 fSRT) were analyzed. SRS patients with decreased hearing received a significantly higher minimum cochlear dose (7.41 vs. 4.24 Gy, p = 0.02) as compared with those with stable hearing. In fSRT patients, there were no significant differences in cochlear dose for patients with decreased hearing as compared with those with stable hearing. For SRS patients, who received a minimum cochlear dose above 6 Gy, there was a significant risk of decreased hearing preservation (odds ratio: 32, p = 0.02). Conclusion Higher minimum cochlear dose was predictive of decreased hearing preservation following SRS. Though the study is low powered, the radiation dose to the cochlea should be a parameter that is considered when planning SRS or fSRT therapies for patients with VS.

Minimally Invasive Middle Fossa Keyhole Craniectomy for Repair of Superior Semicircular Canal Dehiscence.

BACKGROUND: Superior semicircular canal dehiscence (SSCD) presents with varying degrees of auditory and vestibular dysfunction. The condition is confirmed on high-resolution computed tomography (CT) imaging, and symptoms are often improved by surgical repair. Although a classic middle fossa craniotomy has been used with good results, recent advances in technique have allowed for modification of the traditional approach into a smaller skin incision and a minimally invasive middle fossa keyhole craniectomy roughly 1.7 cm in diameter. OBJECTIVE: To delineate this novel approach and describe the technique for accurate localization of the dehiscence using preoperative measurements and intraoperative image guidance, thereby minimizing the need for a larger skin incision and craniotomy. METHODS: Patients were independently diagnosed with SSCD by the senior authors. Once relevant imaging was acquired, the novel keyhole technique was performed. Patients' vestibular and auditory symptoms before and after the procedure were assessed. Outcomes from a series of patients treated with this keyhole approach were tabulated and reported. RESULTS: Twelve cases from 11 patients were included in this series. Auditory symptoms had high rates of resolution with pulsatile tinnitus, internal amplification of sounds, and autophony being resolved in a majority of cases. Only 2 cases reported hearing decline. Sound/pressure induced vertigo and disequilibrium also demonstrated high rates of resolution. No complications were reported. CONCLUSION: The minimally invasive middle fossa keyhole craniectomy is a novel approach for the repair of SSCD. This approach may contribute to resolved auditory and vestibular symptoms with low morbidity and quick recovery.

Outcomes of middle fossa craniotomy for the repair of superior semicircular canal dehiscence.

Superior semicircular canal dehiscence (SSCD) is a rare defect of the arcuate eminence that causes an abnormal connection between the superior semicircular canal and middle cranial fossa. Patients often present with a variety of auditory and vestibular symptoms. Trigger avoidance is the initial strategy, but surgery may be necessary in debilitating cases. We retrospectively reviewed SSCD patients undergoing repair via a middle fossa craniotomy between March 2011 and September 2015. Forty-nine patients undergoing 58 surgeries were identified. Autophony was the most common symptom at presentation (n=44; 90%). Mean follow-up was 10.9months, with 100% of patients reporting resolution of at least one symptom. Aural fullness was the most commonly resolved symptom following surgical repair (n=19/22; 86%). Hearing loss (n=11/25; 44%) and tinnitus (n=11/38; 29%) were the most common symptoms to persist following surgery. The most common symptom to develop after surgery was disequilibrium (n=4/18; 22%). Upon comparing the overall pre-operative and post-operative groups, the number of patients with autophony (p<0.0001), aural fullness (p=0.0006), hearing loss (p=0.0119), disequilibrium (p=0.0002), sound- and pressure-induced vertigo (p<0.0001), and tinnitus (p<0.0001) were significantly different. Improved clinical outcomes were demonstrated in patients undergoing SSCD repair through a middle cranial fossa approach. The most common presenting symptom (autophony) was also most likely to resolve after surgery. Hearing loss is less amenable to surgical correction. Disequilibrium developed in a small number of patients after repair.