Faculty Bibliography

Purpose/Objective(s): Early stage supraglottic larynx cancers treated with definitive radiotherapy (RT) require treatment of the bilateral neck because of high rates of regional spread. Compared to older techniques, modern intensity modulated radiation therapy (IMRT) has been shown to precisely target tumor and draining nodal regions with the potential to spare organs at risk including those essential for prevention of aspiration. However, previous hospital-based studies have demonstrated decreased survival associated with the use of IMRT compared to 3D and 2D radiotherapy techniques in glottic larynx. We used the National Cancer Data Base (NC

Glioblastoma (GBM) stem cells (GSCs) reside in both hypoxic and vascular microenvironments within tumors. The molecular mechanisms that allow GSCs to occupy such contrasting niches are not understood. We used patient-derived GBM cultures to identify GSC subtypes with differential activation of Notch signaling, which co-exist in tumors but occupy distinct niches and match their metabolism accordingly. Multipotent GSCs with Notch pathway activation reside in perivascular niches, and are unable to entrain anaerobic glycolysis during hypoxia. In contrast, most CD133-expressing GSCs do not depend on canonical Notch signaling, populate tumors regardless of local vascularity and selectively utilize anaerobic glycolysis to expand in hypoxia. Ectopic activation of Notch signaling in CD133-expressing GSCs is sufficient to suppress anaerobic glycolysis and resistance to hypoxia. These findings demonstrate a novel role for Notch signaling in regulating GSC metabolism and suggest intratumoral GSC heterogeneity ensures metabolic adaptations to support tumor growth in diverse tumor microenvironments.

Within reflex circuits, specific anatomical projections allow central neurons to relay sensations to effectors that generate movements. A major challenge is to relate anatomical features of central neural populations -- such as asymmetric connectivity -- to the computations the populations perform. To address this problem, we mapped the anatomy, modeled the function, and discovered a new behavioral role for a genetically-defined population of central vestibular neurons in rhombomeres 5-7 of larval zebrafish. First, we found that neurons within this central population project preferentially to motoneurons that move the eyes downward. Concordantly, when the entire population of asymmetrically-projecting neurons was stimulated collectively, only downward eye rotations were observed, demonstrating a functional correlate of the anatomical bias. When these neurons are ablated, fish failed to rotate their eyes following either nose-up or nose-down body tilts. This asymmetrically-projecting central population thus participates in both up and downward gaze stabilization. In addition to projecting to motoneurons, central vestibular neurons also receive direct sensory input from peripheral afferents. To infer whether asymmetric projections can facilitate sensory encoding or motor output, we modeled differentially-projecting sets of central vestibular neurons. Whereas motor command strength was independent of projection allocation, asymmetric projections enabled more accurate representation of nose-up stimuli. The model shows how asymmetric connectivity could enhance the representation of imbalance during nose-up postures while preserving gaze-stabilization performance. Finally, we found that central vestibular neurons were necessary for a vital behavior requiring maintenance of a nose-up posture: swim bladder inflation. These observations suggest that asymmetric connectivity in the vestibular system facilitates representation of ethologically-relevant stimuli without compromising reflexive behavior.SIGNIFICANCE STATEMENTInterneuron populations use specific anatomical projections to transform sensations into reflexive actions. Here we examined how the anatomical composition of a genetically-defined population of balance interneurons in the larval zebrafish relates to the computations it performs. First, we found that the population of interneurons that stabilize gaze preferentially project to motoneurons that move the eyes downward. Next, we discovered through modeling that such projection patterns can enhance the encoding of nose-up sensations without compromising gaze stabilization. Finally we found that loss of these interneurons impairs a vital behavior, swim bladder inflation, that relies on maintaining a nose-up posture. These observations suggest that anatomical specialization permits neural circuits to represent relevant features of the environment without compromising behavior.

OBJECTIVE: To compare the intraoperative electrically evoked auditory brainstem response (EABR) morphologies between neurofibromatosis II (NF2) adult auditory brainstem implant (ABI) recipients who had auditory percepts post-operatively and those who did not and between NF2 adult ABI recipients and non-NF2 pediatric ABI recipients. METHODS: This was a retrospective case series at a single tertiary academic referral center examining all ABI recipients from 1994 to 2016, which included 34 NF2 adults and 11 non-NF2 children. The morphologies of intraoperative EABRs were evaluated for the number of waveforms showing a response, the number of positive peaks in those responses, and the latencies of each of these peaks. RESULTS: 27/34 adult NF2 patients and 9/10 children had EABR waveforms. 20/27 (74.0%) of the adult patients and all of the children had ABI devices that stimulated post-operatively. When comparing the waveforms between adults who stimulated and those who did not stimulate, the proportion of total number of intraoperative EABR peaks to total possible peaks was significantly higher for the adults who stimulated than for those who did not (p < 0.05). Children had a significantly higher proportion of total number of peaks to total possible peaks when compared to adults who stimulated (p < 0.02). Additionally, there were more likely to be EABR responses at the initial stimulation than intraoperatively in the pediatric ABI population (p = 0.065). CONCLUSIONS: The value of intraoperative EABR tracing may lie in its ability to predict post-operative auditory percepts based on the placement of the array providing the highest number of total peaks.

Due to its central location, the nose plays a prominent role in facial aesthetics. As tastes have shifted and techniques have advanced, the accepted "ideal" appearance and proportions of the nose have evolved over time. By assessing the aesthetics of the nasal dorsum through the use of lines and angles, one can more precisely elucidate a goal for the patient's postoperative nasal shape, which should, in turn, guide the surgeon to execute specific operative maneuvers needed to achieve that contour. In assessing the aesthetics of the nasal dorsum, practitioners calculate and observe aspects such as the paired dorsal aesthetic lines, the nasofrontal angle, and the nasofacial angle. There is also additional consideration given to nasal tip position as this must fit harmoniously with the shape of the dorsum. In contrast to the established aesthetic lines and angles, using nasal geometric polygons for the aesthetic evaluation and development of operative goals in rhinoplasty has recently been described in the literature. Constructed ideals, in the form of proportions, lines, and angles, should be used with caution, as there are many factors to consider in the aesthetic analysis of the nasal dorsum, including ethnic differences, and subjective and changing views of beauty.

PURPOSE OF REVIEW: To provide an overview of the treatment options for nonflaccid facial paralysis including physical rehabilitation, botulinum toxin injection and surgical intervention. To also describe recent technique advances regarding facial synkinesis in each zone of facial movement. RECENT FINDINGS: Physical therapy and neuromodulation with botulinum toxin continues to be the main treatment strategy for facial synkinesis. Treating the orbicularis oculi, mentalis and platysma muscles with neurotoxin has been well described. A symmetric smile can also be improved with ipsilateral depressor anguli oris and the contralateral depressor labi inferioris weakening. Novel surgical techniques to selectively ablate specific facial muscles have also been recently described. SUMMARY: Nonflaccid facial paralysis is a spectrum of hypokinetic and hyperkinetic movement following facial nerve injury that is best treated in a patient-tailored graduated fashion. Novel techniques are evolving to maximize patient function while minimizing morbidity.

Spontaneous hematoma within the iliopsoas muscle (SIH) is a rare complication most commonly seen in coagulopathic patients. Often, patients undergoing microvascular free tissue transfer are anticoagulated for anastomotic patency. Here we describe two cases of postoperative SIH following contralateral anterolateral thigh (ALT) free tissue transfer for reconstruction of oncologic head and neck defects. Both patients described hip pain after mobilization and had a corresponding acute blood loss anemia. Diagnosis of SIH was confirmed by CT and both patients were managed conservatively. Given that anticoagulation is a common practice following head and neck free tissue transfer, surgeons should be aware of this potential complication.

Long-term modifications of neuronal connections are critical for reliable memory storage in the brain. However, their locus of expression-pre- or postsynaptic-is highly variable. Here we introduce a theoretical framework in which long-term plasticity performs an optimization of the postsynaptic response statistics toward a given mean with minimal variance. Consequently, the state of the synapse at the time of plasticity induction determines the ratio of pre- and postsynaptic modifications. Our theory explains the experimentally observed expression loci of the hippocampal and neocortical synaptic potentiation studies we examined. Moreover, the theory predicts presynaptic expression of long-term depression, consistent with experimental observations. At inhibitory synapses, the theory suggests a statistically efficient excitatory-inhibitory balance in which changes in inhibitory postsynaptic response statistics specifically target the mean excitation. Our results provide a unifying theory for understanding the expression mechanisms and functions of long-term synaptic transmission plasticity.