Ten-Year Experience of Chest Wall Reconstruction: Retrospective Review of a Titanium Plate MatrixRIB™ System.

Chest wall tumor resection can result in a large defect that can pose a challenge in reconstruction in restoring chest wall contour, maintaining respiratory mechanics, and improving cosmesis. Titanium plates were first introduced for treating a traumatic flail chest, which yielded promising results in restoring chest wall stability. Subsequently, the applications of titanium plates in chest wall reconstruction surgery were demonstrated in case reports and series. Our center has adopted this technique for a decade, and patients are actively followed up after operation. Here, we retrospectively analyze our 10-year experience of using titanium plates and other reconstruction approaches for chest wall reconstruction, in terms of clinical outcomes, complications, and reasons for reoperation to determine long-term safety and efficacy. Thirty-eight patients who underwent chest wall resection and reconstruction surgery were identified. Of these, 11 had titanium plate insertion, 11 had patch repair or flap reconstruction, and the remaining 16 had primary closure of defects. Chest wall reconstruction using titanium plate(s) and patch repair (with or without flap reconstruction) was associated with larger chest wall defects and more sternal resections than primary closure. Subgroup analysis also showed that reconstruction by the titanium plate technique was associated with larger chest wall defects than patch repair or flap reconstruction [286.80 cm2 vs. 140.91 cm2 (p = 0.083)]. There was no 30-day hospital mortality. Post-operative arrhythmia was more commonly seen following chest wall reconstruction compared with primary closure (p = 0.041). Furthermore, more wound infections were detected following the use of titanium plate reconstruction compared with the patch repair (with or without flap reconstruction) approach (p = 0.027). In conclusion, the titanium plate system is a safe, effective, and robust approach for chest wall reconstruction surgery, especially in tackling larger defect sizes.

Responses of midbrain auditory neurons to two different environmental sounds-A new approach on cross-sound modeling.

When modeling auditory responses to environmental sounds, results are satisfactory if both training and testing are restricted to datasets of one type of sound. To predict 'cross-sound' responses (i.e., to predict the response to one type of sound e.g., rat Eating sound, after training with another type of sound e.g., rat Drinking sound), performance is typically poor. Here we implemented a novel approach to improve such cross-sound modeling (single unit datasets were collected at the auditory midbrain of anesthetized rats). The method had two key features: (a) population responses (e.g., average of 32 units) instead of responses of individual units were analyzed; and (b) the long sound segment was first divided into short segments (single sound-bouts), their similarity was then computed over a new metric involving the response (called Stimulus Response Model map or SRM map), and finally similar sound-bouts (regardless of sound type) and their associated responses (peri-stimulus time histograms, PSTHs) were modelled. Specifically, a committee machine model (artificial neural networks with 20 stratified spectral inputs) was trained with datasets from one sound type before predicting PSTH responses to another sound type. Model performance was markedly improved up to 92%. Results also suggested the involvement of different neural mechanisms in generating the early and late responses to amplitude transients in the broad-band environmental sounds. We concluded that it is possible to perform rather satisfactory cross-sound modeling on datasets grouped together based on their similarities in terms of the new metric of SRM map.

Evaluating Instantaneous Perfusion Responses of Parotid Glands to Gustatory Stimulation Using High-Temporal-Resolution Echo-Planar Diffusion-Weighted Imaging.

BACKGROUND AND PURPOSE: Parotid glands secrete and empty saliva into the oral cavity rapidly after gustatory stimulation. However, the role of the temporal resolution of DWI in investigating parotid gland function remains uncertain. Our aim was to design a high-temporal-resolution echo-planar DWI pulse sequence and to evaluate the instantaneous MR perfusion responses of the parotid glands to gustatory stimulation. MATERIALS AND METHODS: This prospective study enrolled 21 healthy volunteers (M/F = 2:1; mean age, 45.2 ± 12.9 years). All participants underwent echo-planar DWI (total scan time, 304 seconds; temporal resolution, 4 s/scan) on a 1.5T MR imaging scanner. T2WI (b = 0 s/mm2) and DWI (b = 200 s/mm2) were qualitatively assessed. Signal intensity of the parotid glands on T2WI, DWI, and ADC was quantitatively analyzed. One-way ANOVA with post hoc group comparisons with Bonferroni correction was used for statistical analysis. P < .05 was statistically significant. RESULTS: Almost perfect interobserver agreement was achieved (κ ≥ 0.656). The parotid glands had magnetic susceptibility artifacts in 14.3% (3 of 21) of volunteers during swallowing on DWI but were free from perceptible artifacts at the baseline and at the end of scans on all images. Increased ADC and reduced signal intensity of the parotid glands on T2WI and DWI occurred immediately after oral administration of lemon juice. Maximal signal change of ADC (24.8% ± 10.8%) was significantly higher than that of T2WI (-10.1% ± 5.2%, P < .001). The recovery ratio of ADC (100.71% ± 42.34%) was also significantly higher than that of T2WI (22.36% ± 15.54%, P < .001). CONCLUSIONS: Instantaneous parotid perfusion responses to gustatory stimulation can be quantified by ADC by using high-temporal-resolution echo-planar DWI.

Importance of clothing removal in scalds.

OBJECTIVE: To test the hypothesis that prompt removal of clothing after scalds lessens the severity of injury. METHODS: This experimental study and case series was carried out in the Burn Centre of a tertiary hospital in Hong Kong. An experimental burn model using Allevyn (Smith & Nephew Medical Limited, Hull, England) as a skin substitute was designed to test the effect of delayed clothing removal on skin temperature using hot water and congee. Data of patients admitted with scalding by congee over a 10-year period (January 2005 to December 2014) were also studied. RESULTS: A significant reduction in the temperature of the skin model following a hot water scald was detected only if clothing was removed within the first 10 seconds of injury. With congee scalds, the temperature of the skin model progressively increased with further delay in clothing removal. During the study period, 35 patients were admitted with congee scalds to our unit via the emergency department. The majority were children. Definite conclusions supporting the importance of clothing removal could not be drawn due to our small sample size. Nonetheless, our data suggest that appropriate prehospital burn management can reduce patient morbidity. CONCLUSIONS: Prompt removal of clothing after scalding by congee may reduce post-burn morbidity.

Management of secondary lymphoedema.

Lymphoedema is a chronic, progressive condition. There is no cure but it is most easily managed with early recognition and therapy; those who do not have treatment tend to worsen rapidly and advanced disease is more difficult to treat than early disease. Surgery for lymphoedema is often regarded as a last resort but traditional excisional techniques that have been slightly modified for modern practice have shown good results, whilst newer microsurgical reconstruction techniques show promise although long-term results are lacking. This report provides an update on the therapy of lymphoedema.

Prolonged sound exposure has different effects on increasing neuronal size in the auditory cortex and brainstem.

Tone at moderate levels presented to young rats at a stage (postnatal week-4) presumably that has passed the cortical critical period still can enlarge neurons in the auditory cortex. It remains unclear whether this delayed plastic change occurs only in the cortex, or reflects a change taking place in the auditory brainstem. Here we compared sound-exposure effects on neuronal size in the auditory cortex and the midbrain. Starting from postnatal day 22, young rats were exposed to a low-frequency tone (4 kHz at 65 dB SPL) for a period of 3 (postnatal day 22-25) or 7 (postnatal day 22-29) days before sacrifice. Neurons were analyzed morphometrically from 7 µm-thick histological sections. A marked increase in neuronal size (32%) was found at the cortex in the high-frequency region distant from the exposing tone. The increase in the midbrain was even larger (67%) and was found in both the low and high frequency regions. While cell enlargements were clear at day 29, only in the high frequency region of the cortex a slight enlargement was found at day 22, suggesting that the cortical and subcortical changes are synchronized, if not slightly preceded by the cortex. In contrast, no changes in neuronal size were found in the cochlear nucleus or the visual midbrain. Such differential effects of sound-exposure at the auditory centers across cortical and subcortical levels cannot be explained by a simple activity-driven change occurring earlier in the brainstem, and might involve function of other structures as for example the descending auditory system.

Double free flaps for reconstruction of complex/composite defects in head and neck surgery.

OBJECTIVE. To demonstrate the feasibility of double free flap surgery in head and neck reconstruction. DESIGN. Descriptive case series. SETTING. A university-affiliated hospital in Hong Kong. PATIENTS. Twelve patients with head and neck cancer (encountered over a 2.5-year period) who had reconstructive surgery with planned simultaneous double free flaps. RESULTS. The mean total operating time was 660 minutes and there were no flap failures. Postoperative stays ranged from 11 to 82 days; nine patients were discharged within 3 weeks and seven were able to maintain their weight with oral feeding. The survival rate up to 1 year was 64%. CONCLUSION. The use of double free flaps is an option worth considering for complex head and neck defects in carefully selected patients.

Modeling complex responses of FM-sensitive cells in the auditory midbrain using a committee machine.

Frequency modulation (FM) is an important building block of complex sounds that include speech signals. Exploring the neural mechanisms of FM coding with computer modeling could help understand how speech sounds are processed in the brain. Here, we modeled the single unit responses of auditory neurons recorded from the midbrain of anesthetized rats. These neurons displayed spectral temporal receptive fields (STRFs) that had multiple-trigger features, and were more complex than those with single-trigger features. Their responses have not been modeled satisfactorily with simple artificial neural networks, unlike neurons with simple-trigger features. To improve model performance, here we tested an approach with the committee machine. For a given neuron, the peri-stimulus time histogram (PSTH) was first generated in response to a repeated random FM tone, and peaks in the PSTH were segregated into groups based on the similarity of their pre-spike FM trigger features. Each group was then modeled using an artificial neural network with simple architecture, and, when necessary, by increasing the number of neurons in the hidden layer. After initial training, the artificial neural networks with their optimized weighting coefficients were pooled into a committee machine for training. Finally, the model performance was tested by prediction of the response of the same cell to a novel FM tone. The results showed improvement over simple artificial neural networks, supporting that trigger-feature-based modeling can be extended to cells with complex responses. This article is part of a Special Issue entitled Neural Coding 2012. This article is part of a Special Issue entitled Neural Coding 2012.

Analgesic effects of preoperative gabapentin after tongue reconstruction with the anterolateral thigh flap.

OBJECTIVE: To investigate gabapentin's role in head and neck cancer surgery following the demonstration of the effectiveness of gabapentin in reducing postoperative pain. DESIGN: Non-randomised open-label trial. SETTING: Prince of Wales Hospital, Hong Kong. MAIN OUTCOME MEASURES: Pain scores, analgesic usage, and the frequency of adverse effects. PATIENTS: In patients undergoing anterolateral thigh flap reconstruction after resection of tongue carcinoma, those who had an oral dose of gabapentin before surgery were compared to those who did not. RESULTS: Postoperative pain was reduced in the gabapentin group (1.2) compared to the control group (1.7) [P=0.05]. In the gabapentin group, mean morphine (patient-controlled analgesia) use (3.5 mg), sedation scores (1.0), and antiemetic usage (0 mg metoclopramide) were all significantly reduced in comparison to the controls with respective figures of 11.4 mg, 1.6, and 12.2 mg. CONCLUSION: Single preoperative doses of gabapentin led to significant reductions in postoperative pain and nausea with reduced analgesic and antiemetic usage, without additional side-effects or increases in operative complications.

Modeling frequency modulated responses of midbrain auditory neurons based on trigger features and artificial neural networks.

Frequency modulation (FM) is an important building block of communication signals for animals and human. Attempts to predict the response of central neurons to FM sounds have not been very successful, though achieving successful results could bring insights regarding the underlying neural mechanisms. Here we proposed a new method to predict responses of FM-sensitive neurons in the auditory midbrain. First we recorded single unit responses in anesthetized rats using a random FM tone to construct their spectro-temporal receptive fields (STRFs). Training of neurons in the artificial neural network to respond to a second random FM tone was based on the temporal information derived from the STRF. Specifically, the time window covered by the presumed trigger feature and its delay time to spike occurrence were used to train a finite impulse response neural network (FIRNN) to respond to this random FM. Finally we tested the model performance in predicting the response to another similar FM stimuli (third random FM tone). We found good performance in predicting the time of responses if not also the response magnitudes. Furthermore, the weighting function of the FIRNN showed temporal 'bumps' suggesting temporal integration of synaptic inputs from different frequency laminae. This article is part of a Special Issue entitled: Neural Coding.

Pressure injection demonstrates points of weakness in the posterior nasal arteries.

OBJECTIVE: To test the hypothesis that potential sites of weakness within normal nasal arteries, when stressed, contribute to the mechanism of epistaxis, we 'stress-tested' nasal arteries in unfixed cadaveric heads, using pressure injection of feeding arteries. MATERIALS AND METHODS: Indian ink with latex was injected into maxillary arteries under high pressure (620 mmHg). Stepwise dissection was carried out and areas showing ink leakage were examined. Control heads were injected at standard embalming pressures (375 mmHg). RESULTS: Ink leakage was found in all heads injected at higher pressure, and was restricted to the nasal mucosa. Histological examination of leakage points demonstrated vessel disruption consistent with dissecting aneurysm formation. DISCUSSION: Results showed that high pressure injection caused leakage from arteries in the posterior nose; the distribution of leakage points was consistent with many clinical investigations. The lesions produced were comparable with our best histopathological model of epistaxis, i.e. dissecting aneurysm formation. This suggests that pre-existing weaknesses in the arterial configuration may exist.

Fine frequency-modulation trigger features of midbrain auditory neurons extracted by the progressive thresholding method--a preliminary study.

Spectro-temporal receptive fields (STRFs) are commonly used to characterize response properties of central auditory neurons and for visualizing 'trigger features'. However, trigger features in STRF maps typically have a blurry appearance. Therefore it is unclear what details could be embedded in them. To investigate this, we developed a new method called 'progressive thresholding' to resolve fine structures in the STRFs, and applied the method to FM responses recorded from single units at the auditory midbrain of anesthetized rats. Random FM tones of a narrow frequency range (approximately 0.5 octave) were first presented to evoked spike responses at the cell's best frequency. Perispike modulating time waveforms collected (50 msec long, n = 1500 to 4000 tracings) were used to generate STRF based on spike-triggered-averaging. After supra-threshold areas of pixel counts had been determined through a step of progressive thresholding in the map, those peri-spike modulating waveforms passing through each area were dejittered systematically. At what seemed to be an optimal threshold, multiple trigger features (up to a maximum of 4 fine bands) were extracted from the initially simple-looking STRF. Results show that fine FM trigger features are present in STRFs and that they can be resolved with the present method of analysis.

Should spikes be treated with equal weightings in the generation of spectro-temporal receptive fields?

Knowledge on the trigger features of central auditory neurons is important in the understanding of speech processing. Spectro-temporal receptive fields (STRFs) obtained using random stimuli and spike-triggered averaging allow visualization of trigger features which often appear blurry in the time-versus-frequency plot. For a clearer visualization we have previously developed a dejittering algorithm to sharpen trigger features in the STRF of FM-sensitive cells. Here we extended this algorithm to segregate spikes, based on their dejitter values, into two groups: normal and outlying, and to construct their STRF separately. We found that while the STRF of the normal jitter group resembled full trigger feature in the original STRF, those of the outlying jitter group resembled a different or partial trigger feature. This algorithm allowed the extraction of other weaker trigger features. Due to the presence of different trigger features in a given cell, we proposed that in the generation of STRF, the evoked spikes should not be treated indiscriminately with equal weightings.

Epithelioid haemangioendothelioma of the anterior skull base: what is the optimal treatment?

We report an unusual malignant tumour affecting an unusual site. Epithelioid haemangioendothelioma was formerly considered a tumour of intermediate malignancy but has been reclassified as fully malignant. It is important to be aware of this clinical entity as the best hope of cure is timely radical resection. There is a paucity of evidence concerning the efficacy of alternative treatments because the tumour is very rare.

Convergence of the chiral expansion in two-flavor lattice QCD.

We test the convergence property of the chiral perturbation theory using a lattice QCD calculation of pion mass and decay constant with two dynamical quark flavors. The lattice calculation is performed using the overlap fermion formulation, which realizes exact chiral symmetry at finite lattice spacing. By comparing various expansion prescriptions, we find that the chiral expansion is well saturated at the next-to-leading order for pions lighter than approximately 450 MeV. Better convergence behavior is found, in particular, for a resummed expansion parameter xi, with which the lattice data in the pion mass region 290-750 MeV can be fitted well with the next-to-next-to-leading order formulas. We obtain the results in two-flavor QCD for the low energy constants l[over ]_{3} and l[over ]_{4} as well as the pion decay constant, the chiral condensate, and the average up and down quark mass.