Surgical complications of decompressive craniectomy in patients with head injury.

INTRODUCTION: Decompressive craniectomy is an important method for managing refractory intracranial hypertension. Although decompressive craniectomy is a relatively simple procedure, various complications may arise. The aim of our paper was to determine the incidence of complications of decompressive craniectomy in patients with head injury and to analyse their risk factors. METHODS: We retrospectively analysed a group of 94 patients after decompressive craniectomy for head injury between 01 Jan 2014 and 31 Dec 2018. Postoperative complications were evaluated based on clinical examination and postoperative CT scan. The impact of potential risk factors on the occurrence of complications was assessed (age, worse initial clinical condition, any haemocoagulation disorder). RESULTS: Twenty patients died within the first month after surgery. Control CT scan showed one complication in 78 patients (83%), while 46 patients (49%) had more than one complication. We had to reoperate 22 patients (23.4%) due to a complication. The following complications were found: postoperative acute subgaleal/subdural haematoma (30× - 32%), subgaleal/subdural cerebrospinal fluid effusion (29× - 31%), soft tissues oedema (29× - 31%), haemorrhagic progression of brain contusion (17× - 18%), malignant brain oedema (8× - 8.5%), hydrocephalus (8× - 8.5%), temporal muscle atrophy (7× - 7.5%), peroperative massive bleeding ( 6× - 6.4%), epilepsy (4× - 4.3%), syndrome of the trephined (2× - 2.1%), skin necrosis (2× - 2.1%). Patients with a haemocoagulation disorder had a significantly higher incidence of complications (p=0.01). CONCLUSION: Complications of decompressive craniectomy after head injury are frequent. The potential benefit of decompressive craniectomy can be adversely affected by the occurrence of many complications.

[Radiation Necrosis in the Upper Cervical Spinal Cord in a Patient Treated with Proton Therapy after Radical Resection of the Fourth Ventricle Ependymoma]. / Radionekróza horní krcní míchy po protonovém ozárení u nemocné po radikální resekci ependymomu IV. komory mozkové.

BACKGROUND: Radiation necrosis in eloquent areas of the central nervous system (CNS) is one of the most serious forms of toxicity from radiation therapy. The occurrence of radiation necrosis in the CNS is described in a wide range of 3 months to 13 years after radiation therapy. The incidence of this complication covers a wide range of 3-47%. The potential advantage of proton therapy is the ability to reduce dose to normal tissue and escalate tumor dose. Proton beams enter and pass through the tissue with minimal dose deposition until they reach the end of their paths, where the peak of dose, known as the Bragg peak, occurs. Thereafter, a steep dose fall-off is evident. Such a precisely-distributed dose should reduce the toxicity of the treatment. PATIENT: A 23 year-old female patient underwent radical microsurgical resection of anaplastic ependymoma that originated from the floor of the fourth ventricle. The tumor was growing into the foramen magnum dorsally from the medulla oblongata. Taking into account the age of the patient, the localization of the tumor and the required dose of 60 Gy, proton therapy was chosen due to the lower risk of damage to the brain stem. Radiation therapy was performed using pencil beam scanning and one dorsal field. Following this course of treatment, radiation necrosis of the medulla oblongata and the upper cervical spinal cord occurred with fatal clinical impact on the patient. The article analyses possible causes of this complication and a review of the current literature is given. CONCLUSION: Despite the theoretical advantages of proton therapy, no clinical benefit in CNS tumors has yet been proven in comparison with modern methods of photon therapy. Proton therapy is accompanied by many uncertainties which can cause unpredictable complications, such as radiation necrosis at the edges of the target volume. Following proton therapy, there is not only a higher incidence of radiation necrosis but it occurs both sooner and to a higher degree. In cases of high anatomical complexity, the neurosurgeon should cooperate in the creation of the radiation treatment planning to ensure its optimization.Key words: brain tumors - ependymoma - radiation therapy - proton therapy - necrosis - radiation necrosis This work was partially supported by research project MH CZ - DRO (Faculty Hospital in Pilsen - FNPl, 00669806). The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers.Submitted: 29. 6. 2017Accepted: 25. 7. 2017.

Photonic crystal Fano laser: terahertz modulation and ultrashort pulse generation.

We suggest and analyze a laser with a mirror realized by Fano interference between a waveguide and a nanocavity. For small-amplitude modulation of the nanocavity resonance, the laser can be modulated at frequencies exceeding 1 THz, not being limited by carrier dynamics as for conventional lasers. For larger modulation, a transition from pure frequency modulation to the generation of ultrashort pulses is observed. The laser dynamics is analyzed by generalizing the field equation for conventional lasers to account for a dynamical mirror, described by coupled mode theory.

A comparison between experiment and theory on few-quantum-dot nanolasing in a photonic-crystal cavity.

We present an experimental and theoretical study on the gain mechanism in a photonic-crystal-cavity nanolaser with embedded quantum dots. From time-resolved measurements at low excitation power we find that four excitons are coupled to the cavity. At high excitation power we observe a smooth low-threshold transition from spontaneous emission to lasing. Before lasing emission sets in, however, the excitons are observed to saturate, and the gain required for lasing originates rather from multi-excitonic transitions, which give rise to a broad emission background. We compare the experiment to a model of quantum-dot microcavity lasers and find that the number of excitons that must be included to fit the data largely exceeds the measured number, which shows that transitions involving the wetting layer can provide a surprisingly large contribution to the gain.

Proposed quenching of phonon-induced processes in photoexcited quantum dots due to electron-hole asymmetries.

Differences in the confinement of electrons and holes in quantum dots are shown to profoundly impact the magnitude of scattering with acoustic phonons. Using an extensive model that includes the non-Markovian nature of the phonon reservoir, we show how the effect may be addressed by photoluminescence excitation spectroscopy of a single quantum dot. We also investigate the implications for cavity QED, i.e., a coupled quantum dot-cavity system, and demonstrate that the phonon scattering may be strongly quenched. The quenching is explained by a balancing between the deformation potential interaction strengths and the carrier confinement and depends on the quantum dot shape. Numerical examples suggest a route towards engineering the phonon scattering.

Bloch-wave engineering of quantum dot micropillars for cavity quantum electrodynamics experiments.

We have employed Bloch-wave engineering to realize submicron diameter high quality factor GaAs/AlAs micropillars (MPs). The design features a tapered cavity in which the fundamental Bloch mode is subject to an adiabatic transition to match the Bragg mirror Bloch mode. The resulting reduced scattering loss leads to record-high vacuum Rabi splitting of the strong coupling in MPs with modest oscillator strength quantum dots. A quality factor of 13, 600 and a splitting of 85 µeV with an estimated visibility v of 0.41 are observed for a small mode volume MP with a diameter d{c} of 850 nm.

Mitochondrial DNA differentiation between the antitropical blue whiting species Micromesistius poutassou and Micromesistius australis.

This study investigated the biogeography and genetic variation in the antitropically distributed Micromesistius genus. A 579 bp fragment of the mitochondrial coI gene was analysed in 279 individuals of Micromesistius poutassou and 163 of Micromesistius australis. The time since divergence was estimated to be c. 2 million years before present (Mb.p.) with an externally derived clock rate by Bayesian methods. Congruent estimates were obtained with an additional data set of cytochrome b sequences derived from GenBank utilizing a different clock rate. The divergence time of 2 Mb.p. was in disagreement with fossil findings in New Zealand and previous hypotheses which suggested the divergence to be much older. It, therefore, appears likely that Micromesistius has penetrated into the southern hemisphere at least two times. Paleoceanographic records indicate that conditions that would increase the likelihood for transequatorial dispersals were evident c. 2-1·6 Mb.p.. Haplotype frequency differences, along with pairwise F(ST) values, indicated that Mediterranean M. poutassou is a genetically isolated population.

Modulation response of nanoLEDs and nanolasers exploiting Purcell enhanced spontaneous emission.

The modulation bandwidth of quantum well nanoLED and nanolaser devices is calculated from the laser rate equations using a detailed model for the Purcell enhanced spontaneous emission. It is found that the Purcell enhancement saturates when the cavity quality-factor is increased, which limits the maximum achievable spontaneous recombination rate. The modulation bandwidth is thereby limited to a few tens of GHz for realistic devices.

Non-markovian model of photon-assisted dephasing by electron-phonon interactions in a coupled quantum-dot-cavity system.

We investigate the influence of electron-phonon interactions on the dynamical properties of a quantum-dot-cavity QED system. We show that non-markovian effects in the phonon reservoir lead to strong changes in the dynamics, arising from photon-assisted dephasing processes, not present in markovian treatments. A pronounced consequence is the emergence of a phonon induced spectral asymmetry when detuning the cavity from the quantum-dot resonance. The asymmetry can only be explained when considering the polaritonic quasiparticle nature of the quantum-dot-cavity system. Furthermore, a temperature induced reduction of the light-matter coupling strength is found to be relevant in interpreting experimental data, especially in the strong coupling regime.

[The curative effect of carotid endarterectomy]. / Kurativní efekt karotické endarterektomie.

The preventive effect of carotid endarterectomy in the reduction of ischemic stroke was reliably confirmed. Carotid endarterectomy may also be a curative method, but it has not been confirmed yet. In our case report we illustrate the curative effect of carotid endarterectomy in a patient after a combined embolic and hemodynamic stroke. The administration of intravenous thrombolysis did not have the expected clinical response. Neuroimaging showed ischemia and homolateral hypoperfusion of the brain hemisphere caused by critical internal carotid artery stenosis. On the 8th day after thrombolysis a carotid endarterectomy was performed with beneficial effect. Normalization of hemodynamic in the altered hemisphere was demonstrated by perfusion examination along with the clinical improvement. A curative effect of endarterectomy appears more probable in a hemodynamic ischemic stroke. For the improvement of a neuronal function the existence of penumbra is a condition. While a positive influence of hemodynamic by carotid endarterectomy is confirmed, the possibility of an increase in neuronal activity after repair of vasomotor activity is not documented. The curative effect and it's connection to the timing of the carotid endarterectomy require testing in the further studies.

[Intraoperative neuromonitoring, neuroprotection and preventive carotid endarterectomy in patients with increased risk for development of cerebral ischemia indicated for cardiosurgery]. / Postavení peroperacní neuromonitorace, neuroprotekce a preventivní karotické endarterektomie u nemocných se zvýseným rizikem mozkové ischemie indikovaných ke kardiochirurgické operaci.

AIM OF STUDY: To demonstrate the benefit of peroperative electrophysiological monitoring and neuroprotection in cardiac surgery that makes use a cardiopulmonary bypass in patients with a high risk of stroke and to analyze the importance of prophylactic carotid endarterectomy. BACKGROUND: Cerebral ischemia is the most dreaded complication of cardiovascular operations that make use of a cardiopulmonary bypass. It is necessary to select an approach that minimalizes neurological complications. In our treatment strategy we use preoperative electrophysiological monitoring and neuroprotection. Prophylactic carotid endarterectomy performed as part of a combined operation we performed in patients with a high risk of hemodynamic stroke. METHOD: We retrospectively evaluated 86 patients (2004-2008) after cardiac surgery that made use of a cardiopulmonary bypass and synchronous electrophysiological neuromonitoring. After any decrease in neuronal function neuroprotection was used. Combined carotid and cardiac operations were performed under one general anestesia in ten patients with a high risk of hemodynamic stroke. RESULTS: A peroperative decline in electrophysiological responses was noted in 76.5%, of these 54.5% were insignificant alterations, 42.4% significant and in two cases there was a total deletion. After administration of neuroprotection electrophysiological responses partially normalized in 14%, totally normalized in 60% and did not change in 26%. Only one permanent stroke and four temporary encephalopathy were identified after surgery. No morbidity/mortality were detected after combined operations. CONCLUSION: Peroperative electrophysiological neuromonitoring combined with neuroprotection eliminate cerebral ischemic complications in cardiac surgery that makes use of a cardiopulmonary bypass. Selected patients with high risk of hemodynamic stroke profit from carotid endarterectomy.

Numerical investigation of electromagnetically induced transparency in a quantum dot structure.

.A numerical investigation of pulse propagation in a quantum dot structure in the regime of electromagnetically induced transparency is reported. The quantum dot is described as a cone on top of a wetting layer and the calculated energy levels and dipole moments are used in an effective three-level model. Pulse propagation characteristics such as degree of slowdown, absorption, and pulse distortion are investigated with respect to their dependence on the dephasing rates and pulse width. It is seen how Rabi oscillations can seriously distort the pulse when the spectral width of the pulse becomes too large compared to the width of the EIT window.

Non-steroidal anti-inflammatory drugs and the risk of oral cancer: a nested case-control study.

BACKGROUND: Non-steroidal anti-inflammatory drugs (NSAIDs) seem to prevent several types of cancer, but could increase the risk of cardiovascular complications. We investigated whether use of NSAIDs was associated with a change in the incidence of oral cancer or overall or cardiovascular mortality. METHODS: We undertook a nested case-control study to analyse data from a population-based database (Cohort of Norway; CONOR), which consisted of prospectively obtained health data from all regions of Norway. People with oral cancer were identified from the 9241 individuals in CONOR who were at increased risk of oral cancer because of heavy smoking (15 pack-years), and matched controls were selected from the remaining heavy smokers (who did not have cancer). FINDINGS: We identified and analysed 454 (5%) people with oral cancer (279 men, 175 women, mean [SD] age at diagnosis 63.3 [13.2] years) and 454 matched controls (n=908); 263 (29%) had used NSAIDs, 83 (9%) had used paracetamol (for a minimum of 6 months), and 562 (62%) had used neither drug. NSAID use (but not paracetamol use) was associated with a reduced risk of oral cancer (including in active smokers; hazard ratio 0.47, 95% CI 0.37-0.60, p<0.0001). Smoking cessation also lowered the risk of oral cancer (0.41, 0.32-0.52, p<0.0001). Additionally, long-term use of NSAIDs (but not paracetamol) was associated with an increased risk of cardiovascular-disease-related death (2.06, 1.34-3.18, p=0.001). NSAID use did not significantly reduce overall mortality (p=0.17). INTERPRETATION: Long-term use of NSAIDs is associated with a reduced incidence of oral cancer (including in active smokers), but also with an increased risk of death due to cardiovascular disease. These findings highlight the need for a careful risk-benefit analysis when the long-term use of NSAIDs is considered.

7x 40 Gb/s base-rate RZ all-optical broadcasting utilizing an electroabsorption modulator.

We experimentally demonstrate all-optical broadcasting through simultaneous 7 x 40 Gb/s base-rate wavelength conversion in RZ format based on cross absorption modulation in an electroabsorption modulator. In this experiment the original intensity-modulated information is successfully duplicated onto seven wavelengths that comply with the ITU-T proposal. The advantages of the proposed wavelength conversion scheme are also discussed.

Separation of coherent and incoherent nonlinearities in a heterodyne pump-probe experiment.

We demonstrate that the transient coherent nonlinearity (coherent artifact) affecting the pump-probe response of semiconductor optical amplifiers can be experimentally separated from the incoherent transient. The technique is based on measuring the mirror component of the coherent artifact which is a background-free four--wave mixing signal at a different frequency with respect to the transmitted probe in a heterodyne detection scheme. Measurements on amplifiers of different length reveal strong deviations from the commonly expected symmetric shape of the coherent artifact in case of long waveguides.

Head and neck cancer in Norway. A study of the quality of the Cancer Registry of Norway's data on head and neck cancer for the period 1953-1991.

Data from population-based cancer registries provide information on the causes and outcome of cancer and form a basis for important decision making in connection with the prevention of cancer and the planning of health services. This makes it of the utmost importance to assess the data at all stages of collection to ensure the highest possible quality. The present study focuses on the quality of the Cancer Registry of Norway's data on head and neck cancer for the period 1953-1991. When the study was started, 16,104 cases of head and neck malignancies had been registered. All histological codes were reviewed. The pathologists' reports were reevaluated for 369 cases selected according to set criteria: 133 cases received a new histological code without being excluded from the data material: 112 cases were excluded. The distribution of histological diagnoses for each location is presented. A reevaluation of 300 cases selected at random from the corrected series indicates discrepancies between the pathologist's classification and the Registry's coding in less than 2% (1.4%) of all cases. The percentage that lacked histological verification fell from 5.7% in the first decade to 2.1% during the last 9-year period. Completeness of the Cancer Registry's data base was checked against hospital-based registries and this investigation showed that virtually all new cases are reported. We conclude that the data on head and neck cancer for the studied time period meet standards that justify their use as a basis for epidemiological as well as clinical studies.

Dephasing times in quantum dots due to elastic LO phonon-carrier collisions

Interpretation of experiments on quantum dot (QD) lasers presents a challenge: the phonon bottleneck, which should strongly suppress relaxation and dephasing of the discrete energy states, often seems to be inoperative. We suggest and develop a theory for an intrinsic mechanism for dephasing in QDs: second-order elastic interaction between quantum dot charge carriers and LO phonons. The calculated dephasing times are of the order of 200 fs at room temperature, consistent with experiments. The phonon bottleneck thus does not prevent significant room temperature dephasing.

Familial risk in head and neck squamous cell carcinoma diagnosed before the age of 45: a population-based study.

This population-based study analyses familial risk as a factor in the development of head and neck squamous cell carcinoma before the age of 45. Two different designs were used: (1) estimation of standardised incidence ratios (SIRs) for cancer among first-degree relatives of 127 young head and neck cancer probands; and (2) estimation of odds ratios (ORs) for developing head and neck cancer associated with cancer in a first-degree relative. SIRs of cancer of the respiratory and upper digestive tract (lungs, oesophagus, and smoking-related head and neck sites [RUDT]) for first-degree relatives were 4.3 (95% confidence intervals or 95% CI of 1.6-9.5) for female patients, 1.0 (95% CI = 0.3-2.6) for male patients and 1.9 (95% CI = 0.9-3.5) for both sexes combined. ORs for head and neck cancer before the age of 45, in association with cancer of RUDT in a first-degree relative were 5.0 (95% CI = 1.4-17.3) for women, 1.1 (95% CI = 0.3-3.3) for men, and 2.0 (95% CI = 0.9-4.4) for both sexes combined. Hence, when analysing both sexes combined, our familial risk estimates for head and neck cancer showed non-significant increases. An explanation for the unexpected sex asymmetry in familial risk could be an interaction between inherent cancer susceptibility and a female biological characteristic. Alternatively, it could be artefacts caused by differences in familial smoking habits.

Forty years of monitoring head and neck cancer in Norway--no good news.

BACKGROUND: Male incidence rates of head and neck cancer are rising in most regions of the world. This paper describes Norwegian time trends in male incidence and relative survival from cancer of major head and neck sites. MATERIAL AND METHODS: The presentation comprises the entire Norwegian male population from 1955 to 1994. Incidence rates and relative survival rates were calculated for cancer of oral sites, oro-/hypopharynx and larynx separately. RESULTS: Age-adjusted incidence rates of oral and pharyngeal cancer increased after 1970 by 11 percent per 5-year period (95% CI: 5-19) and 14 percent per 5-year period (95% CI: 4-24), respectively. Laryngeal cancer incidence increased after 1955 by 14 percent per 5-year period (95% CI: 7-21). There were only small improvements in 5-year relative survival rates from oral and pharyngeal cancer. CONCLUSION: Male incidence rates increased for all the studied sites during the observation period. The prognosis for the patient groups included in this presentation has not improved substantially since the 1950's.

Application of a Medical Text Indexer to an online dermatology atlas.

Clinical dermatology cases are presented as images and semi-structured text describing skin lesions and their relationships to disease. Metadata assignment to such cases is hampered by lack of a standardized dermatology vocabulary and facilitated methods for indexing legacy collections. In this pilot study descriptive clinical text from Dermatlas, a Web-based repository of dermatology cases, was indexed to Medical Subject Heading (MeSH) terms using the National Library of Medicine's Medical Text Indexer (MTI). The MTI is an automated text processing system that derives ranked lists of MeSH terms to describe the content of medical journal citations using knowledge from the Unified Medical Language System (UMLS) and from MEDLINE. For a representative, random sample of 50 Dermatlas cases, the MTI frequently derived MeSH indexing terms that matched expert-assigned terms for Diagnoses (88%), Lesion Types (72%), and Patient Characteristics (Gender and Age Groups, 62% and 84% respectively). This pilot demonstrates the potential for extending the MTI to automate indexing of clinical case presentations and for using MeSH to describe aspects of clinical dermatology.