Vestibular schwannoma surgery has evolved as new therapeutic options have emerged, patients' expectations have risen, and the psychological effect of facial nerve paralysis has been studied. For ...large vestibular schwannomas for which extirpation is the primary therapy, the goals remain complete tumor resection and maintenance of normal neurological function. Improved microsurgical techniques and intraoperative facial nerve monitoring have decreased the complication rate and increased the likelihood of normal to near-normal postoperative facial function. Nevertheless, the impairment most frequently reported by patients as an adverse effect of surgery continues to be facial nerve paralysis. In addition, patient assessment has provided a different, less optimistic view of outcome. The authors evaluated the extent of facial function, timing of facial nerve recovery, patients' perceptions of this recovery and function, and the prognostic value of intraoperative facial nerve monitoring following resection of large vestibular schwannomas; they then analyzed these results with respect to different surgical approaches.
The authors retrospectively reviewed a database of 67 patients with 71 vestibular schwannomas measuring 3 cm or larger in diameter. The patients had undergone surgery via translabyrinthine, retrosigmoid, or combined approaches. Clinical outcomes were analyzed with respect to intraoperative facial nerve activity, responses to intraoperative stimulation, and time course of recovery. Eighty percent of patients obtained normal to near-normal facial function (House-Brackmann Grades I and II). Patients' perceptions of facial nerve function and recovery correlated well with the clinical observations.
Trends in the data lead the authors to suggest that a retrosigmoid exposure, alone or in combination with a translabyrinthine approach, offers the best chance of facial nerve preservation in patients with large vestibular schwannomas.
Introduction:
Presently there are several options available to patients with acoustic tumors. Information concerning recurrences following treatment of acoustic tumors is important to the ...decision-making process and informed consent. A consecutive series of 540 patients with acoustic tumors who underwent resection as primary treatment were followed for a mean of 7.5 years. Results with regard to residual and recurrent tumors are reported and analyzed.
Methods:
In addition to maintaining a database (Microsoft Access) concerning this group of patients, additional follow-up visits, telephone questionnaires, correspondence from referring physicians, and 1-, 3-, and 6-year MRI scans were used to obtain results.
Results:
Of 540 patients analyzed, we were able to document 8 recurrent or residual tumors, 3 of which were re-resected.
Conclusions:
There continues to be a paucity of literature documenting the frequency of residual or recurrent tumors requiring treatment following attempted complete microsurgical resection. A low incidence of tumor recurrence was noted after successful microresection of acoustic tumors in this series. Enhancing lesions in the distal internal auditory canal (IAC) on MRI at 1 year postop are predictive of growing recurrent acoustic neuromas at 3 years. A negative MRI at 1 year postop is highly predictive of no recurrence at 3 and 6 years.
Up to 4 million patients with signs of myocardial ischemia have no obstructive coronary artery disease (CAD). The absence of precise guidelines for diagnosis and treatment in non-obstructive CAD ...encourages the scientific community to fill the gap knowledge, to provide non-invasive and less expensive diagnostic tools. The aim of our study was to explore the biological profile of Ischemia with Non-Obstructive Coronary Arteries (INOCA) patients with microvascular dysfunction compared to patients presenting with obstructive chronic coronary syndrome (ObCCS) in order to find specific hallmarks of each clinical condition. We performed a gene expression array from peripheral blood mononuclear cells (PBMCs) isolated from INOCA (n = 18) and ObCCS (n = 20) patients. Our results showed a significantly reduced gene expression of molecules involved in cell adhesion, signaling, vascular motion, and inflammation in INOCA as compared to the ObCCS group. In detail, we found lower expression of Platelet and Endothelial Cell Adhesion Molecule 1 (CD31, p < 0.0001), Intercellular Adhesion Molecule-1 (ICAM1, p = 0.0004), Tumor Necrosis Factor (TNF p = 0.0003), Transferrin Receptor (TFRC, p = 0.002), and Vascular Endothelial Growth Factor A (VEGFA, p = 0.0006) in the INOCA group compared with ObCCS. Meanwhile, we observed an increased expression of Hyaluronidase (HYAL2, p < 0.0001) in INOCA patients in comparison to ObCCS. The distinct expression of molecular biomarkers might allow an early and non-invasive differential diagnosis between ObCCS and INOCA, improving clinical management and treatment options, in the era of personalized medicine.
In this paper we obtain asymptotic expansions for the nonnull distribution functions of the likelihood ratio, score and Wald test statistics in exponential family generalised linear models under ...Pitman alternatives assuming unknown dispersion, thus generalising some of the results in Cordeiro, Botter & Ferrari (1994).
We propose a new pivotal quantity which is a function of the maximum likelihood estimate of a scalar parameter θ and whose distribution is standard normal excluding terms of order
and smaller, where ...n is the sample size. The proposed pivot is a polynomial transformation of the standardized maximum likelihood estimate of at most third degree. We apply our main result to the one-parameter exponential family model and to a number of special distributions of this family. Some simulation results illustrate the superiority of our pivotal quantity over the usual standardized maximum likelihood estimate with regard to third-order asymptotic theory.
Bias reduction in one-parameter exponential family models Cribari-Neto, Francisco; Botter, Denise A.; Cordeiro, Gauss M. ...
Communications in statistics. Simulation and computation,
19/1/1/, Letnik:
27, Številka:
3
Journal Article
Recenzirano
This paper gives closed-form expressions for the second and third order biases of maximum likelihood estimates for a number of distributions in the one-parameter exponential family. Approximations ...based on asymptotic expansions for some bias-corrections that require the evaluation of unusual functions and long expressions are given. A graphical analysis is also performed to show how such biases and the mean squared errors of both the maximum likelihood estimate and its bias-corrected version vary with the parameter that indexes some distributions. Finally, we present simulation results comparing the performance of the maximum likelihood estimator and its bias-corrected version.
In this paper we derive second- and third-order bias-corrected maximum likelihood estimates in general uniparametric models. We compare the corrected estimates and the usual maximum likelihood ...estimate in terms of their mean squared errors. We also obtain closed-form expressions for bias-corrected estimates in one-parameter exponential family models. Our results cover many important and commonly used distributions. Simulation results are also given.
