Factors affecting periodontal disease referral and the adherence to guidelines among general dentists.

BACKGROUND: Current research highlights a need to investigate the factors affecting periodontal disease referral. Limited literature exists on periodontal disease referral in Australia and no comparison to the periodontal disease referral guidelines exists. OBJECTIVE: This study analyses the factors affecting periodontal disease referral and the adherence to guidelines in general dentists in Queensland, Australia. METHODS: Fifty-seven general dentists who are members of the Australian Dental Association (Queensland) undertook an online survey. RESULTS: The disease factor regarded as most important (90% of respondents) was unresolved inflammation upon re-evaluation. The non-disease factor regarded as most important (79% of respondents) was the operator's level of training. There is low awareness of the guidelines (36.7%) yet a reasonable adherence to them (78.3%). Of those aware of the guidelines, there was a statistically significant poorer adherence to the guidelines compared to those unaware (P = 0.036), while there is no significant difference in the adherence to guidelines between those who have and those who have not attended continuing professional development (CPD) courses (P = 0.66). CONCLUSIONS: Adherence to current guidelines is not significantly impacted by the level of awareness of the guidelines or CPD attendance. The results from this study suggest a need to refine the current guidelines to better inform decisions about periodontal disease referrals.

Selective recovery of striatal 125I-alpha-conotoxinmii nicotinic receptors after nigrostriatal damage in monkeys.

Evidence suggests that nicotinic receptors play a role in nigrostriatal function, a finding that may be relevant to Parkinson's disease. Knowledge of the conditions that regulate nicotinic receptor expression is therefore important. Previous studies showed that several different nicotinic receptors, including alpha-conotoxinMII (alpha-CtxMII)-sensitive receptors, are decreased after nigrostriatal damage. Nigrostriatal dopaminergic terminals also demonstrate a capacity for recovery after lesioning. The present experiments were therefore done to determine whether there were changes in striatal nicotinic receptors with recovery. To address this, we used two well-characterized animal models of nigrostriatal damage produced using the selective dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Studies in mice showed that striatal 125I-alpha-CtxMII, as well as 125I-epibatidine and 125I-A85380 binding sites significantly recovered 1 month after lesioning, suggesting that alpha6* and most likely alpha4* receptors are increased. Experiments were next done in monkeys since striatal 125I-alpha-CtxMII receptors constitute a large percentage of nicotinic receptors and are more vulnerable to nigrostriatal damage in this model that closely mirrors Parkinson's disease. In monkeys allowed to recover from the toxic effects of MPTP for a 1-2 year period, there was a significant improvement in the Parkinson disability score. There was also a reversal in lesion-induced declines in striatal alpha-CtxMII-sensitive receptors, but no significant change in 125I-epibatidine and 125I-A85380 receptors. These findings suggest that alpha3*/alpha6* sites are selectively increased in monkey striatum with recovery. The present data show that recovery of 125I-alpha-CtxMII receptors occurs in parallel with the dopamine transporter, indicating that these nicotinic receptors sites are localized to presynaptic dopamine terminals in both species.

A local training and pruning approach for neural networks.

The training of neural networks using the extended Kalman filter (EKF) algorithm is plagued by the drawback of high computational complexity and storage requirement that may become prohibitive even for networks of moderate size. In this paper, we present a local EKF training and pruning approach that can solve this problem. In particular, the by-products obtained along with the local EKF training can be utilized to measure the importance of the network weights. Comparing with the original global approach, the proposed local EKF training and pruning approach results in a much lower computational complexity and storage requirement. Hence, it is more practical in solving real world problems. The performance of the proposed algorithm is demonstrated on one medium- and one large-scale problems, namely, sunspot data prediction and handwritten digit recognition.

An adaptive Bayesian pruning for neural networks in a non-stationary environment.

Pruning a neural network to a reasonable smaller size, and if possible to give a better generalization, has long been investigated. Conventionally the common technique of pruning is based on considering error sensitivity measure, and the nature of the problem being solved is usually stationary. In this article, we present an adaptive pruning algorithm for use in a nonstationary environment. The idea relies on the use of the extended Kalman filter (EKF) training method. Since EKF is a recursive Bayesian algorithm, we define a weight-importance measure in term of the sensitivity of a posteriori probability. Making use of this new measure and the adaptive nature of EKF, we devise an adaptive pruning algorithm called adaptive Bayesian pruning. Simulation results indicate that in a noisy nonstationary environment, the proposed pruning algorithm is able to remove network redundancy adaptively and yet preserve the same generalization ability.

Analysis for a class of winner-take-all model.

Recently we have proposed a simple circuit of winner-take-all (WTA) neural network. Assuming no external input, we have derived an analytic equation for its network response time. In this paper, we further analyze the network response time for a class of winner-take-all circuits involving self-decay and show that the network response time of such a class of WTA is the same as that of the simple WTA model.

On the Kalman filtering method in neural network training and pruning.

In the use of extended Kalman filter approach in training and pruning a feedforward neural network, one usually encounters the problems on how to set the initial condition and how to use the result obtained to prune a neural network. In this paper, some cues on the setting of the initial condition will be presented with a simple example illustrated. Then based on three assumptions--1) the size of training set is large enough; 2) the training is able to converge; and 3) the trained network model is close to the actual one, an elegant equation linking the error sensitivity measure (the saliency) and the result obtained via extended Kalman filter is devised. The validity of the devised equation is then testified by a simulated example.

On the regularization of forgetting recursive least square.

In this paper, the regularization of employing the forgetting recursive least square (FRLS) training technique on feedforward neural networks is studied. We derive our result from the corresponding equations for the expected prediction error and the expected training error. By comparing these error equations with other equations obtained previously from the weight decay method, we have found that the FRLS technique has an effect which is identical to that of using the simple weight decay method. This new finding suggests that the FRLS technique is another on-line approach for the realization of the weight decay effect. Besides, we have shown that, under certain conditions, both the model complexity and the expected prediction error of the model being trained by the FRLS technique are better than the one trained by the standard RLS method.

Extended Kalman Filter-Based Pruning Method for Recurrent Neural Networks.

Pruning is one of the effective techniques for improving the generalization error of neural networks. Existing pruning techniques are derived mainly from the viewpoint of energy minimization, which is commonly used in gradient-based learning methods. In recurrent networks, extended Kalman filter (EKF)-based training has been shown to be superior to gradient-based learning methods in terms of speed. This article explains a pruning procedure for recurrent neural networks using EKF training. The sensitivity of a posterior probability is used as a measure of the importance of a weight instead of error sensitivity since posterior probability density is readily obtained from this training method. The pruning procedure is tested using three problems: (1) the prediction of a simple linear time series, (2) the identification of a nonlinear system, and (3) the prediction of an exchange-rate time series. Simulation results demonstrate that the proposed pruning method is able to reduce the number of parameters and improve the generalization ability of a recurrent network.

Knee adduction moment, serum hyaluronan level, and disease severity in medial tibiofemoral osteoarthritis.

OBJECTIVE: The adduction moment at the knee during gait is the primary determinant of medial-to-lateral load distribution. If the adduction moment contributes to progression of osteoarthritis (OA), then patients with advanced medial tibiofemoral OA should have higher adduction moments. The present study was undertaken to investigate the hypothesis that the adduction moment normalized for weight and height is associated with medial tibiofemoral OA disease severity after controlling for age, sex, and pain level, and to examine the correlation of serum hyaluronan (HA) level with disease severity and with the adduction moment in a subset of patients. METHODS: Fifty-four patients with medial tibiofemoral OA underwent gait analysis and radiographic evaluation. Disease severity was assessed using the Kellgren-Lawrence (K-L) grade and medial joint space width. In a subset of 23 patients with available sera, HA was quantified by sandwich enzyme-linked immunosorbent assay. Pearson correlations, a random effects model, and multivariate regression models were used. RESULTS: The adduction moment correlated with the K-L grade in the left and right knees (r = 0.68 and r = 0.60, respectively), and with joint space width in the left and right knees (r = -0.45 and r = -0.47, respectively). The relationship persisted after controlling for age, sex, and severity of pain. The partial correlation between K-L grade and adduction moment was 0.71 in the left knees and 0.61 in the right knees. For every 1.0-unit increase in adduction moment, there was a 0.63-mm decrease in joint space width. In the subset of patients in whom serum HA levels were measured, HA levels correlated with medial joint space width (r = -0.55), but not with the adduction moment. CONCLUSION: There is a significant relationship between the adduction moment and OA disease severity. Serum HA levels correlate with joint space width but not with the adduction moment. Longitudinal studies will be necessary to determine the contribution of the adduction moment, and its contribution in conjunction with metabolic markers, to progression of medial tibiofemoral OA.

A point cluster method for in vivo motion analysis: applied to a study of knee kinematics.

A new method for deriving limb segment motion from markers placed on the skin is described. The method provides a basis for determining the artifact associated with nonrigid body movement of points placed on the skin. The method is based on a cluster of points uniformly distributed on the limb segment. Each point is assigned an arbitrary mass. The center of mass and the inertia tensor of this cluster of points are calculated. The eigenvalues and eigenvectors of the inertia tensor are used to define a coordinate system in the cluster as well as to provide a basis for evaluating non-rigid body movement. The eigenvalues of the inertia tensor remain invariant if the segment is behaving as a rigid body, thereby providing a basis for determining variations for nonrigid body movement. The method was tested in a simulation model where systematic and random errors were introduced into a fixed cluster of points. The simulation demonstrated that the error due to nonrigid body movement could be substantially reduced. The method was also evaluated in a group of ten normal subjects during walking. The results for knee rotation and translation obtained from the point cluster method compared favorably to results previously obtained from normal subjects with intra-cortical pins placed into the femur and tibia. The resulting methodology described in this paper provides a unique approach to the measurement of in vivo motion using skin-based marker systems.

Patellofemoral design influences function following total knee arthroplasty.

The functional influence of patellofemoral design was evaluated by testing two cohorts of patients with total knee arthroplasty while walking, climbing stairs, and rising from a chair. The two cohorts received one of two different designs of total knee arthroplasty. The designs differed primarily in the curvature of the femoral trochlea. These differences in curvature have been shown in in vitro studies to influence the tracking of the patella. One design had a smaller radius on the patellar flange, which caused the patella to articulate more anteriorly and distally than the second design, which had a larger radius in this region. The second design more closely replicated the curvature of the femoral trochlear anatomy. There was a significant functional difference during stairclimbing between the patient groups, whereas there was no difference during walking or chair rising. The group with the design that had nonanatomic tracking of the patella had a higher than normal moment tending to flex the knee (net quadriceps moment) during late stance phase. The increased net quadriceps moment during late stance was concurrent with an increased knee flexion. The abnormal function occurred when the patellar was tracking over the nonanatomic portion of the trochlea. Patients in the group with the anatomic trochlea did not have abnormal function. These results suggest a relationship between a nonanatomic trochlea and abnormal function during stair-climbing.

Yet another algorithm which can generate topography map.

This paper presents an algorithm to form a topographic map resembling to the self-organizing map. The idea stems on defining an energy function which reveals the local correlation between neighboring neurons. The larger the value of the energy function, the higher the correlation of the neighborhood neurons. On this account, the proposed algorithm is defined as the gradient ascent of this energy function. Simulations on two-dimensional maps are illustrated.

Attraction basin of bidirectional association memories.

In this paper, we investigate the attraction basin of the bidirectional associative memory (BAM) model. The BAM is a two-layer heteroassociator that stores a prescribed set of bipolar library pairs. It consists of two layers of neurons. One layer has n neurons and the other has p neurons. We will first point out why the conventional energy approach cannot tell us about the attraction basin of each library pair. We then rigorously derive the statistical dynamics of the BAM, which shows how the upper bound on the number of errors changes during recalling for an arbitrary error pattern in the initial state. From the dynamics, we can estimate the attraction basin for the worst case errors, as well as the memory capacity and the number of errors in the retrieved pairs. The memory capacity is alpha rn, where alpha r (0 < alpha r < 1) depends on the ratio [formula: see text]. The number of errors in the retrieved pairs is [formula: see text] when the number of library pairs is alpha n. When r = 1, the lower bound on the attraction basin for the worst case errors is about 0.0068n.

Predictive value of EEG for outcome and epilepsy following neonatal seizures.

The value of the electroencephalogram in predicting outcome and epilepsy was examined in neonates who had experienced EEG-confirmed neonatal seizures. Electroencephalogram, neuroimaging studies, and other clinical variables were systematically analyzed in 81 consecutive neonates with EEG-confirmed seizures. The surviving subjects were followed for a mean of 17 months to determine if they developed post-neonatal seizures (PNS) and abnormal neurodevelopmental outcome. Several EEG variables were correlated with neurodevelopmental outcome and PNS when analyzed with univariate and multivariate statistical analyses. The EEG background activity and the presence of status epilepticus were strong predictors of outcome, but were not associated with PNS. The presence of rhythmic theta-alpha bursts was highly favorable for both outcome and PNS. In the interictal EEG, the number of negative sharp waves in the temporal region correlated with outcome and PNS. Clinical variables associated with unfavorable outcomes included an abnormal neonatal neurologic exam and certain seizure etiologies (e.g. cerebral dysgenesis and infections). Global abnormalities on neuroimaging studies were invariably associated with an unfavorable outcome and with the development of PNS in 66% of cases. Using multivariate analysis, prediction of outcome (favorable versus unfavorable) was accurately achieved in 85% of cases when combining EEG variables with neuroimaging and clinical findings. In conclusion, in neonates with EEG-confirmed seizures, the EEG is a useful predictor of outcome, but is a less useful predictor of PNS.

Functional MRI measurement of language lateralization in Wada-tested patients.

In this study the use of functional MRI (fMRI) for measuring language lateralization non-invasively was examined. The subjects were seven patients with histories of temporal lobe epilepsy who had undergone Wada testing for pre-surgical evaluation. Four patients were left-hemisphere-dominant and three were right-hemisphere-dominant for language. They received fMRI scans while they made semantic or perceptual judgments about visually presented words. Regions of the inferior frontal gyrus (pars triangularis and pars orbitalis) and neighbouring orbital cortex, corresponding to portions of Brodmann areas 45, 46 and 47, exhibited significant increases in activation during semantic relative to perceptual judgments. Lateralization of the increases in activation were consistent with the Wada test assessments of hemispheric language dominance in each of the seven patients. These results suggest that, in addition to providing a tool for investigating human cognitive processes, fMRI has significant clinical potential as a non-invasive measure of language lateralization.

Predictive value of the first ictal recording in determining localization of the epileptogenic region by scalp/sphenoidal EEG.

The number of seizures recorded during a noninvasive evaluation for epilepsy surgery varies across centers. We retrospectively studied the accuracy of the first recorded seizure in predicting the final localization of the epileptogenic region. Sixty-six consecutive patients undergoing continuous EEG monitoring with scalp and sphenoidal electrodes were studied. The first recorded seizure was determined to be either well localized or nonlocalized and was compared with the ultimate localization after multiple seizures were recorded. The first seizure was well localized in 28 and nonlocalized in 38 patients. In the localized group, the first seizure correctly predicted the final localization of the EEG monitoring study in 26 patients, whereas 2 patients had bilateral independent temporal seizures. In the nonlocalized group, ictal onset remained nonlocalized in 34 patients despite recording of multiple (median of five) seizures. This gave a sensitivity of 87% and specificity of 94% for the first recorded seizure to predict the final results of noninvasive EEG monitoring. We conclude that the first recorded seizure is highly predictive of the final results of prolonged noninvasive ictal EEG recordings but it cannot exclude the possibility of multiple epileptogenic foci.

Intracerebral involvement in scleroderma en coup de sabre: report of a case with neuropathologic findings.

Linear scleroderma en coup de sabre (LScs) is a rare disorder not infrequently associated with neurologic symptoms, notably epilepsy. However, histopathologic documentation of intracerebral lesions in LScs is very limited and the etiology of the central nervous system symptoms has therefore never been convincingly established. We describe a 27-year-old woman with LScs and a longstanding history of epilepsy. Radiographic studies demonstrated a focal, intraparenchymal lesion in the left frontal lobe directly subjacent to the area of scleroderma on the forehead and scalp. The resected cerebral lesion revealed localized band-like sclerosis of the leptomeninges and associated vessels, as well as intraparenchymal calcifications and anomalous, ectatic vessels. These findings suggest that LScs may represent a neurocutaneous syndrome of vascular dysplasia similar to the Sturge-Weber syndrome, rather than a localized form of collagen vascular disease, as suggested by some.

Unusual MRI findings after status epilepticus due to cat-scratch disease.

A 4-year-old girl with status epilepticus and severe encephalopathy associated with cat-scratch disease is described. She had prolonged seizures lasting more than 2 weeks and required treatment with pentobarbital coma. She developed unusual abnormalities on magnetic resonance imaging scans that involved the thalami and the cortex of the temporal, parietal, and occipital lobes. She has developed a persistent encephalopathy manifesting as visual disturbance and frequent partial seizures.

Selective death of immature neurons in methylmalonic acidemia of the neonate: a case report.

We report the clinical and post-mortem findings in a 4-day-old female infant with methylmalonic acidemia (MMA) prematurely delivered at 36 weeks gestation. Complementation analysis revealed a defect in methylmalonyl-CoA mutase apoenzyme activity. There was selective cell death of immature neurons involving germinal matrix, migrating neuroblasts, and both external and internal granular cell layers of the cerebellum and dentate gyrus of the hippocampus. Karyorrhexis was also seen in the lymphoid follicles of spleen, lymph nodes and in the thymus. Additionally, the spinal nerve roots demonstrated optically empty spaces in their myelin sheaths due to adaxonal separation of their myelin lamellae.