Painless progressive mononeuritis multiplex secondary to AML associated neuroleukemiosis

Neuroleukemiosis describes peripheral nerve involvement secondary to leukemic infiltration, a rare complication of leukemia with various clinical presentations, leading to diagnostic challenges for hematologists and neurologists. We present two cases of painless progressive mononeuritis multiplex secondary to neuroleukemiosis. A literature review of previously reported cases of neuroleukemiosis was undertaken. Neuroleukemiosis may present as a progressive mononeuritis multiplex. The diagnosis of neuroleukemiosis requires a high index of suspicion and be aided by repeated CSF analysis.

The intrinsic plasticity of medial vestibular nucleus neurons during vestibular compensation-a systematic review and meta-analysis

BACKGROUND

Vestibular compensation is a homeostatic process that occurs in the central nervous system in response to peripheral vestibular dysfunction. Experimental studies in rodent models have suggested that unilateral peripheral vestibular lesions are correlated with an increase in the intrinsic excitability of central vestibular neurons. This process may be dependent on the intrinsic properties of the neurons themselves. We aimed to conduct a systematic review of the literature to survey the evidence for changes in intrinsic plasticity observed during the acute phase of vestibular compensation.

METHODS

We systematically reviewed the literature regarding the electrophysiological effect of experimentally induced unilateral vestibular deafferentation (UVD) on the intrinsic membrane properties of medial vestibular nucleus neurons in animal models. We developed tools to assess the methodological quality (precision, validity and bias) of studies that met pre-determined inclusion and exclusion criteria. We extracted numerical data and performed a meta-analysis of specific quantitative data pooled from these studies.

RESULTS

We identified 17 studies that satisfied the inclusion criteria. There is moderate quality evidence to suggest a statistically significant increase in the intrinsic excitability of medial vestibular nucleus neurons following unilateral vestibular deafferentation. Specifically, the spontaneous discharge rate increases by 4 spikes/s on average and the sensitivity to current stimuli increases.

CONCLUSION

Using this novel approach, we demonstrate that the methodology of systematic review and meta-analysis is a useful tool in the summation of data across experimental animal studies with similar aims.

Vestibular Interactions in the Thalamus

It has long been known that the vast majority of all information en route to the cerebral cortex must first pass through the thalamus. The long held view that the thalamus serves as a simple hi fidelity relay station for sensory information to the cortex, however, has over recent years been dispelled. Indeed, multiple projections from the vestibular nuclei to thalamic nuclei (including the ventrobasal nuclei, and the geniculate bodies)- regions typically associated with other modalities- have been described. Further, some thalamic neurons have been shown to respond to stimuli presented from across sensory modalities. For example, neurons in the rat anterodorsal and laterodorsal nuclei of the thalamus respond to visual, vestibular, proprioceptive and somatosensory stimuli and integrate this information to compute heading within the environment. Together, these findings imply that the thalamus serves crucial integrative functions, at least in regard to vestibular processing, beyond that imparted by a “simple” relay. In this mini review we outline the vestibular inputs to the thalamus and provide some clinical context for vestibular interactions in the thalamus. We then focus on how vestibular inputs interact with other sensory systems and discuss the multisensory integration properties of the thalamus.

Efferent Vestibular Neurons Show Homogenous Discharge Output But Heterogeneous Synaptic Input Profile In Vitro

Despite the importance of our sense of balance we still know remarkably little about the central control of the peripheral balance system. While previous work has shown that activation of the efferent vestibular system results in modulation of afferent vestibular neuron discharge, the intrinsic and synaptic properties of efferent neurons themselves are largely unknown. Here we substantiate the location of the efferent vestibular nucleus (EVN) in the mouse, before characterizing the input and output properties of EVN neurons in vitro. We made transverse serial sections through the brainstem of 4-week-old mice, and performed immunohistochemistry for calcitonin gene-related peptide (CGRP) and choline acetyltransferase (ChAT), both expressed in the EVN of other species. We also injected fluorogold into the posterior canal and retrogradely labelled neurons in the EVN of ChAT:: tdTomato mice expressing tdTomato in all cholinergic neurons. As expected the EVN lies dorsolateral to the genu of the facial nerve (CNVII). We then made whole-cell current-, and voltage-clamp recordings from visually identified EVN neurons. In current-clamp, EVN neurons display a homogeneous discharge pattern. This is characterized by a high frequency burst of action potentials at the onset of a depolarizing stimulus and the offset of a hyperpolarizing stimulus that is mediated by T-type calcium channels. In voltage-clamp, EVN neurons receive either exclusively excitatory or inhibitory inputs, or a combination of both. Despite this heterogeneous mixture of inputs, we show that synaptic inputs onto EVN neurons are predominantly excitatory. Together these findings suggest that the inputs onto EVN neurons, and more specifically the origin of these inputs may underlie EVN neuron function.

Intrinsic neuronal excitability: implications for health and disease

The output of a single neuron depends on both synaptic connectivity and intrinsic membrane properties. Changes in both synaptic and intrinsic membrane properties have been observed during homeostatic processes (e.g., vestibular compensation) as well as in several central nervous system (CNS) disorders. Although changes in synaptic properties have been extensively studied, particularly with regard to learning and memory, the contribution of intrinsic membrane properties to either physiological or pathological processes is much less clear. Recent research, however, has shown that alterations in the number, location or properties of voltage- and ligand-gated ion channels can underlie both normal and abnormal physiology, and that these changes arise via a diverse suite of molecular substrates. The literature reviewed here shows that changes in intrinsic neuronal excitability (presumably in concert with synaptic plasticity) can fundamentally modify the output of neurons, and that these modifications can subserve both homeostatic mechanisms and the pathogenesis of CNS disorders including epilepsy, migraine, and chronic pain.

Total agranulocytosis caused by dapsone therapy for tuberculoid leprosy--an unappreciated serious side effect of anti-leprosy treatment with clinical implications

Dapsone-induced agranulocytosis is a rare but potentially fatal adverse effect of treatment for tuberculoid leprosy. Publications distributed by the WHO Leprosy Elimination Campaign for patient information on leprosy do not contain any advice or guidelines for post-dapsone therapy follow-up. As a result of this major deficiency, the local anti-leprosy campaign in Sri Lanka has no such guidelines on dapsone therapy for leprosy patients. We report two patients with total agranulocytosis caused by dapsone therapy for tuberculoid leprosy including one fatality. As leprosy is more prevalent in developing countries such as Sri Lanka, we recommend that WHO publications on patient information should include post-dapsone therapy follow-up guidelines to avoid such catastrophes which are undetected until the patients are critically ill.

The mental prosthesis: assessing the speed of a P300-based brain-computer interface

We describe a study designed to assess a brain-computer interface (BCI), originally described by Farwell and Donchin [9] in 1988. The system utilizes the fact that the rare events in the oddball paradigm elicit the P300 component of the event-related potential (ERP). The BCI presents the user with a matrix of 6 by 6 cells, each containing one letter of the alphabet. The user focuses attention on the cell containing the letter to be communicated while the rows and the columns of the matrix are intensified. Each intensification is an event in the oddball sequence, the row and the column containing the attended cell are "rare" items and, therefore, only these events elicit a P300. The computer thus detects the transmitted character by determining which row and which column elicited the P300. We report an assessment, using a boot-strapping approach, which indicates that an off line version of the system can communicate at the rate of 7.8 characters a minute and achieve 80% accuracy. The system's performance in real time was also assessed. Our data indicate that a P300-based BCI is feasible and practical. However, these conclusions are based on tests using healthy individuals.

Comparison of high resolution EEG methods having different theoretical bases

Mathematically simulated data is used to obtain direct comparisons of the accuracies of spline/Laplacian and cortical imaging algorithms in predicting cortical potential. Even though the two approaches have quite different theoretical bases, the two methods provide nearly identical estimates of cortical activity at scales greater than about 2 or 3 cm when 64 electrodes are used.