Factors directly affecting impulse transmission in inflammatory demyelinating disease: recent advances in our understanding

Gastroesophageal Reflux and Its Association With Atrial Fibrillation: A Traditional Review

Atrial fibrillation (AF) is a common arrhythmia, and gastroesophageal reflux disease (GERD) is a common gastroenterology disease; both are highly encountered daily in clinical practice. Since both share common predisposing factors, we can conclude that there is a link between them. To date, the precise mechanism of reflux disease as a possible cause of atrial fibrillation remains uncertain. However, some possibilities can be postulated, such as the inflammation process, and sympathovagal imbalance represents the main factors for how GERD can initiate AF. Vigorous aerobic exercise in healthy people can bring about acidic esophageal reflux, which is a common risk factor for AF. Various inflammatory markers such as C-reaction protein (CRP) and interleukins have been a central role in initiating AF. A large hiatal hernia (HH) can cause direct compression on the left atrium that is possibly predisposing to atrial arrhythmogenesis. It has been sporadically reported that using a proton pump inhibitor to treat GERD in patients with coexisting AF has a noticeable effect on decreasing symptoms of AF and recurrence with less cost and side effects.

Loss of Unilateral Lacrimation Following Adenoidectomy

Complications following an adenoidectomy are rare. A 13-month-old female developed unilateral lacrimation impairment following an adenoidectomy and bilateral ventilation tube insertion. The patient's post-operative course was marked by a fever, rhinorrhea, and dehydration. We suspect the impairment to be secondary to injury by suction cautery or post-operative inflammatory response and infection. Over the first nine months after surgery, the impairment spontaneously remitted.

Niclosamide Inhibits Oxaliplatin Neurotoxicity while Improving Colorectal Cancer Therapeutic Response

Neuropathic pain is a limiting factor of platinum-based chemotherapies. We sought to investigate the neuroprotective potential of niclosamide in peripheral neuropathies induced by oxaliplatin. Normal neuron-like and cancer cells were treated in vitro with oxaliplatin associated or not with an inhibitor of STAT3 and NF-κB, niclosamide. Cell production of reactive oxygen species and viability were measured by 2',7'-dichlorodihydrofluorescein diacetate and crystal violet. Peripheral neuropathies were induced in mice by oxaliplatin with or without niclosamide. Neurologic functions were assessed by behavioral and electrophysiologic tests, intraepidermal innervation, and myelination by immunohistochemical, histologic, and morphologic studies using confocal microscopy. Efficacy on tumor growth was assessed in mice grafted with CT26 colon cancer cells. In neuron-like cells, niclosamide downregulated the production of oxaliplatin-mediated H₂O₂, thereby preventing cell death. In colon cancer cells, niclosamide enhanced oxaliplatin-mediated cell death through increased H₂O₂ production. These observations were explained by inherent lower basal levels of GSH in cancer cells compared with normal and neuron-like cells. In neuropathic mice, niclosamide prevented tactile hypoesthesia and thermal hyperalgesia and abrogated membrane hyperexcitability. The teniacide also prevented intraepidermal nerve fiber density reduction and demyelination in oxaliplatin mice in this mixed form of peripheral neuropathy. Niclosamide prevents oxaliplatin-induced increased levels of IL6, TNFα, and advanced oxidized protein products. Niclosamide displayed antitumor effects while not abrogating oxaliplatin efficacy. These results indicate that niclosamide exerts its neuroprotection both in vitro and in vivo by limiting oxaliplatin-induced oxidative stress and neuroinflammation. These findings identify niclosamide as a promising therapeutic adjunct to oxaliplatin chemotherapy. Mol Cancer Ther; 16(2); 300-11. ©2016 AACR.

Motor cortex excitability and fatigue in multiple sclerosis: a transcranial magnetic stimulation study

We investigated electrophysiological correlates of fatigue in patients with multiple sclerosis (MS). Transcranial magnetic stimulation (TMS) was used to explore motor excitability in three groups of subjects: MS patients with fatigue (MS-F), MS patients without fatigue (MS-NF) and healthy control subjects. All participants had to perform a fatiguing hand-grip exercise. TMS was performed prior to and after the exercise. Prior to the motor task, MS-F patients had less inhibition in the primary motor cortex compared to both other groups. Postexercise, intracortical inhibition was still reduced in the MS-F patients compared to the MS-NF patients. In MS-F patients the postexercise time interval for normalization of the motor threshold was correlated with the fatigue severity. We conclude that MS patients with fatigue have an impairment of inhibitory circuits in their primary motor cortex. The results also indicate that fatigue severity is associated with an exercise-induced reduction of membrane excitability.

Atrial fibrillation and acid reflux disease

To date, the precise mechanism of atrial fibrillation (AF) as a possible cause of reflux disease remains uncertain, although some possibilities can be postulated. Inflammation and vagal stimulation may have a key role linking these 2 common diseases. There is some evidence in the form of case reports and limited observational studies reporting that reflux disease, and more specifically esophagitis, can cause paroxysmal AF, and various mechanisms have been proposed. Some studies have demonstrated that acid suppressive therapy by proton pump inhibitors (PPIs) may help ameliorate symptoms associated with AF and also facilitate conversion to normal sinus rhythm in a subset of patients. Further prospective studies are needed to determine if a true causal mechanism exists between the two and assess whether the mechanism is dependent on a specific subtype of AF. In addition, the response of AF-related symptoms to PPI therapy and the potential for PPI therapy to reduce the development of AF merits further investigation.

Alterations of action potentials and the localization of Nav1.6 sodium channels in spared axons after hemisection injury of the spinal cord in adult rats

Previously, we reported a pronounced reduction in transmission through surviving axons contralateral to chronic hemisection (HX) of adult rat spinal cord. To examine the cellular and molecular mechanisms responsible for this diminished transmission, we recorded intracellularly from lumbar lateral white matter axons in deeply anesthetized adult rats in vivo and measured the propagation of action potentials (APs) through rubrospinal/reticulospinal tract (RST/RtST) axons contralateral to chronic HX at T10. We found decreased excitability in these axons, manifested by an increased rheobase to trigger APs and longer latency for AP propagation passing the injury level, without significant differences in axonal resting membrane potential and input resistance. These electrophysiological changes were associated with altered spatial localization of Nav1.6 sodium channels along axons: a subset of axons contralateral to the injury exhibited a diffuse localization (>10 μm spread) of Nav1.6 channels, a pattern characteristic of demyelinated axons (Craner MJ, Newcombe J, Black JA, Hartle C, Cuzner ML, Waxman SG. Proc Natl Acad Sci USA 101: 8168-8173, 2004b). This result was substantiated by ultrastructural changes seen with electron microscopy, in which an increased number of large-caliber, demyelinated RST axons were found contralateral to the chronic HX. Therefore, an increased rheobase, pathological changes in the distribution of Nav1.6 sodium channels, and the demyelination of contralateral RST axons are likely responsible for their decreased conduction chronically after HX and thus may provide novel targets for strategies to improve function following incomplete spinal cord injury.

Neuroglia in neurodegeneration

Neuroglial cells are fundamental for control of brain homeostasis and they represent the intrinsic brain defence system. All forms in neuropathology therefore inevitably involve glia. The neurodegenerative diseases disrupt connectivity within brain circuits affecting neuronal-neuronal, neuronal-glial and glial-glial contacts. In addition neurodegenerative processes trigger universal and conserved glial reactions represented by astrogliosis and microglial activation. The complex of recently acquired knowledge allows us to regard the neurodegenerative diseases as primarily gliodegenerative processes, in which glial cells determine the progression and outcome of neuropathological process.

Cholinergic agonism alters cognitive processing and enhances brain functional connectivity in patients with multiple sclerosis

The aim of this study is to define mechanisms underlying the pharmacological effects of brain cholinesterase inhibition on cognitive function in patients with multiple sclerosis (MS). Both a Stroop task and an N-back task were used to probe the changes in brain activity using functional magnetic resonance imaging (fMRI) in a single (investigator)-blind, crossover treatment design studying 15 patients with multiple sclerosis (12 relapsing remitting, 3 secondary progressive) taking rivastigmine (4.5 mg po bid) and domperidone (10 mg po qd) or domperidone alone. Administration of rivastigmine increased Stroop functional magnetic resonance imaging activation in the right inferior frontal gyrus for the Stroop task (P < 0.05, corrected). Incremental functional magnetic resonance imaging activation with progressively greater N-back task difficulty was enhanced by rivastigmine in prefrontal and parietal cortical regions (P < 0.01, ANOVA). Functional connectivity analysis of the N-back functional magnetic resonance imaging data based on correlations between pair-wise interregional activations showed increased connectivity between left to right prefrontal, anterior cingulate to left prefrontal and right parietal to right prefrontal regions with rivastigmine (P < 0.05, corrected). Although there were no statistically significant changes in the neuropsychological task performance with rivastigmine in this small study, 11 of 15 patients showed improvements, whereas only 4 of 15 patients showed decline in performance (P = 0.07). With regard to the previous data, these findings suggest different patterns of brain response to lower dose acute and higher dose chronic administration of rivastigmine in patients with multiple sclerosis. They showed that rivastigmine enhances the prefrontal function and alters the functional connectivity associated with cognition. We interpret this as evidence for greater efficiency of brain information transfer that should increase confidence in a potentially beneficial clinical therapeutic effect.

Teriflunomide reduces behavioral, electrophysiological, and histopathological deficits in the Dark Agouti rat model of experimental autoimmune encephalomyelitis

Teriflunomide is an orally available anti-inflammatory drug that prevents T and B cell proliferation and function by inhibition of dihydroorotate dehydrogenase. It is currently being developed for the treatment of multiple sclerosis (MS). We report here for the first time the anti-inflammatory effects of teriflunomide in the Dark Agouti rat model of experimental autoimmune encephalomyelitis (EAE). Neurological evaluation demonstrated that prophylactic dosing of teriflunomide at 3 and 10 mg/kg delayed disease onset and reduced maximal and cumulative scores. Therapeutic administration of teriflunomide at doses of 3 or 10 mg/kg at disease onset significantly reduced maximal and cumulative disease scores as compared to vehicle treated rats. Dosing teriflunomide at disease remission, at 3 and 10 mg/kg, reduced the cumulative scores for the remaining course of the disease. Teriflunomide at 10 mg/kg significantly reduced inflammation, demyelination, and axonal loss when dosed prophylactically or therapeutically. In electrophysiological somatosensory evoked potential studies, therapeutic administration of teriflunomide, at the onset of disease, prevented both a decrease in waveform amplitude and an increase in the latency to waveform initiation in EAE animals compared to vehicle. Therapeutic dosing with teriflunomide at disease remission prevented a decrease in evoked potential amplitude, prevented an increase in latency, and enhanced recovery time within the CNS.

Differential effects of Th1, monocyte/macrophage and Th2 cytokine mixtures on early gene expression for molecules associated with metabolism, signaling and regulation in central nervous system mixed glial cell cultures

BACKGROUND

Cytokines secreted by immune cells and activated glia play central roles in both the pathogenesis of and protection from damage to the central nervous system (CNS) in multiple sclerosis (MS).

METHODS

We have used gene array analysis to identify the initial direct effects of cytokines on CNS glia by comparing changes in early gene expression in CNS glial cultures treated for 6 hours with cytokines typical of those secreted by Th1 and Th2 lymphocytes and monocyte/macrophages (M/M).

RESULTS

In two previous papers, we summarized effects of these cytokines on immune-related molecules, and on neural and glial related proteins, including neurotrophins, growth factors and structural proteins. In this paper, we present the effects of the cytokines on molecules involved in metabolism, signaling and regulatory mechanisms in CNS glia. Many of the changes in gene expression were similar to those seen in ischemic preconditioning and in early inflammatory lesions in experimental autoimmune encephalomyelitis (EAE), related to ion homeostasis, mitochondrial function, neurotransmission, vitamin D metabolism and a variety of transcription factors and signaling pathways. Among the most prominent changes, all three cytokine mixtures markedly downregulated the dopamine D3 receptor, while Th1 and Th2 cytokines downregulated neuropeptide Y receptor 5. An unexpected finding was the large number of changes related to lipid metabolism, including several suggesting a switch from diacylglycerol to phosphatidyl inositol mediated signaling pathways. Using QRT-PCR we validated the results for regulation of genes for iNOS, arginase and P glycoprotein/multi-drug resistance protein 1 (MDR1) seen at 6 hours with microarray.

CONCLUSION

Each of the three cytokine mixtures differentially regulated gene expression related to metabolism and signaling that may play roles in the pathogenesis of MS, most notably with regard to mitochondrial function and neurotransmitter signaling in glia.

Evaluation of Na+/K+ pump function following repetitive activity in mouse peripheral nerve

After conduction of prolonged trains of impulses the increased Na+/K+ pump activity leads to hyperpolarization. The aim of this study was to develop a mouse model to investigate the Na+/K+ pump function in peripheral nerve by measuring the decrease in excitability during activity-dependent hyperpolarization. Acute electrophysiological investigations were carried out in seven adult mice. Nerve excitability was evaluated by tracking the change in threshold current after 5 min of 100 Hz stimulation of the tibial nerve at ankle. We developed a threshold tracking system that allowed us to follow several excitability measures simultaneously from the evoked plantar compound muscle action potential (CMAP) and sciatic compound nerve action potential (CNAP). Three minutes after repetitive supramaximal stimulation maximal CMAP and CNAP amplitudes recovered but the threshold was increased approximately 40% for motor axons approximately 34% for axons generating CNAP. The threshold recovered with a rate of 3.8%/minute that was similar for nerve and motor responses. By tracking the effect of polarizing currents we found evidence of activity dependent hyperpolarization, and our data suggest that the observed threshold change after repetitive stimulation of the mouse tibial nerve is an indicator of the Na+/K+ pump function in vivo. Evaluation of activity-dependent hyperpolarization may be an important indicator of axonal ability to cope with Na+ load.

Ankyrin-G regulates inactivation gating of the neuronal sodium channel, Nav1.6

Ankyrin-G, a modular protein, plays a critical role in clustering voltage-gated sodium channels (Nav channels) in nodes of Ranvier and initial segments of mammalian neurons. However, direct effects of ankyrin-G on electrophysiological properties of Nav channels remain elusive. In this study, we explored whether ankyrin-G has a role in modifying gating properties of the neuronal Nav1.6 channel that is predominantly localized at nodes of Ranvier and initial segments. TsA201 cells transfected with the human Nav1.6 cDNA alone exhibited significant persistent sodium current (Ina-p). On the other hand, Ina-p was barely detected on co-expression with ankyrin-G. Ankyrin-B, another ankyrin, did not show such an effect. Expression of chimeras between the two isoforms of ankyrin suggests that the membrane-binding domain of ankyrin-G is critical for reducing the Ina-p of Nav1.6. These results suggest that ankyrin-G regulates neuronal excitability not only through clustering Nav channels but also by directly modifying their channel gating.

Anti-ganglioside antibodies and elevated CSF IgG levels in Guillain-Barré syndrome

Anti-ganglioside antibody production and dysfunction of blood-cerebrospinal fluid (CSF) barrier (BCB) are frequent findings in dysimmune neuropathy patients, whereas intrathecal synthesis of immunoglobulins is still a matter of debate. We examined the CSF, immunological and electrophysiological characteristics from a cohort of patients with Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyneuropathy (CIDP), and from patients with other neurological diseases as control. Thirty-eight percent of GBS patients and 28% of CIDP patients had detectable serum titers of anti-ganglioside antibodies, which were associated with a high incidence of motor conduction block and increased F wave latencies. In GBS patients, but not in CIDP or control patients, there was an association between anti-ganglioside antibodies and increased CSF immunoglobulin-G (IgG) levels as determined by the IgG index. However, none of the GBS patients had CSF oligoclonal bands (OBs) or indications of intrathecal anti-ganglioside antibody synthesis. The possibility of an abnormal CSF concentration of immunoglobulins from serum through dysfunctional BCB or damaged nerve roots, and the role of serum anti-ganglioside reactivity in this process are discussed.

Advanced Intercross Line Mapping ofEae5RevealsNcf-1andCLDN4as Candidate Genes for Experimental Autoimmune Encephalomyelitis

Eae5 in rats was originally identified in two F(2) intercrosses, (DA x BN) and (E3 x DA), displaying linkage to CNS inflammation and disease severity in experimental autoimmune encephalomyelitis (EAE), respectively. This region overlaps with an arthritis locus, Pia4, which was also identified in the (E3 x DA) cross. Two congenic strains, BN.DA-Eae5 and BN.DA-Eae5.R1, encompassing the previously described Eae5 and Pia4, were established. DA alleles within the chromosome 12 fragment conferred an increase in disease susceptibility as well as increased inflammation and demyelination in the CNS as compared with BN alleles. To enable a more precise fine mapping of EAE regulatory genes, we used a rat advanced intercross line between the EAE-susceptible DA strain and the EAE-resistant PVG.1AV1 strain. Linkage analysis performed in the advanced intercross line considerably narrowed down the myelin oligodendrocyte glycoprotein-EAE regulatory locus (Eae5) to a approximately 1.3-megabase region with a defined number of candidate genes. In this study we demonstrate a regulatory effect of Eae5 on MOG-EAE by using both congenic strains as well as fine mapping these effects to a region containing Ncf-1, a gene associated with arthritis. In addition to structural polymorphisms in Ncf-1, both sequence polymorphisms and expression differences were identified in CLDN4. CLDN4 is a tight junction protein involved in blood-brain barrier integrity. In conclusion, our data strongly suggests Ncf-1 to be a gene shared between two organ-specific inflammatory diseases with a possible contribution by CLDN4 in encephalomyelitis.

All roads lead to disconnection?--Traumatic axonal injury revisited

Traumatic brain injury (TBI) evokes widespread/diffuse axonal injury (TAI) significantly contributing to its morbidity and mortality. While classic theories suggest that traumatically injured axons are mechanically torn at the moment of injury, studies in the last two decades have not supported this premise in the majority of injured axons. Rather, current thought considers TAI a progressive process evoked by the tensile forces of injury, gradually evolving from focal axonal alteration to ultimate disconnection. Recent observations have demonstrated that traumatically induced focal axolemmal permeability leads to local influx of Ca2+ with the subsequent activation of the cysteine proteases, calpain and caspase, that then play a pivotal role in the ensuing pathogenesis of TAI via proteolytic digestion of brain spectrin, a major constituent of the subaxolemmal cytoskeletal network, the "membrane skeleton". In this pathological progression this local Ca2+ overloading with the activation of calpains also initiates mitochondrial injury that results in the release of cytochrome-c, with the activation of caspase. Both the activated calpain and caspases then participate in the degradation of the local axonal cytoskeleton causing local axonal failure and disconnection. In this review, we summarize contemporary thought on the pathogenesis of TAI, while discussing the potential diversity of pathological processes observed within various injured fiber types. The anterograde and retrograde consequences of TAI are also considered together with a discussion of various experimental therapeutic approaches capable of attenuating TAI.

Axonal pathology in subarachnoid and intracerebral hemorrhage

Electrically active axons degenerate in the presence of nitric oxide (NO) in vitro. High CSF NO concentrations have been observed in patients with hemorrhagic brain injury such as subarachnoid hemorrhage (SAH) and intracerebral hemorrhage (ICH). This study investigated the evidence for axonal injury in SAH and ICH and related this to CSF NO levels. In this study, neurofilament phosphoforms (NfH(SMI34), NfH(SMI35), NfH(SMI38), NfH(SMI310)), surrogate markers for axonal injury, and NO metabolites (nitrate, nitrite = NOx) were measured by ELISA in cerebrospinal fluid (CSF) from patients with SAH and ICH and from a group of controls. Injury severity was classified using the Glasgow Coma Scale, and survival was used as the outcome measure. Compared to the control group, a higher proportion of patients with SAH and ICH had elevated NfH(SMI34) levels from day 0 to day 6 (p < 0.001), elevated NfH(SMI35) levels from day 1 to 6 (p < 0.001), and elevated NfH(SMI310) levels at day 0, 1, 4, and 6 (p < 0.001). The NOx levels were higher in the SAH and ICH patients than in the controls (p < 0.05) and distinguished the non-survivors from the survivors (p < 0.05). No direct correlation was found for NOx with any of the NfH phosphoforms. This study provides evidence for primary and secondary axonal injury in patients with SAH and ICH, with non-survivors also having higher NOx levels. CSF NfH phosphoforms might emerge as a putative surrogate marker for monitoring the development for secondary axonal degeneration in neurocritical care and guiding targeted neuroprotective strategies.

Transforming growth factor beta 1 may regulate the stability of mature myelin sheaths

The molecular mechanisms underlying peripheral neuropathies have only been partially elucidated. In particular, the regulatory factors that control the stability and turnover of mature myelin are largely unknown. Transforming growth factor beta 1 (TGF-beta1), and its associated receptors, are expressed by mature Schwann cells. On this basis, we postulated that TGF-beta1 may be an autocrine regulator of mature myelin. This hypothesis was tested by examining the ultrastructure of myelin in adult mice that have a null mutation of their TGF-beta1 gene. We report here that the myelin of these mice is grossly abnormal. At the nodes of Ranvier, the cytoplasmic collars of the Schwann cells were expanded and the myelin had a honeycomb appearance. Focal (tomacula-like) hypermyelin structures were observed in the internodal regions of a significant number of axons in mutant nerve, and were not observed in littermate controls. Axon diameters were within the normal range and no axonal pathology was evident in mutant nerve and macrophages were absent. Results imply that lack of TGF-beta1 may have a direct effect on Schwann cells. We suggest that TGF-beta1 may stabilise compact myelin via an autocrine mechanism.

Modulation of neuronal activity by the endogenous pentapeptide QYNAD

Inflammation and demyelination both contribute to the neurological deficits characteristic of multiple sclerosis. Neurological dysfunctions are attributable to inflammatory demyelination and, in addition, to soluble factors such as nitric oxide, cytokines and antibodies. QYNAD, an endogenous pentapeptide identified in the cerebrospinal fluid of patients with demyelinating disorders, has been proposed to promote axonal dysfunction by blocking sodium channels. The present study aimed at characterizing the properties of QYNAD in acutely isolated thalamic neurons in vitro. QYNAD, but not a scrambled peptide (NYDQA), blocked sodium channels in neurons by shifting the steady-state inactivation to more negative potentials. Blocking properties followed a dose-response curve with a maximum effect at 10 microm. A fluorescently labelled QYNAD analogue with retained biological activity specifically stained thalamic neurons, positive for type II sodium channels, thus demonstrating the specificity of QYNAD binding. Our study confirms and extends previous observations describing QYNAD as a potent sodium channel-blocking agent. These data as well as our preliminary observations in in vivo experiments in an animal model of inflammatory CNS demyelination warrant further in vivo studies in order to clarify the exact pathogenetic role of QYNAD in inflammatory neurological diseases.

Reflux esophagitis in the pathogenesis of paroxysmal atrial fibrillation: results of a pilot study

BACKGROUND

We sought to assess whether proton pump inhibitor (PPI) therapy of gastroesophageal reflux disease (GERD) in patients with lone paroxysmal atrial fibrillation (PAF) leads to a reduction of PAF-related symptoms.

METHODS

The records of patients with reflux esophagitis were screened for the diagnosis of lone PAF. All patients with reflux esophagitis and lone PAF were invited for a follow-up visit, at which PAF- and GERD-related symptoms, medication, and electrocardiogram were recorded.

RESULTS

Among 89 patients, 18 (6 women, aged 39-69 years) had lone PAF. Decrease or disappearance of at least one PAF-related symptom occurred in 14 of 18 patients (78%) after PPI therapy. In two of the remaining four patients, GERD-related symptoms persisted. Antiarrhythmic drugs were discontinued in five patients, and none had to be increased in dosage or newly prescribed. The electrocardiogram showed sinus rhythm in all patients.

CONCLUSION

In lone PAF, GERD should be investigated as a potential pathogenetic mechanism. PPI therapy reduces not only GERD-related but also PAF-related symptoms.

Axonal injury in multiple sclerosis

The pivotal role of axons in the pathophysiology and pathogenesis of multiple sclerosis (MS) is increasingly becoming the focus of our attention. Axonal injury, considered at one time to be a late phenomenon, is now recognized as an early occurrence in the inflammatory lesions of MS. There is converging evidence from histopathologic, as well as magnetic resonance imaging and magnetic resonance spectroscopy studies, that axons play a crucial and dynamic role during the evolution of MS pathology and the development of clinical disability. It has been repeatedly demonstrated that neurologic functional impairment correlates best with axonal, rather than myelin, injury. The pathophysiology of axonal injury remains speculative. Although generally considered to be sequelae of demyelination, it is possible that axonal injury in MS is indeed a primary event. The discovery that axonal injury can be reversible has provided an impetus to institute early therapy. The finding that irreversible axonal transection occurs in early lesions has underscored now, more than ever before, the need to curtail inflammation and the need to institute early treatment with disease-modifying agents. The axon will undoubtedly remain the focus of our attention regarding research on MS now and in the future.

Demyelination and axonal loss in multifocal motor neuropathy: distribution and relation to weakness

Multifocal motor neuropathy (MMN) is characterized by a slowly progressive, asymmetric weakness of the limbs without sensory loss. The arms are usually affected to a greater extent than the legs, and distal muscles more than proximal muscles. The distribution of electrophysiological abnormalities and its correlation with weak muscle groups in MMN have not been investigated systematically. The aim of the present study was to assess whether electrophysiological abnormalities have a preferential or random distribution, whether electrophysiological abnormalities in a nerve correlate with weakness in the innervated muscles, and whether these results are relevant for the development of optimal electrodiagnostic protocols. We compared the pattern of weakness and electrophysiological abnormalities in 39 patients with a lower motoneuron syndrome and a positive response to intravenous immunoglobulins. All patients underwent an extensive standardized electrophysiological examination. Electrophysiological evidence of demyelination was found more often in the nerves of the arms and was distributed randomly over lower arm, upper arm and shoulder segments. Electrophysiological evidence of axonal loss presented more frequently in longer nerves, occurring most often in the leg nerves. For the arm nerves, it is possible that the length dependence of axonal loss is due to the random distribution of demyelinating lesions that lead to axonal degeneration. Weakness was associated with features of demyelination and axonal loss in the nerves of the arm, and with features of axonal loss in leg nerves. However, a substantial number (approximately one-third) of electrophysiological abnormalities were found in nerves innervating non-weakened muscles. These results imply that in MMN, conduction block is most likely to be found in long arm nerves innervating weakened muscles, but if conduction block cannot be detected in these nerves, the electrophysiological examination should be extended to other arm nerves including those innervating non-weakened muscles.

Nitric oxide inhibition of mitochondrial respiration and its role in cell death

Nitric oxide (NO) or its derivatives (reactive nitrogen species, RNS) inhibit mitochondrial respiration in two different ways: (i) an acute, potent, and reversible inhibition of cytochrome oxidase by NO in competition with oxygen; and, (ii) irreversible inhibition of multiple sites by RNS. NO inhibition of respiration may impinge on cell death in several ways. Inhibition of respiration can cause necrosis and inhibit apoptosis due to ATP depletion, if glycolysis is also inhibited or is insufficient to compensate. Inhibition of neuronal respiration can result in excitotoxic death of neurons due to induced release of glutamate and activation of NMDA-type glutamate receptors. Inhibition of respiration may cause apoptosis in some cells, while inhibiting apoptosis in other cells, by mechanisms that are not clear. However, NO can induce (and inhibit) cell death by a variety of mechanisms unrelated to respiratory inhibition.

Paroxysmal kinesigenic choreoathetosis because of cryptogenic myelitis. Remission with carbamazepine and the pathogenetic role of altered sodium channels

Lesions of the spinal cord causing paroxysmal kinesigenic choreoathetosis are rare and most of the reported cases have been because of multiple sclerosis. We now describe this movement disorder occurring in a patient who developed a myelitis of unknown aetiology. A typically striking remission followed treatment with carbamazepine. It is suggested that the effect of the drug and the disorder itself may both be explained on the basis of altered sodium channels.