Peripheral axotomy of motoneurons triggers Wallerian degeneration of injured axons distal to the lesion, followed by axon regeneration. Centrally, axotomy induces loss of synapses (synaptic stripping) from the surface of lesioned motoneurons in the spinal cord. At the lesion site, reactive Schwann cells provide trophic support and guidance for outgrowing axons. The mechanisms of synaptic stripping remain elusive, but reactive astrocytes and microglia appear to be important in this process. We studied axonal regeneration and synaptic stripping of motoneurons after a sciatic nerve lesion in mice lacking the intermediate filament (nanofilament) proteins glial fibrillary acidic protein (GFAP) and vimentin, which are upregulated in reactive astrocytes and Schwann cells. Seven days after sciatic nerve transection, ultrastructural analysis of synaptic density on the somata of injured motoneurons revealed more remaining boutons covering injured somata in GFAP(-/-)Vim(-/-) mice. After sciatic nerve crush in GFAP(-/-)Vim(-/-) mice, the fraction of reinnervated motor endplates on muscle fibers of the gastrocnemius muscle was reduced 13 days after the injury, and axonal regeneration and functional recovery were delayed but complete. Thus, the absence of GFAP and vimentin in glial cells does not seem to affect the outcome after peripheral motoneuron injury but may have an important effect on the response dynamics.
Complement proteins C1q and C3 play a critical role in synaptic elimination during development. Axotomy of spinal motoneurons triggers removal of synaptic terminals from the cell surface of motoneurons by largely unknown mechanisms. We therefore hypothesized that the complement system is involved also in synaptic stripping of injured motoneurons. In the sciatic motor pool of wild type (WT) mice, the immunoreactivity (IR) for both C1q and C3 was increased after sciatic nerve transection (SNT). Mice deficient in C3 (C3(-/-)) showed a reduced loss of synaptic terminals from injured motoneurons at one week after SNT, as assessed by immunoreactivity for synaptic markers and electron microscopy. In particular, the removal of putative inhibitory terminals, immunopositive for vesicular inhibitory amino acid transporter (VIAAT) and ultrastructurally identified as type F synapses, was reduced in C3(-/-) mice. In contrast, lesion-induced removal of nerve terminals in C1q(-/-) mice appeared similar to WT mice. Growth associated protein (GAP)-43 mRNA expression in lesioned motoneurons increased much more in C3(-/-) compared to WT mice after SNT. After sciatic nerve crush (SNC), the C3(-/-) mice showed a faster functional recovery, assessed as grip strength, compared to WT mice. No differences were detected regarding nerve inflammation at the site of injury or pattern of muscle reinnervation. These data indicate that a non-classical pathway of complement activation is involved in axotomy-induced adult synapse removal, and that its inhibition promotes functional recovery.
Synapse elimination in the adult central nervous system can be modelled by axotomy of spinal motoneurons which triggers removal of synapses from the cell surface of lesioned motoneurons by processes that remain elusive. Proposed candidate mechanisms are removal of synapses by reactive microglia and astrocytes, based on the remarkable activation of these cell types in the vicinity of motoneurons following axon lesion, and/or decreased expression of synaptic adhesion molecules in lesioned motoneurons. In the present study, we investigated glia activation and adhesion molecule expression in motoneurons in two mouse strains with deviant patterns of synapse elimination following axotomy. Mice deficient in complement protein C3 display a markedly reduced loss of synapses from axotomized motoneurons, whereas mice with impaired function of major histocompatibility complex (MHC) class Ia display an augmented degree of stripping after axotomy. Activation of microglia and astrocytes was assessed by semiquantative immunohistochemistry for Iba 1 (microglia) and GFAP (astrocytes), while expression of synaptic adhesion molecules was determined by in situ hybridization. In spite of the fact that the two mouse strains display very different degrees of synapse elimination, no differences in terms of glial activation or in the downregulation of the studied adhesion molecules (SynCAM1, neuroligin-2,-3 and netrin G-2 ligand) could be detected. We conclude that neither glia activation nor downregulation of synaptic adhesion molecules are correlated to the different extent of the synaptic stripping in the two studied strains. Instead the magnitude of the stripping event is most likely a consequence of a precise molecular signaling, which at least in part is mediated by immune molecules.
The diagnostic algorithm of computerized tomography (CT) and lumbar puncture (LP) for suspected subarachnoid haemorrhage (SAH) has lately been challenged by the advancement of radiological techniques, such as higher resolution offered by newer generation CT-scanners and increased availability of CT-angiography. A purely radiological workup of suspected SAH offers great advantages for both patients and the health care system, but the risks of abandoning LP in this setting are not well investigated. We have characterized the differential diagnostic yield of LP in the investigation of suspected SAH by a retrospective study. From the hospital laboratory database, we analyzed the medical records of all patients who had undergone CSF-analysis in search of subarachnoid bleeding during 2009-2011. A total of 453 patients were included. In 14 patients (3 %) the LP resulted in an alternative diagnosis, the most common being aseptic meningitis. Two patients (0.5 %) received treatment for herpes meningitis. Five patients (1 %) with subarachnoid haemorrhages were identified. Among these, the four patients presenting with thunderclap headache had non-aneurysmal bleedings and did not require surgical intervention. We conclude that the differential diagnostic yield of LP in investigation of suspected SAH is low, which indicates that alternative diagnoses is not a reason to keep LP in the workup when a purely radiological strategy has been validated. However, algorithms should be developed to increase the recognition of aseptic meningitis. One hundred and fifty-three patients (34 %) were admitted to undergo LP, which estimates the number of hospital beds that might be made available by a radiological diagnostic algorithm.
Purpose: Few studies have been dedicated to assess neurological symptoms in relations to hypoglycemia. In this study we investigated the association between different levels of hypoglycemia and the occurrence of epileptic seizures in patients without a prior diagnosis of epilepsy. Method: A retrospective cross-sectional study. Results: We identified 388 individuals from a laboratory database in Swedish regional hospital who had been found to have a glucose value of <= 3.5 mM between January and December 2009. Medical records were reviewed. Hypoglycemia was defined at three different categories: 0-2 mM (40 patients), 2.1-3 mM (154 patients) and 3.1-3.5 mM (194 patients). 14 patients had disturbance of consciousness including 3 with seizures. The majority of cases had coma, a generalized tonic-clonic seizure was seen only when s-glucose dropped below 2.0 mM. Two cases with focal seizure were noted, one at s-glucose 2.0 mM, and one at s-glucose 3.3 mM. The absolute risks (95% confidence interval) for having major neurological symptoms at glucose levels of <= 2.0 mM were 0.25 (0.13-0.41), 0.02 (0-0.06) at 2.1-3.0 mM and 0.01 (0-0.03) at 3.1-3.5 mM. Conclusion: Coma is the most common neurological symptom related to hypoglycemia. Epileptic seizures are rare and not as common as previously assumed.
The successful outcome of peripheral neuronal regeneration is attributed both to the growth permissive milieu and the intrinsic ability of the neuron to initiate appropriate cellular responses such as changes in gene expression and cytoskeletal rearrangements. Even though numerous studies have shown the importance of interactions between the neuron and the extracellular matrix (ECM) in axonal outgrowth, the molecular mechanisms underlying the contact between ECM receptors and the cellular cytoskeleton remain largely unknown. Unconventional myosins constitute an important group of cytoskeletal-associated motor proteins. One member of this family is the recently described myosin-X. This protein interacts with several members of the axon growth-associated ECM receptor family of integrins and could therefore be important in neuronal outgrowth. In this study, using radioactive in situ hybridization, we found that expression of myosin-X mRNA is upregulated in adult rat sensory neurons and spinal motoneurons after peripheral nerve injury, but not after central injury. Thus, myosin-X was upregulated after injuries that can-be followed by axonal regeneration. We also found that the protein is localized to neuronal growth cones and that silencing of myosin-X using RNA interference impairs the integrin-mediated growth of neurites on laminin, but has no effect on non-integrin mediated growth on N-cadherin.
Status epilepticus (SE) is a dreaded neurological emergency. A reignited interest in SE has resulted in a more adaptive use of treatment protocols. More knowledge on SE of various aetiologies is therefore needed. We are interested in treatment of SE under hyponatremia, and have here evaluated whether SE induced by systemic kainic acid could be a suitable platform for such studies. Acute hyponatremia was induced in C57/BL6 mice by intraperitoneal injection of dDAVP and water loading. Hyponatremic mice displayed an increased frequency of epileptiform spikes on EEG and 5/9 hyponatremic mice displayed electrographic seizures. After kainic acid (20mg/kg) treatment, hyponatremic mice displayed significantly longer time with electrographic seizure activity, which was also seen after treatment with diazepam (20mg/kg). We conclude that hyponatremia augments kainic acid-induced SE, This model might be a valuable platform for studies on treatment of SE in hyponatremia.
Background: The role of new antiepileptic drugs (AED) in the treatment of status epilepticus (SE) is of interest, especially in benzodiazepine-resistant status epilepticus where phenytoin is deemed inappropriate due to allergy or comorbidity. Levetiracetam (LEV) is a new AED with few side effects. It is easy to administer. Reports exist of its use in SE in adults.
Aims: To clarify the evidence for use of LEV as an alternative stage two AED in treatment of SE by a systematic review of the literature.
Method: An online MEDLINE search identified 118 articles. The abstracts were screened for studies written in English, in which (1) at least two adults had been treated, and (2) LEV had been administered intravenously as the first AED, on its own or together with benzodiazepines. Ten studies were included.
Results: Out of the ten studies, seven were retrospective observational, two prospective observational, and one prospective randomized. The studies described a total of 334 patients. The most common reason for administrating LEV was that standard treatment was deemed inappropriate. The efficacy ranged from 44% to 94%, with higher efficacy reported in the retrospective studies.
Conclusions: The evidence for use of LEV as an alternative stage two AED in SE is limited. The higher efficacy reported in retrospective studies indicates possible publication bias, and caution is advised when the results of these retrospective studies are considered in clinical decision-making.
Introduction: Recently, several epidemiological studies have demonstrated that epilepsy develops after approximately 10% of all cerebrovascular lesions. With an aging population, poststroke epilepsy is likely to be of increasing relevance to neurologists and more knowledge on the condition is needed. Patients with poststroke epilepsy are likely to differ from other epilepsy patient populations regarding age, side-effect tolerability, comorbidities, and life expectancy, all of which are important aspects when counselling newly diagnosed patients to make informed treatment decisions. Method: We have here performed a nested case-control study on 36 patients with poststroke epilepsy and 55 controls that suffered stroke but did not develop epilepsy. The average follow-up time was between 3 and 4 years. Results: In our material, two-thirds of patients achieved seizure freedom and 25% experienced a prolonged seizure (status epilepticus) during the follow-up period. Cases consumed more health care following their stroke, but did not suffer more traumatic injuries. Interestingly, the mortality among cases and controls did not differ significantly. This observation needs to be confirmed in larger prospective studies, but indicate that poststroke epilepsy might not infer additional mortality in this patient group with considerable comorbidities. Conclusions: The observations presented can be of value in the counselling of patients, reducing the psychosocial impact of the diagnosis, and planning of future research on poststroke epilepsy.
The expanding number of disease-causing dysfunctions of synaptic proteins illustrates the importance of investigating newly discovered proteins involved in neuronal transmission. The gene Slc10A4 encodes a recently described carrier protein present in pre-synaptic terminals of cholinergic and monoaminergic neurons. The biological significance of this recently described transporter protein is currently unknown. We here investigated whether absence of the Slc10a4 protein has any impact on function of the cholinergic system. We first investigated the sensitivity of Slc10a4 null mice to cholinergic stimulus in vitro. In contrast to wild type mice, gamma oscillations occurred spontaneously in hippocampal slices from Slc10a4 null mice. Furthermore, moderate treatment of Slc10a4 null slices with the cholinergic agonist carbachol induced epileptiform activity. In vivo, 3-channel EEG measurements in freely behaving mice revealed that Slc10a4 null mice had frequent epileptiform spike-activity before treatment, and developed epileptic seizures, detected by EEG and accompanied by observable behavioral components, more rapidly after injection of the cholinergic agonist pilocarpine. Similar results were obtained on non-operated mice, as evaluated by behavioral seizures and post mortem c-Fos immunohistochemistry. Importantly, Slc10a4 null mice and wild type control mice were equally sensitive to the glutamatergic chemoconvulsant kainic acid, demonstrating that absence of Slc10a4 led to a selective cholinergic hypersensitivity. In summary, we report that absence of the recently discovered synaptic vesicle protein Slc10a4 results in increased sensitivity to cholinergic stimulation.
Purpose: Status epilepticus (SE) has attracted renewed interest lately, and efforts are made to optimize every treatment stage. For refractory SE, optimal supporting care involves mechanical ventilation and intensive care unit (ICU) admission. Infections often complicate SE and recently a single-centre observational study demonstrated an association between infections and poor short-term outcome of SE in a cohort of severely ill patients. We have here attempted to replicate those findings in a different cohort. Method: We performed a retrospective observational study and included all patients with a diagnosis of SE during 2008-2012 at a Swedish tertiary referral centre. Results: The cohort consisted of 103 patients (53% female, 47% male, median age 62 years, range 19-87 years). In house mortality was less than 2 and 70% of the patients' were discharged home. The most common aetiologies of SE were uncontrolled epilepsy (37%) and brain tumours (16%). A total of 39 patients suffered infections during their stay. Presence of infection was associated with mechanical ventilation (OR 3.344, 95% Cl 1.44-7.79) as well as not being discharged home (OR2.705, 95% Cl 1.14-6.44), and duration of SE was significantly longer in patients with infection (median 1 day vs. 2.5 days, p < 0.001). Conclusion: We conclude that the previously described association between infections, a longer SE duration, and an unfavourable outcome of SE seems valid also in SE of less severe aetiology.