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In the present work, a tuned quantum dot / ring system under both external magnetic and electric fields is studied. The energy eigenvalues and wave functions are analytically derived. Then, an analytical expression for the Stark shift is obtained. The results reveal that: (i) The ground state and excited state energies at large and small electric fields show various behaviours, (ii) the ground and excited state energies reduce by raising the electric field and (iii) the ground and excited state energies increase by enhancing the system size. Our model can be transformed into a two-dimensional (2D) quantum disk or a 2D quantum ring. The results show that the Stark shifts at low and high electric fields vary. The behaviour depends strongly on the magnetic field and the system size. [ABSTRACT FROM AUTHOR]

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune neuromuscular disorder affecting the presynaptic neuromuscular junction. LEMS is considered to be a rare disease, but its clinical recognition and diagnosis are important due to its high association with underlying lung cancer which may be detected at the very early stages. The onset is insidious and its clinical features are subtle which add to the further delay of diagnosis, between months to years., (Copyright (c) 2009 S. Karger AG, Basel.)

The inflammatory myopathies are a heterogeneous group of immune-mediated myopathies that present as pure form or in association with other autoimmune diseases or malignancy. Although they share few similarities in their clinical presentations and pathophysiologic aspects, for the most part they are different and distinctive. The 3 major subsets are: dermatomyositis (DM), polymyositis (PM), and sporadic inclusion body myositis (S-IBM).This review highlights our understanding of these disorders, their clinical aspects, diagnosis, pathogenesis, and treatment.

Background: Behçet disease is a vasculitis with mucocutaneous, ocular, arthritic, vascular, and other manifestations. Its neurologic manifestations (neuro-Behçet disease) are relatively rare, but they must be thoroughly investigated due to their grave prognosis., Review Summary: The frequency of neurologic manifestations, more common in male Behçet patients, is between 5% and 30%. Both the central and peripheral nervous systems can be involved. Central nervous system manifestations can be divided into 2 main groups: (1) parenchymal involvement, which includes brainstem involvement, hemispheric manifestations, spinal cord lesions, and meningoencephalitic presentations; (2) nonparenchymal involvement, including dural sinus thrombosis, arterial occlusion, and/or aneurysms. Peripheral neuropathy and myopathy are relatively rare. Cerebrospinal fluid analysis reveals pleocytosis and elevated protein levels. Magnetic resonance imaging is the investigation of choice which often reveals iso-/hypointense lesions in T1-weighted images and hyperintense lesions in T2-weighted images, mostly in the mesodiencephalic junction, cerebellar peduncles, and other parts of the brainstem. Corticosteroids and adjuvant immunosuppressive therapy are used for parenchymal manifestations, and corticosteroids and anticoagulants are used for treatment of dural sinus thrombosis., Conclusion: Neuro-Behçet disease must be considered in the differential diagnosis of stroke in young adults, multiple sclerosis, movement disorders, intracranial hypertension, intracranial sinovenous occlusive diseases, and other neurologic syndromes.

Recent advances in neuroimmunology have led to improvements in the pathogenesis, diagnosis, prognosis, and treatment of many neuromuscular disorders. The value of autoantibody testing is increasing steadily in neurologic practice. Not all antibodies have a high yield in diagnosis. In some disorders, such as generalized adult onset of myasthenia gravis, Lambert-Eaton myasthenic syndrome,Miller Fisher syndrome, and multifocal motor neuropathy,autoantibody tests provide accurate diagnosis and can be considered biologic markers of these disorders.

Stretch of nerve has been reported to decrease the amplitude of the compound action potential (CAP) with a complete block appearing in approximately 30 minutes. But for the most part, those experiments were carried out in vivo, and it is generally accepted that the failure of responses was due to a closure of vessels supplying the nerve with a resulting ischemia and anoxia. These studies were undertaken to determine if stretch of nerve has effects that are independent of interference with its vascular supply. In the studies, lengths of rat sciatic and dog peroneal nerves were removed and placed in a chamber supplied with oxygen in which their CAPs were continuously elicited and recorded. This in vitro preparation obviated interference with the nerve's metabolism on stretching. We have previously shown that the form change termed 'beading,' appearing within 10 seconds and reversing as quickly on relaxation, can be elicited with tensions of only several grams. We wished to determine if stretch adequate to produce beading could alter CAPs with the same rapidity. Tensions below 2 g had little effect. On applying tensions of 10-100 g, levels well above those needed to bead the fibers, both increases and decreases of CAP amplitude were seen. The changes occurred within 10 seconds of stretch application, the time at which beading arises with stretch. Although the decreases of CAP amplitudes could be accounted for by beading, the degree of CAP change did not correspond to the amount of tension applied. We hypothesize that the constrictions in the beaded fibers increase axial resistivity and diminish local currents so as to block conduction. The lack of an increasing degree of decreased CAP amplitude with increases in tension is ascribed to the inhibition of elongation offered by the collagen fibrils present in nerve. Collagenase applied to nerves allowed a further increase in length, producing a 'hyperbeading,' showing much longer lengths of beading constrictions on stretch. This would further increase axial resistance and is taken to account for the greater decreases of CAP amplitudes seen following collagenase treatment. To account for those cases where increases of CAP amplitude were seen on stretch, we hypothesize that stretch can also cause an increase in the excitability of the nodes. The outcome of stretch in any given nerve would be the resultant of two opposing actions; beading of the internodes causes a decrease of local currents leading to block of CAPs, while an increased excitability of the nodes acts to augment the responses.

This article briefly reviews the initial approach to the patient suspected of having metabolic myopathy. Diagnostic highlights include relevant points of history, physical examination, blood work-up, forearm ischemic exercise test, electrophysiologic testings and muscle biopsy. The diagnostic evaluation is discussed in detail in separate articles.

This article provides a review of some of the muscular disorders that can arise from some of the commonly seen endocrinologic disturbances. Thyroid, parathyroid, and adrenal dysfunctions as they relate to neuromuscular symptoms are discussed. Common clinical presentations of the endocrine myopathies are highlighted, along with diagnostic evaluation and treatments.

Domiciliary assisted ventilation has been used to prolong life in patients with neuromuscular diseases. Although earlier studies suggest that the majority of patients are satisfied with their lives, the physician's perception of a patient's poor quality of life on assisted ventilation is a major reason for discouraging assisted ventilation. In this study, the quality of life was assessed in 19 patients with neuromuscular diseases on domiciliary tracheal intermittent positive-pressure ventilation for a mean duration of 54 months. An attempt was made to compare the quality of life of Duchenne muscular dystrophy patients with that of amyotrophic lateral sclerosis patients. More than two-thirds of patients were satisfied with their lives. Eighty-four percent thought they had made the right choice. Patients with amyotrophic lateral sclerosis were somewhat more negative or ambiguous toward assisted ventilation and had lower life satisfaction scores as compared with Duchenne muscular dystrophy patients. Financial stresses were significant. Assisted ventilation should be offered as a viable option to patients with neuromuscular diseases. Larger studies may be useful in influencing insurance companies to make expenses associated with assisted ventilation reimbursable.

The complementarity-determining regions (CDRs) of a human kappa light chain were replaced with CDRs from a murine gamma-1 heavy chain and, by use of molecular modeling, key heavy chain framework residues were identified and thus included to preserve the native conformation of the heavy chain CDRs. Co-expression of this hybrid human kappa chain (V[HB]C[L]) with a human kappa chain counterpart (V[L]C[L], engineered to contain murine light chain CDRs) resulted in the secretion of high levels of a heterodimeric protein (V[HB]C[L]::V[L]C[L]) termed 'kappabody'. This protein also had equivalent affinity for antigen as the Fab' of the parent murine IgG1. High-level secretion was also observed for the hybrid chain as homodimers (V[HB]C[L]::V[HB]C[L]), which is not observed for chimeric chains consisting of a heavy chain variable region and light chain constant region, i.e. V[H]C[L] homodimers or single chains are not secreted. This indicates that regions within the variable domain, required for secretion of light chains, reside outside of the hypervariable regions (CDRs) and that the heavy chain CDRs and supporting residues do not prevent secretion. These results demonstrate the possibility of designing small, single-domain molecules possessing a given binding activity which may be secreted at high levels from mammalian cells.

Nerve fibers which appear beaded (varicose, spindle-shaped, etc.) are often considered the result of pathology, or a preparation artifact. However, beading can be promptly elicited in fresh normal nerve by a mild stretch and revealed by fast-freezing and freeze-substitution, or by aldehyde fixating at a temperature near 0 degree C (cold-fixation). The key change in beading are the constrictions, wherein the axon is much reduced in diameter. Axoplasmic fluid and soluble components are shifted from the constrictions into the expansions leaving behind compacted microtubules and neurofilaments. Labeled cytoskeletal proteins carried down by slow axonal transport are seen to move with the soluble components and not to have been incorporated into and remain with, the cytoskeletal organelles on beading the fibers. Lipids and other components of the myelin sheath are also shifted from the constrictions into the expansions, with preservation of its fine structure and thickness. Additionally, myelin intrusions into the axons are produced and a localized bulging into the axon termed "leafing". The beading constrictions do not arise from the myelin sheath: beading occurs in the axons of unmyelinated fibers. It does not depend on the axonal cytoskeleton: exposure of nerves in vitro to beta, beta'-iminodipropionitrile (IDPN) disaggregates the cytoskeletal organelles and even augments beading. The hypothesis advanced was that the beading constrictions are due to the membrane skeleton; the subaxolemmal network comprised of spectrin/fodrin, actin, ankyrin, integrins and other transmembrane proteins. The mechanism can be activated directly by neurotoxins, metabolic changes, and by an interruption of axoplasmic transport producing Wallerian degeneration.

The most common form of diabetic neuropathy is chronic, distal symmetrical sensorimotor, or predominantly sensory neuropathy; the latter is invariably associated with some degree of autonomic dysfunction. There are, however, other neuropathic patterns in diabetes mellitus that are uncommon but are important to recognize, since they may mimic many other non-neurologic diseases. This article discusses a variety of forms of mononeuropathies and diabetic proximal motor neuropathy, commonly known as diabetic amyotropy.

Toxic myopathies may occur with a variety of prescribed medications, illicit drug abuse, or other toxins. The article discusses an overview of some of the compounds that may cause myopathy, the clinical and laboratory features, histology, mechanisms of action, and potential risk factors of myopathy. The ability to recognize these syndromes is essential to avoid unnecessary tests and to avoid delay in treatment, especially in critically ill patients or patients with other neuromuscular diseases.

Adult-onset myasthenia gravis is an acquired autoimmune disorder of neuromuscular transmission in which acetylcholine receptor antibodies attack the postsynaptic membrane of the neuromuscular junction. Although the cause of this disease is unknown, the role of immune responses in its pathogenesis is well established. Circulating acetylcholine receptor antibodies are present in 80% to 90% of patients with the generalized form of myasthenia gravis. Most patients have ptosis, diplopia, dysarthria and dysphagia. The weakness and fatigue worsen on exertion and improve with rest. Respiratory muscle and limb weakness are rare at the onset of the disease. For the past two decades, there has been considerable progress in understanding the diagnosis and management of myasthenia gravis. The diagnosis is based on clinical presentation, neurologic examination, and confirmation by means of electrophysiologic testing and immunologic studies. Myasthenia gravis mimics many neuromuscular diseases and even illnesses such as depression and chronic fatigue syndrome. One should always exclude drug-induced myasthenia gravis for all patients. With the introduction of new modalities of treatment, particularly immunosuppressive or immunomodulating drugs, plasma exchange and thymectomy, the morbidity and mortality of myasthenia gravis have decreased dramatically to the point that myasthenia gravis should not be considered as serious a disease as it once was. Although the several therapeutic options are usually effective and have meant independence in daily life to many patients with myasthenia gravis, well-designed, controlled, prospective studies are still lacking.

With increasing survival rates from acute medical or surgical emergencies a new form of peripheral neuropathy, CIP, has been recognized. CIP can be seen only in patients who are considered to be critically ill; therefore, it invariably occurs in the ICU. Typically, initial symptoms begin with transient (hours to a few days) septic encephalopathy followed by generalized weakness, manifested in weaning failure, limb weakness and hyporeflexia. Diagnosis is confirmed by an EMG. CIP should be considered in any elderly patient with sepsis and prolonged respiratory muscle weakness. Prognosis is poor in severe cases, in which the EMG also shows severe axonal degeneration. In milder forms, fair to good recovery is expected within weeks. Management includes treatment of sepsis, normalization of failing organ function, physical therapy and proper nutrition.

A 44-year-old man suffered a severe anoxic encephalopathy with rapid fatal outcome. His EEG prior to expiration showed a burst-suppression pattern (BSP) with occurrence of two previously unreported clinical features: spontaneous chewing movements during the burst and tonic posturing during the suppression phase. In coma the appearance of BSP in the EEG commonly implies a severe anoxic/metabolic insult to the brain with a grave prognosis. The pattern is considered to be interictal, except in cases presenting with myoclonic status epilepticus. Subtle intermittent movements of the eye, mouth and cardiovascular rhythm are uncommon and it is unclear whether these are epileptic events or not. This case indicates that the suppression phase can also have associated clinical signs.

Forty-two EEG recordings with bilateral generalized slow background activity, but asymmetric because of suppression of the amplitude over one hemisphere, were selected for the study. This pattern was prospectively correlated with neurological findings as well as neuroimaging techniques. In 76% of cases, the suppression of the amplitude could be lateralized correctly to the site of cerebral insult. It is suggested that: (a) unilateral attenuation of the amplitude of the background EEG correlates highly with ipsilateral focal cerebral acute or subacute large lesion; (b) in cases where bihemispheric slow activity is present, the hemisphere with the lower amplitude is likely to be the site of such a structural lesion; and (c) this study also supports a previous report that amplitude depression has the same pathophysiological significance in EEG as delta activity.

A thirty-six year old male with a sixteen month history of a progressive neurological disorder had Behcet's disease. His initial electroencephalogram showed periodic lateralizing epileptiform discharges (PLEDs). The electroencephalographic changes in this disorder have not been described in detail in the American literature. The review of world publications in this matter disclosed that there is no specific EEG pattern in this condition, and that electroencephalographic changes are mainly related to the side of the lesion and have no prognostic value.