Myasthenia gravis: an update for the clinician.

This paper provides a thorough overview of the current advances in diagnosis and therapy of myasthenia gravis (MG). Nowadays the term 'myasthenia gravis' includes heterogeneous autoimmune diseases, with a postsynaptic defect of neuromuscular transmission as the common feature. Myasthenia gravis should be classified according to the antibody specificity [acetylcholine, muscle-specific receptor tyrosine kinase (MuSK), low-density lipoprotein receptor-related protein 4 (LRP4), seronegative], thymus histology (thymitis, thymoma, atrophy), age at onset (in children; aged less than or more than 50 years) and type of course (ocular or generalized). With optimal treatment, the prognosis is good in terms of daily functions, quality of life and survival. Symptomatic treatment with acetylcholine esterase inhibition is usually combined with immunosuppression. Azathioprine still remains the first choice for long-term immunosuppressive therapy. Alternative immunosuppressive options to azathioprine include cyclosporin, cyclophosphamide, methotrexate, mycophenolate mofetil and tacrolimus. Rituximab is a promising new drug for severe generalized MG. Emerging therapy options include belimumab, eculizumab and the granulocyte- macrophage colony-stimulating factor. One pilot study on etanercept has given disappointing results. For decades, thymectomy has been performed in younger adults to improve non-paraneoplastic MG. However, controlled prospective studies on the suspected benefit of this surgical procedure are still lacking. In acute exacerbations, including myasthenic crisis, intravenous immunoglobulin, plasmapheresis and immunoadsorption are similarly effective.

Fatigue in multiple sclerosis is closely related to sleep disorders: a polysomnographic cross-sectional study.

BACKGROUND: Sleep disorders can cause tiredness. The relationship between sleep disorders and fatigue in patients with multiple sclerosis (MS) has not yet been investigated systematically. OBJECTIVE: To investigate the relationship between fatigue and sleep disorders in patients with MS. METHODS: Some 66 MS patients 20 to 66 years old were studied by overnight polysomnography. Using a cut-off point of 45 in the Modified Fatigue Impact Scale (MFIS), the entire cohort was stratified into a fatigued MS subgroup (n=26) and a non-fatigued MS subgroup (n=40). RESULTS: Of the fatigued MS patients, 96% (n=25) were suffering from a relevant sleep disorder, along with 60% of the non-fatigued MS patients (n=24) (p=0.001). Sleep-related breathing disorders were more frequent in the fatigued MS patients (27%) than in the non-fatigued MS patients (2.5%). Significantly higher MFIS values were detected in all (fatigued and non-fatigued) patients with relevant sleep disorders (mean MFIS 42.8; SD 18.3) than in patients without relevant sleep disorders (mean MFIS 20.5; SD 17.0) (p<0.001). Suffering from a sleep disorder was associated with an increased risk of fatigue in MS (odds ratio: 18.5; 95% CI 1.6-208; p=0.018). CONCLUSION: Our results demonstrate a clear and significant relationship between fatigue and sleep disorders.

[Myasthenia gravis and myasthenic syndromes]. / Myasthenia gravis und myasthene Syndrome.

Neuromuscular transmission is compromised in a variety of disorders due to immunological, toxic or congenital mechanisms. Myasthenia gravis (MG) is the most frequent among these disorders. In about 15% of cases, MG is associated with a second autoimmune disorder mainly seen in rheumatologists. Some of the drugs used in rheumatology can exacerbate MG or even trigger immunologically the occurrence of MG. In most MG patients, antibodies to the acetylcholine receptor (AChR) are present, but around 10% have AChR antibodies that are only identified by novel methods, and up to 5% have muscle-specific kinase antibodies which define a different subgroup of myasthenia. Among those MG patients with anti-AChR antibodies, a number of clinical subtypes can be identified including early-onset MG (onset

Fluoroquinolone antibiotics block neuromuscular transmission.

Fluorinated 4-quinolones are widely used antibiotics. Several case reports describe the exacerbation of muscle weakness in myasthenia gravis patients treated with fluoroquinolones. We studied the effects of norfloxacin, ofloxacin, and pefloxacin on miniature endplate potentials (MEPPs) and currents. These antibiotics progressively decreased the amplitude of the MEPPs as drug concentrations were increased from 12.5 to 100 mg/L. Fluoroquinolones should be used only with great caution in disorders that compromise the safety margin of neuromuscular transmission.

Nontraumatic spinal epidural and subdural hematomas.

Ten patients with a nontraumatic spinal extramedullary hematoma are reported, nine of the hematomas localized in the epidural space. Seven of the patients were taking anticoagulant drugs and five showed signs of liver disease, mostly due to alcoholism. The invariable first symptom was an intense local pain in the spine, followed in all but one case by radicular irradiation and in all by bladder disturbances and sensory and motor deficits of the spinal cord or cauda equina. All the patients had myelography to verify the spinal mass and were operated on as fast as possible. The outcome depended mainly on the preoperative neurologic status. If there was only an incomplete sensory and motor lesion before the operation, the patients recovered fairly well or completely. The patients who did not become capable of walking again were completely paralytic preoperatively.

Familial meningioma is not allelic to neurofibromatosis 2.

Meningiomas frequently lose parts of chromosome 22 (CHR 22), suggesting that a meningioma tumor-suppressor gene is located on CHR 22. Since meningiomas are common in neurofibromatosis 2 (NF2) and the NF2 gene is mapped to CHR 22, the NF2 gene is a candidate for the meningioma gene. To determine whether NF2 and familial meningioma are allelic mutations, we studied a family with multiple meningiomas and ependymomas in two generations using genetic linkage analysis with DNA markers known to flank the NF2 locus. Multipoint linkage analysis resulted in location scores < -2 for a region of 15 cM including the NF2 region. These results support the existence of a familial meningioma locus that is distinct from the NF2 locus.

Congenital myasthenic syndromes in two kinships with end-plate acetylcholine receptor and utrophin deficiency.

We studied two families with five affected members suffering from ptosis and slowly progressive limb-girdle muscle weakness. All patients had abnormal decremental response on low-frequency nerve stimulation, but there were no repetitive responses to single stimuli. The patients improved on anti-acetylcholinesterase drugs. Intercostal muscle was obtained for special studies from one patient of each family. In vitro microelectrode studies were done in Patient 1. Miniature end-plate potentials were of low amplitude, and the quantal content of the evoked end-plate potentials was normal. Light microscopy revealed a marked type 1 fiber predominance. Acetylcholinesterase reactivity was dispersed over increased length of individual fibers in Patient 2. On morphometry of the end-plate ultrastructure, the number of secondary synaptic clefts per neuromuscular junction and the expansion of the postsynaptic area were markedly reduced. In Patient 1, but not in Patient 2, the envelopment of the nerve terminal by Schwann cell was increased. Acetylcholine-receptor (AChR) density was reduced as judged by the reduced immunoreactivity to antibodies against different receptor subunits. Immunohistochemical analysis of proteins known to be involved in orchestrating the end-plate structure showed deficiency of the AChR-associated protein utrophin. These patients appear to have a defect in the development or maintenance of the postsynaptic clefts; whether this defect results from or causes a reduced expression of utrophin or AChR is unclear.

An autosomal-recessive congenital myasthenic syndrome with tubular aggregates in a Libyan family.

We studied a Libyan family in which five out of seven siblings have had slowly progressive limb-girdle weakness accentuated by exercise since childhood. Ptosis or ophthalmoplegia were not observed. Pronounced decremental electromyographic responses on 3 Hz stimulation indicated the presence of a defect of neuromuscular transmission. Repeated testing for acetylcholine receptor antibodies was negative. Muscle biopsy revealed tubular aggregates in 34% of the type 2 muscle fibers. Our observation illustrates the wide clinical spectrum of congenital myasthenic syndromes.

Ephedrine: effects on neuromuscular transmission.

(-)-Ephedrine has been used in the treatment of patients with myasthenia gravis. To investigate the possible effects of ephedrine on neuromuscular transmission, canine intercostal muscle endplates were studied by microelectrode techniques. At concentrations less than 10(-4) M, ephedrine had no effect on neuromuscular transmission. At a concentration of 10(-4) M, ephedrine increased the quantal content of the endplate potential by 21%. The presynaptic store of acetylcholine quanta available for immediate release was unchanged, but the probability of quantal release was increased by 16%. At this concentration, ephedrine decreased the amplitude of the miniature endplate potential by 38%. In the presence of 10(-3) M ephedrine, the miniature endplate potentials and currents became undetectable. The kinetic properties of the acetylcholine receptor channel were studied by analysis of acetylcholine-induced endplate current noise. At 10(-4) M, ephedrine reduced the channel conductance by 43% but had no effect on the open time. At 5 x 10(-4) M, ephedrine reduced the channel conductance by 84% and increased the open time by 23 percent.

Effects of the quinoline derivatives quinine, quinidine, and chloroquine on neuromuscular transmission.

The quinoline derivatives quinine, its stereoisomer quinidine, and chloroquine may worsen or provoke disorders of neuromuscular transmission. In this study, we investigate effects of these drugs on neuromuscular transmission by conventional microelectrode as well as patch-clamp techniques. At 5 x 10(-5) M, quinine, quinidine, and chloroquine reduced the quantal content of the end-plate potential by 37-45%. Between 10(-6) and 10(-4) M, all 3 drugs progressively decreased the amplitude and decay time constant of miniature end-plate potential (MEPP) and miniature end-plate current (MEPC); at 5 x 10(-3) M, the MEPP became undetectable. The effect on the MEPP was not reversed by 1 microgram/mL neostigmine. Single-channel patch-clamp analysis of the effects of quinine showed that this agent causes a long-lived open-channel as well as a closed-channel block of AChR. Tests for competitive inhibition or desensitization of the acetylcholine receptor (AChR) by quinine in concentrations that had a marked effect on the MEPC and on single-channel open and closed intervals were negative. Because quinoline drugs adversely affect both presynaptic and postsynaptic aspects of neuromuscular transmission at concentrations close to those employed in clinical practice, they should not be used, or used with caution, in disorders that compromise the safety margin of neuromuscular transmission.

Familial CNS tumors.

A family with central nervous system tumors in five individuals in two generations is reported. Of five sisters, two had an isolated meningioma and one an ependymoma. Amongst the four children of those affected there was a son with two cerebral meningiomas and a daughter with a spinal meningioma. Signs typical of von Recklinghausen neurofibromatosis (NF1) or bilateral acoustic neurofibromatosis (NF2) were not present. The pattern is consistent with autosomal dominant inheritance with relatively high penetrance.

Sporadic adult-onset distal myopathy with rimmed vacuoles, 15-18 nm tubulofilaments and extensive rod formation.

Starting after the age of 35 years this German man had a slowly progressive distal myopathy greater in the legs than in the arms. First he realized gait difficulties with reduced ankle dorsiflexion. Serum creatine kinase activity was normal. Muscle biopsy studies showed myopathic changes, rimmed vacuoles and the presence of rods in 66% of the type 1 muscle fibers. Ultrastructural examination revealed cytoplasmatic aggregates of tubulofilaments measuring 15-18 nm in diameter, myeloid bodies and rod formation. The nosological situation of this distal myopathy with tubulofilamentous inclusions is discussed.

Segmental neurofibromatosis of the sciatic nerve: case report.

A case of rare segmental neurofibromatosis is presented. Multiple neurofibromas along the right sciatic nerve were found. Other typical manifestations of neurofibromatosis were absent. By microsurgical dissection, it was possible to remove the neurofibromas from the nerve trunks and to preserve all motor and sensory functions. Classification of the different neurofibromatosis types is briefly reviewed. The problems of resection of benign major nerve trunk tumors in neurofibromatosis are discussed.

Congenital myasthenic syndrome of Brahman cattle in South Africa.

A congenital myasthenic syndrome in Brahman cattle is caused by a homozygous 20 base pair deletion (470del20) in the gene coding for the epsilon subunit of the acetylcholine receptor at the neuromuscular junction. It causes a progressive muscle weakness starting either at birth or within the first month. A PCR-based DNA test, using blood or semen stored on FTA paper, was developed and validated; the test makes it possible to differentiate rapidly and accurately between homozygous wild-type, heterozygous and homozygous affected animals. Preliminary testing of Brahman cattle in South Africa has revealed several carrier animals, some of them influential animals in the breeding population.

[Intermittent apomorphine injections as rescue therapy for advanced Parkinson's disease. Consensus statement]. / Intermittierende Apomorphin-Injektionen als Rescue-Therapie beim fortgeschrittenen M. Parkinson. Konsensusstatement.

Intermittent subcutaneous apomorphine therapy should be considered in patients with advanced Parkinson's disease who experience recurrent off periods despite optimised oral treatment (according to guidelines), for reliable and quick reversal of these otherwise refractory periods. Such treatment is also called rescue therapy. At present, apomorphine injections with the apomorphine pen are underutilised, considering its current indications and contraindications. In the present consensus statement, concepts for the use of apomorphine are presented and discussed based on existing study results, indications, and contraindications. Recommendations for a practical approach are also provided.

[Occurrence of chloroquine-induced myopathy after low-dose treatment of rheumatoid arthritis for seven years]. / Chloroquin-induzierte Myopathie. Folge einer siebenjährigen, niedrigdosierten Basistherapie bei primär-chronischer Polyarthritis.

The myotoxicity of chloroquine and hydroxychloroquine has been known for decades. Limb-girdle weakness due to a vacuolar myopathy may occur occasionally in a dose-dependent manner during the first 24 months on chloroquine. However, we report on a case in which muscular weakness developed after a daily intake of 250 chloroquine phosphate (= 155 mg chloroquine base) for a period of 7 years. Even after long-term and apparently well-tolerated chloroquine treatment, the occurrence of severe side-effects is possible.

[Congenital diseases of neuromuscular transmission: congenital myasthenia syndromes]. / Angeborene Erkrankungen der neuromuskulären Uberleitung: kongenitale myasthene Syndrome.

The congenital myasthenic syndrome constitute a group of genetic disorders affecting neuromuscular transmission. This group includes presynaptic as well as postsynaptic defects. In several congenital myasthenic syndromes, it was possible to characterize the underlying mechanism by applying modern in vitro electrophysiological methods, like single-channel recordings. These genetic disorders include defects of acetylcholine release, absence of the endplate-specific form of acetylcholinesterase, and kinetic abnormalities of the acetylcholine receptor. Recently several mutations of the acetylcholine receptor have been characterized. Clinical features of these syndromes, diagnostic work-up, and treatment are described in detail. These diseases present usually within the first 2 years of life, however, in some syndromes manifestation during adulthood is possible. The clinical spectrum ranges from mild muscle weakness to severe disability with lifethreatening episodes. Only some syndromes respond to acetylcholinesterase inhibitors. Further elucidation of these syndromes will not only lead to improved treatment, but should contribute to our understanding of synaptic transmission.