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We report a recent case of the severe congenital variant of glycogen storage disease type IV with prolonged survival. The patient was found to be a compound heterozygote for two novel mutations, a missense mutation in exon 5 (p.H188P, c.563A>C) and a severe mutation in intron 5 (c.691+2T>C). We propose that the genotype and the quality of medical care may account for the severe but non-lethal phenotype.

Mutations of mitochondrial genome are responsible for respiratory chain defects in numerous patients. We have used a strategy, based on the use of a mismatch-specific DNA endonuclease named " Surveyor Nuclease", for screening the entire mtDNA in a group of 50 patients with neuromuscular features, suggesting a respiratory chain dysfunction. We identified mtDNA mutations in 20% of patients (10/50). Among the identified mutations, four are not found in any mitochondrial database and have not been reported previously. We also confirm that mtDNA polymorphisms are frequently found in a heteroplasmic state (15 different polymorphisms were identified among which five were novel).

The authors analyzed muscle biopsy specimens of 104 patients with creatine kinase activity greater than 500 UI/L (normal 10 to 170 UI/L) without signs of muscle weakness. They achieved a definite or probable diagnosis in 55% of cases. The most frequently identified diseases were glycogen storage diseases, muscular dystrophies, and inflammatory myopathies. The probability of making a diagnosis was higher in children and when creatine kinase level was greater than 2,000 UI/L.

Electron microscopy has a strategic position in the diagnosis of neuromuscular disorders. In muscular fibers, the main abnormalities include vacuoles, inclusion bodies, and myofibrillar disorganization with or without abnormal inclusion material. Vacuolar changes include lipidic and glycogenic storage vacuoles, rimmed vacuoles, and lysosomal and autophagic vacuoles. Accumulation of abnormal inclusion material is found in nemaline myopathy, actinopathies, and hyaline body myopathy. Myofibrillar disorganization involves cores, multiminicores, and myosin chain depletion. Myofibrillar myopathies associate a pathologic pattern of myofibrillar dissolution and ectopic protein expression. They can be divided into two groups: myofibrillar myopathies with multiple expression proteins and myofibrillar myopathies with desmin and alphaB-crystallin expression only. In these two conditions, electron microscopy shows accumulation of a granulofilamentous material immunoreactive for desmin. At least three genes are implicated: desmin, alphaB-crystallin, and myotilin. Lastly, electron microscopy serves to identify changes, pathogenic or not, which are not shown up by light microscopy. Moreover, electron microscopy gives insight on pathophysiological mechanisms and can guide molecular genetics analysis.

Introduction: The aim of the study was to describe patterns of neuromuscular weakness using a combination of electromyography and histology, and to evaluate functional outcome in patients following complicated cardiovascular surgery., Methods: Fifteen adults requiring long-term mechanical ventilation (>15 days) following cardiovascular surgery associated with postoperative complications were prospectively included. Electrophysiological and histological analyses (muscle and nerve) were performed when failure to wean from mechanical ventilation associated with peripheral neuromuscular weakness was noticed. Functional disability was evaluated 12 months after surgery., Results: Six patients had a predominantly axonal neuropathy, six presented with myopathy, and three patients had a combination of axonal neuropathy and myopathy. All of them presented with acute tetraparesis and failure to wean from mechanical ventilation. All of the study patients who received corticosteroids exhibited a myopathic pattern (with or without axonopathic changes) but never an axonopathic pattern only. Only two of the eight survivors at 12 months were not ambulatory. These two patients had no detectable compound muscle action potential on electrophysiological examination., Conclusion: The combination of electromyographic evaluation and neuromuscular histological abnormalities could help to identify the type and severity of neuromuscular weakness, in turn helping to evaluate the patient's potential functional prognosis.

Neuromuscular diseases with eosinophilia include a number of disorders associated with variable degrees of muscle, peripheral nerve, and connective tissue involvement. Eosinophilic infiltration in blood and/or tissue is a consistent finding. In addition to the neurologic manifestations of systemic vascularitis, in particular Churg and Strauss syndrome, there are three main forms of neuromuscular disease. Diffuse fasciitis or Shulman syndrome which can be limited to the fascia or associated with perimyositis is sensitive to corticosteroids. Eosinophilic myositis corresponds to focal muscle involvement and is also sensitive to corticosteroids. Eosinophilic polymyositis is a manifestation of essential hypereosinophilic syndrome and is life-threatening. Eosinophilia-myalgia syndrome and toxic oil syndrome are separate entities that occur in outbreaks and involve poisoning by ingestion of L-tryptophan and adulterated oil containing aniline respectively. The key to diagnosis of these neuromuscular diseases is muscle biopsy to detect the presence of polynuclear eosinophils.

We report three cases of patients who complained of myalgia showing histological features similar to tubular aggregates in their muscle biopsies. All had an elevated erythrocyte sedimentation rate without any evidence of infectious or autoimmune disease. On electron microscopy, small areas of myofibrillar degeneration, selectively in type II fibres, were found in all patients, but no tubular aggregates were seen. Although the pathogenesis of these lesions is unclear, it does seem that this condition is acquired and transient.

The pathological findings in 165 patients explored for malignant hyperthermia (MH) susceptibility are reported. The first group of 120 subjects were patients investigated for MH. These patients had suffered an attack of MH under anaesthetic or were members of families in which a subject had died of MH. In vitro contracture tests revealed 25 malignant hyperthermia susceptible (MHS) subjects, with positive contracture tests for halothane and caffeine, 5 malignant hyperthermia subjects with reaction to caffeine only (MHC), 3 malignant hyperthermia subjects with reaction to halothane only (MHH) and 87 malignant hyperthermia negative (MHN) subjects with normal contracture tests. The second group of 45 subjects had exertional heat stroke. In vitro contracture tests performed at least 3 months after the exertional heat stroke revealed 11 MHS, 6 MHC, 2 MHH subjects and 26 MHN. In both groups, whatever the in vitro contracture test results, pathological findings were heterogeneous and revealed various changes: rhabdomyolysis, mitochondrial myopathy, denervation, type II atrophy, AMPase deficiency, non-specific findings or normal features. Central core myopathy was only observed in the first subgroup and was the only disease significantly associated with MH. In contrast to previous reports, this study demonstrates the absence of a specific malignant hyperthermia or exertional heat stroke myopathy. Furthermore, the discovery of MHS subjects among the EHS group of patients highlights the need for systematic exploration of all these patients.

A retrospective study of 40 patients with various neuromuscular disorders and more than 3 muscle fibers with rimmed vacuoles has been performed. Two subgroups of patients were distinguished according to the presence or absence of inflammatory exudates. In the first group (14 patients), inflammatory exudates were observed and numerous fibers showed partial invasion. Abnormal filamentous inclusions (16-18 nm in diameter) were found by electron microscopy in muscle fibers cytoplasm and/or nuclei. The diagnosis of inclusion body myositis (IBM) was made in these cases. They presented with insidious proximal muscle weakness and were not improved by immunosuppressive therapy. Immunohistological studies demonstrated T lymphocytes predominance, only few natural killer and B lymphocytes. The number of T8 lymphocytes was high in endomysial sites while T4 were more numerous in perivascular exudates. Abnormal membranous expression of class I MHC antigens was observed on muscle fibers lying near the inflammatory exudates. In the second group of cases (26 patients), no inflammatory exudate was observed. This group of neuromuscular diseases with rimmed vacuoles was heterogeneous. In 10 cases, abnormal filamentous inclusions (16-18 nm in diameter) were observed in rimmed vacuoles. However, this ultrastructural feature did not help in distinguishing subgroups. Various neuromuscular disorders were observed in this group: oculopharyngeal muscular dystrophy (12 cases with IBM like filaments in 4 cases), chronic spinal atrophy (5 cases with IBM like filaments in 3 cases), post poliomyelitis syndrome (2 cases with IBM-like filaments in one), muscle glycogenosis with IBM like filaments (2 cases), hereditary limb girdle myopathy or distal myopathy (3 cases) and 1 patient clinically presenting with polymyositis and another with cramps and myalgias. No abnormal sarcolemmal expression of class I MHC was found in this group. The pathogenesis of IBM is discussed. Besides T cell mediated cytotoxicity, denervation may be involved. The nature of the abnormal 16-18 nm filamentous inclusions remains unknown. These filaments are not IBM specific.

We describe a young man with a progressive neurological disorder including myoclonus, mental retardation, muscle weakness and a mitochondrial myopathy (myoclonus epilepsy and ragged red fibres--MERRF). Multiple abnormalities of the mitochondrial respiratory chain in skeletal muscle are shown by direct measurement of the flux through the individual complexes, low-temperature redox spectroscopy and decreased immunodetectable subunits of complexes I and IV by immunoblotting. No abnormality of mitochondrial DNA was found. This is the first report of combined defects of complexes I, III and IV as a cause of this clinical syndrome. However, we propose that the occurrence of multiple respiratory chain defects may be more common than previously recognised and that this particular combination of defects, involving complexes I, III and IV, may be the predominant biochemical abnormality in MERRF.

We report severe deficiency of complex II of the mitochondrial respiratory chain and low activities of complex I and II in skeletal muscle mitochondria from a young woman with progressive muscle weakness and encephalopathy. Defects of complex II have only very rarely been described and this is the first report of decreased immunoreactive subunits associated with severe deficiency of this enzyme.

CT Scan examination in 145 cases of neuromuscular diseases yielded the following results: Diagnosis between myogenic and neurogenic process is inconstant and cannot be considered as absolute. In myogenic diseases the X ray density of muscle is early decreased with a preservation of muscle outline. In neurogenic diseases muscle volume is early decreased. Coexistence of atrophic and hypertrophic muscles indicates primarily muscle disease. Some patterns of involvement appear to be frequent. In Duchenne's dystrophy a contrast exists between atrophic "empty" or hypertrophic muscles during the ambulatory period and "ghostly" muscles during the terminal period. In facio-scapulo-humeral muscular dystrophy, tibialis anterior and hamstring muscles have often a decreased density and psoas muscles are normal or hypertrophic. In myotonic dystrophy a hypodense perifemoral crescent is frequently observed. Diagnosis between limb-girdle myopathy ("empty" muscles with preserved limits, hypertrophic muscles, hypodense gastrocnemius medialis muscles) and chronic spinal amyotrophy (irregular and atrophic muscles without selective involvement and hypertrophic muscles) is tentatively proposed but is not considered to be clear-cut. Muscle involvement has an asymmetric distribution in amyotrophic lateral sclerosis and is rather symmetric in peripheral neuropathies.

Two cases of quadriceps amyotrophy, probably of chronic neurogenic origin are reported. Only the knee jerks were diminished, the calves hypertrophic, and the serum creatine kinase level very high in one case, and there were neurogenic electromyographic abnormalities in the quadriceps. In the first case, biopsy of the quadriceps muscle revealed a neurogenic origin with hyalinized hypertrophic fibres. CT scan showed abnormalities not only in the quadriceps but also in the sartorius, gracilis and gastrocnemius muscles. A second biopsy specimen from the gastrocnemius muscle showed histological findings similar to those of the quadriceps. In the second case, the EMG and biopsy findings suggested a myogenic origin, but 6 years later they were compatible with neurogenic atrophy. Differentiation from Becker dystrophy is very difficult in the first case and the second case is more a focal spinal amyotrophy. Further, in spite of their localization, the extension of the affected muscles changes the diagnosis. The same applies to chronic quadriceps amyotrophy in general, which cannot be regarded as an entity, but which suggests muscular dystrophy, spinal atrophy, polymyositis or a metabolic disorder. These cases can be compared with the four cases reported in the literature, which were regarded as a "forme fruste" of chronic spinal amyotrophy.