Implications of starting antiepileptic treatment prior to electroencephalography in first epileptic seizures

INTRODUCTION

This study aimed to determine whether the administration of antiepileptic drugs (AED) alters the likelihood of detecting epileptiform abnormalities in electroencephalographies (EEG) performed early after a first epileptic seizure.

METHODS

We performed a retrospective, observational study including patients with a first seizure attended at our centre's emergency department between July 2014 and November 2019. We collected clinical data, as well as technical data on the acquisition and interpretation of the EEG performed within the first 72 hours after the seizure, and the factors related with seizure recurrence.

RESULTS

We recruited 155 patients with a mean (SD) age of 48.6 (22.5) years; 61.3% were men. Regarding seizure type, 51% presented tonic-clonic seizures of unknown onset and 12% presented focal to bilateral tonic-clonic seizures. Thirty-nine patients (25.2%) received AED treatment before the EEG was performed: 33 received a non-benzodiazepine AED and 6 received a benzodiazepine. Epileptiform abnormalities were observed in 29.7% of patients. Previous administration of AEDs was not significantly associated with the probability of detecting interictal epileptiform abnormalities (P = .25) or with the risk of recurrence within 6 months (P = .63).

CONCLUSIONS

Administration of AEDs before an early EEG following a first seizure does not decrease the likelihood of detecting epileptiform abnormalities. These findings suggest that starting AED treatment immediately in patients with a high risk of early recurrence does not imply a reduction in the diagnostic accuracy of the test.

HIGH PREVALENCE OF PARASPINAL MUSCLE INVOLVEMENT IN ADULTS WITH McARDLE DISEASE

INTRODUCTION/AIMS

Very few studies analyzing the pattern of muscle involvement in magnetic resonance imaging (MRI) of patients with McArdle disease have been reported to date. We aimed to examine the pattern of muscle fat replacement in patients with McArdle disease.

METHODS

We performed a retrospective study including all patients with genetically confirmed McArdle disease followed in our center from January 2010 to March 2021. Clinical data were collected from the medical record. Whole-body MRI was performed as part of the diagnostic evaluation. The distribution of muscle fat replacement and its severity were analyzed.

RESULTS

Nine patients were included. Median age at onset was 7 years (range:5-58) and median age at the time when MRI was performed was 57.3 years (range 37.2-72.8). At physical examination 4 patients had permanent weakness: in 3 the weakness was limited to paraspinal muscles whereas in one the weakness involved the paraspinal and proximal upper limb muscles. Muscle MRI showed abnormalities in 6 of the 7 studied patients. In all of them fat replacement of paravertebral muscles was found. Other muscles frequently affected were the tongue in 3, subscapularis in 3, and long head of biceps femoris and semimembranosus in 2.

DISCUSSION

Our findings suggest that paraspinal muscle involvement is common in McArdle disease and support the need to include this disease in the differential diagnosis of the causes of paraspinal muscle weakness. Involvement of the tongue and subscapularis are also frequent in McArdle disease. This article is protected by copyright. All rights reserved.

Implications of initiating antiseizure drugs prior to the performance of EEG in first epileptic seizures

INTRODUCTION

This study aimed to determine whether the administration of antiepileptic drugs (AED) alters the likelihood of detecting epileptiform abnormalities in electroencephalographies (EEG) performed early after a first epileptic seizure.

METHOD

We performed a retrospective, observational study including patients with a first seizure attended at our centre's emergency department between July 2014 and November 2019. We collected clinical data, as well as technical data on the acquisition and interpretation of the EEG performed within the first 72hours after the seizure, and the factors related with seizure recurrence.

RESULTS

We recruited 155 patients with a mean (SD) age of 48.6 (22.5) years; 61.3% were men. Regarding seizure type, 51% presented tonic-clonic seizures of unknown onset and 12% presented focal to bilateral tonic-clonic seizures. Thirty-nine patients (25.2%) received AED treatment before the EEG was performed: 33 received a non-benzodiazepine AED and 6 received a benzodiazepine. Epileptiform abnormalities were observed in 29.7% of patients. Previous administration of AEDs was not significantly associated with the probability of detecting interictal epileptiform abnormalities (P=.25) or with the risk of recurrence within 6 months (P=.63).

CONCLUSIONS

Administration of AEDs before an early EEG following a first seizure does not decrease the likelihood of detecting epileptiform abnormalities. These findings suggest that starting AED treatment immediately in patients with a high risk of early recurrence does not imply a reduction in the diagnostic accuracy of the test.

How soon should urgent EEG be performed following a first epileptic seizure?

PURPOSE

Patients with a first unprovoked epileptic seizure are often seen in emergency services. Electroencephalography (EEG) is indicated for diagnosing epilepsy, but the optimal time to perform this test has not been defined. This study aimed to determine the time interval following a seizure within which EEG has the greatest diagnostic yield.

METHODS

We conducted a retrospective study of all adult patients with a first unprovoked seizure who had undergone emergency EEG (July 2014-December 2019). Data collection included demographics, seizure type, time interval to EEG study, EEG pattern identified, and the prescription after emergency assessment. An optimal cut-off point for time to EEG was obtained, and an adjusted regression model was performed to establish associations with the presence of epileptiform abnormalities.

RESULTS

A total of 170 patients were included (mean age: 50.7 years, 40.6% women). Epileptiform discharges were identified in 34.1% of recordings, nonepileptiform abnormalities in 46.5%, and normal findings in 19.4%. A lower latency from seizure to EEG was associated with a higher probability of finding epileptiform discharges (median: 12.7 in the epileptiform EEGs vs. 20 h in the nonepileptiform EEGs, p < 0.001). The time interval associated with the highest probability of detecting an epileptiform EEG pattern was within the first 16 h after seizure onset: 52.1% of recordings performed before the 16-h cut-off showed these abnormal patterns compared with 20.2% performed after (p < 0.001). These findings were not related to the presence of an epileptogenic lesion in neuroimaging or to other clinical variables. The finding of epileptiform abnormalities was followed by a greater prescription of antiseizure drugs (96.4% vs. 66% in nonepileptiform patterns, p < 0.001).

CONCLUSION

The diagnostic yield of EEG following a first unprovoked epileptic seizure is highest when this test is performed within the first 16 h after onset of the event.

Heterozygous CAPN3 missense variants causing autosomal-dominant calpainopathy in seven unrelated families

AIMS

Recessive variants in CAPN3 gene are the cause of the commonest form of autosomal recessive limb girdle muscle dystrophy. However, two distinct in-frame deletions in CAPN3 (NM_000070.3:c.643_663del21 and c.598_621del15) and more recently, Gly445Arg and Arg572Pro substitutions have been linked to autosomal dominant (AD) forms of calpainopathy. We report 21 affected individuals from seven unrelated families presenting with an autosomal dominant form of muscular dystrophy associated with five different heterozygous missense variants in CAPN.

METHODS

We have used massively parallel gene sequencing (MPS) to determine the genetic basis of a dominant form of limb girdle muscular dystrophy in affected individuals from seven unrelated families.

RESULTS

The c.700G> A, [p.(Gly234Arg)], c.1327T> C [p.(Ser443Pro], c.1333G> A [p.(Gly445Arg)], c.1661A> C [p.(Tyr554Ser)] and c.1706T> C [p.(Phe569Ser)] CAPN3 variants were identified. Affected individuals presented in young adulthood with progressive proximal and axial weakness, waddling walking and scapular winging or with isolated hyperCKaemia. Muscle imaging showed fatty replacement of paraspinal muscles, variable degrees of involvement of the gluteal muscles, and the posterior compartment of the thigh and minor changes at the mid-leg level. Muscle biopsies revealed mild myopathic changes. Western blot analysis revealed a clear reduction in calpain 3 in skeletal muscle relative to controls. Protein modelling of these variants on the predicted structure of calpain 3 revealed that all variants are located in proximity to the calmodulin-binding site and are predicted to interfere with proteolytic activation.

CONCLUSIONS

We expand the genotypic spectrum of CAPN3-associated muscular dystrophy due to autosomal dominant missense variants.

Non-compaction cardiomyopathy and early respiratory failure in an adult symptomatic female carrier of centronuclear myopathy caused by a MTM1 mutation

X-linked myotubular myopathy (XLMTM) is a rare neuromuscular condition caused by mutations in the MTM1 gene. Female carriers are believed to be usually asymptomatic; nevertheless, recent reports have displayed a wide a spectrum of clinical involvement in females suggesting that MTM1 mutations might be underestimated in this population. Here we report a 55-year-old woman manifesting with an abrupt respiratory decline, whose respiratory function tests revealed a severe restrictive ventilatory defect. The neurological examination identified mild proximal leg weakness and her cardiac evaluation showed a non-compaction cardiomyopathy with normal left ventricle function. Muscle biopsy was consistent with centronuclear myopathy. Next-generation sequencing of 49 genes related to congenital myopathies allowed the identification of a 4 bp deletion in the MTM1 gene, leading to a truncating mutation previously described in males but for the first time reported in a female patient.

Ryanodine receptor type 3 (RYR3) as a novel gene associated with a myopathy with nemaline bodies

BACKGROUND AND PURPOSE

Nemaline myopathy (NEM) has been associated with mutations in 12 genes to date. However, for some patients diagnosed with NEM, definitive mutations are not identified in the known genes, suggesting that there are other genes involved. This study describes compound heterozygosity for rare variants in ryanodine receptor type 3 (RYR3) gene in one such patient.

METHODS AND RESULTS

Clinical examination of the patient at 22 years of age revealed a long narrow face, high arched palate and bilateral facial weakness. She had proximal weakness in all four limbs, mild scapular winging but no scoliosis. Muscle biopsy revealed wide variation in fibre size with type 1 fibre predominance and atrophy. Abundant nemaline bodies were located in perinuclear and subsarcolemmal areas, and within the cytoplasm. No likely pathogenic mutations in known NEM genes were identified. Copy number variation in known NEM genes was excluded by NEM-targeted comparative genomic hybridization array. Next-generation sequencing revealed compound heterozygous missense variants in the RYR3 gene. RYR3 transcripts are expressed in human fetal and adult skeletal muscle as well as in human brain and cauda equina samples. Immunofluorescence of human skeletal muscle revealed a 'single-row' appearance of RYR3, interspersed between the 'double rows' of ryanodine receptor type 1 (RYR1) at each A-I junction.

CONCLUSION

The results suggest that variants in RYR3 may cause a recessive muscle disease with pathological features including nemaline bodies. We characterize the expression pattern of RYR3 in human skeletal muscle and brain, and the subcellular localization of RYR1 and RYR3 in human skeletal muscle.

Molecular characterization of congenital myasthenic syndromes in Spain

Congenital myasthenic syndromes (CMS) are a heterogeneous group of genetic disorders, all of which impair neuromuscular transmission. Epidemiological data and frequencies of gene mutations are scarce in the literature. Here we describe the molecular genetic and clinical findings of sixty-four genetically confirmed CMS patients from Spain. Thirty-six mutations in the CHRNE, RAPSN, COLQ, GFPT1, DOK7, CHRNG, GMPPB, CHAT, CHRNA1, and CHRNB1 genes were identified in our patients, with five of them not reported so far. These data provide an overview on the relative frequencies of the different CMS subtypes in a large Spanish population. CHRNE mutations are the most common cause of CMS in Spain, accounting for 27% of the total. The second most common are RAPSN mutations. We found a higher rate of GFPT1 mutations in comparison with other populations. Remarkably, several founder mutations made a large contribution to CMS in Spain: RAPSN c.264C > A (p.Asn88Lys), CHRNE c.130insG (Glu44Glyfs*3), CHRNE c.1353insG (p.Asn542Gluf*4), DOK7 c.1124_1127dup (p.Ala378Serfs*30), and particularly frequent in Spain in comparison with other populations, COLQ c.1289A > C (p.Tyr430Ser). Furthermore, we describe phenotypes and distinguishing clinical signs associated with the various CMS genes which might help to identify specific CMS subtypes to guide diagnosis and management.

Differential proteomic analysis of abnormal intramyoplasmic aggregates in desminopathy

Desminopathy is a subtype of myofibrillar myopathy caused by desmin mutations and characterized by protein aggregates accumulating in muscle fibers. The aim of this study was to assess the protein composition of these aggregates. Aggregates and intact myofiber sections were obtained from skeletal muscle biopsies of five desminopathy patients by laser microdissection and analyzed by a label-free spectral count-based proteomic approach. We identified 397 proteins with 22 showing significantly higher spectral indices in aggregates (ratio >1.8, p<0.05). Fifteen of these proteins not previously reported as specific aggregate components provide new insights regarding pathomechanisms of desminopathy. Results of proteomic analysis were supported by immunolocalization studies and parallel reaction monitoring. Three mutant desmin variants were detected directly on the protein level as components of the aggregates, suggesting their direct involvement in aggregate-formation and demonstrating for the first time that proteomic analysis can be used for direct identification of a disease-causing mutation in myofibrillar myopathy. Comparison of the proteomic results in desminopathy with our previous analysis of aggregate composition in filaminopathy, another myofibrillar myopathy subtype, allows to determine subtype-specific proteomic profile that facilitates identification of the specific disorder.

BIOLOGICAL SIGNIFICANCE

Our proteomic analysis provides essential new insights in the composition of pathological protein aggregates in skeletal muscle fibers of desminopathy patients. The results contribute to a better understanding of pathomechanisms in myofibrillar myopathies and provide the basis for hypothesis-driven studies. The detection of specific proteomic profiles in different myofibrillar myopathy subtypes indicates that proteomic analysis may become a useful tool in differential diagnosis of protein aggregate myopathies.

Isolated cardiomyopathy caused by a DMD nonsense mutation in somatic mosaicism: genetic normalization in skeletal muscle

X-linked dilated cardiomyopathy is a pure cardiac dystrophinopathy phenotype mainly caused by DMD mutations that present a specific transcription effect in cardiac tissue. We report a 26-year-old male who presented with severe dilated cardiomyopathy and high creatine kinase. The patient did not complain of skeletal muscle weakness. A muscle biopsy showed mild dystrophic changes and a low proportion of dystrophin-negative fibres. A molecular study identified a nonsense DMD mutation (p.Arg2098X) in somatic mosaicism. The ratio of mutant versus normal allele in blood and skeletal muscle suggests selective pressure against mutant muscle cells, a process known as genetic normalization. We hypothesize that this process may have mitigated skeletal muscle symptoms in this patient. This is the second report of a DMD somatic mosaic with evidence of genetic normalization in muscle. Somatic DMD mutations should be considered in patients presenting with idiopathic dilated cardiomyopathy.

Distinct muscle imaging patterns in myofibrillar myopathies

OBJECTIVE

To compare muscle imaging findings in different subtypes of myofibrillar myopathies (MFM) in order to identify characteristic patterns of muscle alterations that may be helpful to separate these genetic heterogeneous muscular disorders.

METHODS

Muscle imaging and clinical findings of 46 patients with MFM were evaluated (19 desminopathy, 12 myotilinopathy, 11 filaminopathy, 1 alphaB-crystallinopathy, and 3 ZASPopathy). The data were collected retrospectively in 43 patients and prospectively in 3 patients.

RESULTS

In patients with desminopathy, the semitendinosus was at least equally affected as the biceps femoris, and the peroneal muscles were never less involved than the tibialis anterior (sensitivity of these imaging criteria to detect desminopathy in our cohort 100%, specificity 95%). In most of the patients with myotilinopathy, the adductor magnus showed more alterations than the gracilis muscle, and the sartorius was at least equally affected as the semitendinosus (sensitivity 90%, specificity 93%). In filaminopathy, the biceps femoris and semitendinosus were at least equally affected as the sartorius muscle, and the medial gastrocnemius was more affected than the lateral gastrocnemius. The semimembranosus mostly showed more alterations than the adductor magnus (sensitivity 88%, specificity 96%). Early adult onset and cardiac involvement was most often associated with desminopathy. In patients with filaminopathy, muscle weakness typically beginning in the 5th decade of life was mostly pronounced proximally, while late adult onset (>50 years) with distal weakness was more often present in myotilinopathy.

CONCLUSIONS

Muscle imaging in combination with clinical data may be helpful for separation of distinct myofibrillar myopathy subtypes and in scheduling of genetic analysis.

Distinct muscle imaging patterns in myofibrillar myopathies

OBJECTIVE

To compare muscle imaging findings in different subtypes of myofibrillar myopathies (MFM) in order to identify characteristic patterns of muscle alterations that may be helpful to separate these genetic heterogeneous muscular disorders.

METHODS

Muscle imaging and clinical findings of 46 patients with MFM were evaluated (19 desminopathy, 12 myotilinopathy, 11 filaminopathy, 1 alphaB-crystallinopathy, and 3 ZASPopathy). The data were collected retrospectively in 43 patients and prospectively in 3 patients.

RESULTS

In patients with desminopathy, the semitendinosus was at least equally affected as the biceps femoris, and the peroneal muscles were never less involved than the tibialis anterior (sensitivity of these imaging criteria to detect desminopathy in our cohort 100%, specificity 95%). In most of the patients with myotilinopathy, the adductor magnus showed more alterations than the gracilis muscle, and the sartorius was at least equally affected as the semitendinosus (sensitivity 90%, specificity 93%). In filaminopathy, the biceps femoris and semitendinosus were at least equally affected as the sartorius muscle, and the medial gastrocnemius was more affected than the lateral gastrocnemius. The semimembranosus mostly showed more alterations than the adductor magnus (sensitivity 88%, specificity 96%). Early adult onset and cardiac involvement was most often associated with desminopathy. In patients with filaminopathy, muscle weakness typically beginning in the 5th decade of life was mostly pronounced proximally, while late adult onset (>50 years) with distal weakness was more often present in myotilinopathy.

CONCLUSIONS

Muscle imaging in combination with clinical data may be helpful for separation of distinct myofibrillar myopathy subtypes and in scheduling of genetic analysis.

Expression of mutant ubiquitin (UBB+1) and p62 in myotilinopathies and desminopathies

Protein aggregates in muscle cells are the morphological hallmark of myofibrillar myopathies, including myotilinopathies and desminopathies. The aim of the present study is to analyse the expression of mutant ubiquitin (UBB+1), an aberrant form of ubiquitin which accumulates in certain disorders characterized by intracellular aggregates of proteins, and p62, a multimeric signal protein which plays an active role in aggregate formation, in muscle biopsies from patients suffering from myotilinopathy and desminopathy in order to gain understanding of the mechanisms leading to protein aggregation in these disorders. Single immunohistochemistry, and single- and double-labelling immunofluorescence and confocal microscopy for UBB+1 and p62, has been performed in muscle biopsies from patients suffering from myotilinopathy and desminopathy. Strong UBB+1 immunoreactivity, colocalizing with myotilin aggregates, was found in muscle fibres in myotilinopathies. UBB+1 accumulation, colocalizing with desmin aggregates, also occurs in desminopathies. In addition, strong p62 immunoreactivity colocalizing with myotilin aggregates was observed in myotilinopathies. Similarly, p62 immunoreactivity colocalizing with desmin aggregates was found in desminopathies. The present findings suggest that accumulation of protein aggregates in myotilinopathies and in desminopathies may be related with UBB+1/abnormal protein complexes which are resistant to proteasome degradation. Furthermore, these observations suggest a relationship between the presence of p62 and the formation of inclusions in different subtypes of myofibrillar myopathies.

[Outcomes of surgical treatment in 100 patients with arteriovenous malformations of the brain]

AIM

To conduct a descriptive analysis of a series of patients with arteriovenous malformations (AVM) that had been treated surgically.

PATIENTS AND METHODS

Of a total of 189 adult patients with AVM evaluated consecutively in our hospital, 100 patients who had undergone surgical treatment were selected; a number of demographic, clinical and radiological aspects were then analysed, together with data concerning any associated vascular lesions, the type of surgical treatment, angiographic results and clinical outcomes.

RESULTS

The mean age was 34 years (range: 15-71 years). The most common presenting symptom was intracranial haemorrhage, which occurred in 60 cases (60%). The AVM were located in the supratentorial convexity in 79% of cases, 8% were deep and 13% were situated in the cerebellum. The most frequent degree, according to the Spetzler and Martin scale, was grade III. Seventeen patients had other associated lesions and it should be noted that eight patients had aneurysms. Most of the patients (78%) underwent elective surgery and, in two cases, post-embolisation. Surgical treatment (salvage surgery) was performed in 13 patients (13%) when other therapeutic options failed and seven patients were submitted to emergency operations because of brain haemorrhages. The postoperative angiographic study showed complete removal of the AVM in 98% of cases. The clinical outcomes were as follows: 75%, good recovery; 20%, moderate incapacity; and 5%, an important degree of incapacity.

CONCLUSION

Surgery is the best therapeutic option for patients with AVM, if they are selected in an appropriate manner.

NARP-MILS syndrome caused by 8993 T>G mitochondrial DNA mutation: a clinical, genetic and neuropathological study

The 8993 T>G mutation in mitochondrial DNA has been associated with variable syndromes of differing severity ranging from maternally inherited Leigh's syndrome (MILS) to neuropathy, ataxia, retinitis pigmentosa (NARP), depending on the mutation loads in affected patients. We report a kindred with several members in the same generation suffering NARP or Leigh's syndrome due to a 8993 T>G mutation. Post-mortem studies of the brain in one affected member clinically presenting with a neurological disorder intermediate between adult Leigh's syndrome and NARP showed symmetrical lesions of the basal ganglia and brainstem closely resembling those usually described in typical Leigh's syndrome. Analysis of mtDNA in different tissues showed a high proportion of mutant genome in brainstem, cerebral cortex, putamen, cerebellum and thalamus. These observations illustrate the continuum of clinical and neuropathological manifestations associated with the 8993 T>G mutation of the mtDNA.

Involvement of clusterin and the aggresome in abnormal protein deposits in myofibrillar myopathies and inclusion body myositis

Myofibrillar myopathies (MM) are characterized morphologically by the presence of non-hyaline structures corresponding to foci of dissolution of myofibrils, and hyaline lesions composed of aggregates of compacted and degraded myofibrillar elements. Inclusion body myositis (IBM) is characterized by the presence of rimmed vacuoles, eosinophilic inclusions in the cytoplasm, rare intranuclear inclusions, and by the accumulation of several abnormal proteins. Recent studies have demonstrated impaired proteasomal expression and activity in MM and IBM, thus accounting, in part, for the abnormal protein accumulation in these diseases. The present study examines other factors involved in protein aggregation in MM and IBM. Clusterin is a multiple-function protein which participates in Abeta-amyloid, PrP(res) and a-synuclein aggregation in Alzheimer disease, prionopathies and a-synucleinopathies, respectively. gamma-Tubulin is present in the centrosome and is an intracellular marker of the aggresome. Moderate or strong clusterin immunoreactivity has been found in association with abnormal protein deposits, as revealed by immunohistochemistry, single and double-labeling immunofluorescence and confocal microscopy, in MM and IBM, and in target structures in denervation atrophy. Gamma-Tubulin has also been observed in association with abnormal protein deposits in MM, IBM, and in target fibers in denervation atrophy. These morphological findings are accompanied by increased expression of clusterin and gamma-tubulin in muscle homogenates of MM and IBM cases, as revealed by gel electrophoresis and Western blots. Together, these observations demonstrate involvement of clusterin in protein aggregates, and increased expression of aggresome markers in association with abnormal protein inclusions in MM and IBM and in targets, as crucial events related to the pathogenesis of abnormal protein accumulation and degradation in these muscular diseases.

Connexin 31 (GJB3) is expressed in the peripheral and auditory nerves and causes neuropathy and hearing impairment

Mutations in the connexin 31 (GJB3) gene have been found in subjects with dominant and recessive deafness and in patients with erythrokeratodermia variabilis. We report here a dominant mutation in the GJB3 gene (D66del) in a family affected with peripheral neuropathy and sensorineural hearing impairment. A wide range of disease severity for peripheral neuropathy, from asymptomatic cases to subjects with chronic skin ulcers in their feet and osteomyelitis leading to amputations, was detected in D66del patients. Mild, often asymmetrical, hearing impairment was found in all but one patient with mutation D66del of this family and the same mutation was present in an independent family ascertained because of hearing impairment. We have found mouse connexin 31 (Gjb3) gene expression in the cochlea and in the auditory and sciatic nerves, showing a pattern similar to that of Gjb1 (connexin 32), of which the human ortholog (GJB1) is involved in X-linked peripheral neuropathy. This expression pattern, together with auditory-evoked brainstem anomalous response in D66del patients, indicates that hearing impairment due to GJB3 mutations involves alterations in both the cochlea and the auditory nerve. Peripheral neuropathy is the third phenotypic alteration linked to GJB3 mutations, which enlarges the list of genes that cause this group of heterogeneous disorders.

Bcl-2 and bax immunohistochemistry in denervation-reinnervation and necrosis-regeneration of rat skeletal muscles

Bcl-2 and Bax immunohistochemistry was examined in the skeletal muscle of rats after cutting the sciatic nerve, as a model of denervation and reinnervation, and in the anterior tibialis muscle of rats after an intramuscular injection of metoclopramide, as a model of necrosis and regeneration of muscle fibers, to better understand the role of these proteins in muscle disorders. An increase in Bax immunoreactivity was seen in long-standing denervated and reinnervated muscle fibers. Bcl-2 and Bax immunoreactivity was limited to macrophages in necrotic muscle fibers at 24 h after the intramuscular injection of metoclopramide. However, increased Bax immunoreactivity was observed in regenerating muscle fibers by the fourth day after the injection. Muscle fiber nuclei with the morphological features of apoptosis were not observed in rat muscles after the intramuscular injection of metoclopramide or after the severing of the sciatic nerve. Furthermore, using the Tunel method, no stained nuclei were observed in the two groups of animals. Our observations in the experimental models of skeletal muscle denervation-reinnervation and necrosis-regeneration here described suggest that modification in the intensity of the Bax protein is not related to the process of cell death but rather that increased Bax expression is associated with muscle fiber regeneration.

Bcl-2 and Bax protein expression in human myopathies

Expression of the apoptosis-related proteins Bcl-2 and Bax was analysed by means of immunohistochemistry in muscle biopsies from 13 patients suffering from different muscular diseases (inclusion body myositis n=4, polymyositis n=3, Becker muscular dystrophy n=4, necrotizing myopathy n=2, and controls n=4), in an attempt to learn about the role of these proteins in human muscle diseases associated with muscle fiber necrosis and regeneration. Increased Bcl-2 and Bax immunoreactivity was observed as fine granular precipitates in the cytoplasm or as subsarcolemmal aggregates in pathological cases. Increased Bcl-2 and Bax immunoreactivity was detected in some necrotic fibers, regenerating fibers, ring fibers and some apparently normal muscle fibers. In addition, increased Bcl-2 and Bax immunoreactivity was observed in the periphery of rimmed vacuoles and in muscle fibers with abnormal mitochondria in patients suffering from inclusion body myositis. Double-labelling immunohistochemistry disclosed co-localization of both proteins in about 50% of Bcl-2-immunoreactive fibers. Finally, double-labelling immunohistochemistry using N-CAM antibodies revealed that some Bax-positive fibers were regenerating fibers. Since increased Bax immunoreactivity was not restricted to necrotic muscle fibers, the present results suggest that over-expression of this protein in human myopathies is probably independent of the process of cell death.

[Neuropathy by n-hexanes: a generalized disorder of the intermediate filaments]

BACKGROUND

Chronic inhalation of glues containing n-hexanes produces neurofilament (NF) accumulation which induces sensory-motor polyneuropathy. In vitro assays have shown this toxic substance causes intermediate filaments (IF) aggregation in non-neuronal cells.

OBJECTIVE

To describe intermediate filament changes in human pathology due to n-hexanes.

PATIENTS AND METHODS

Sural nerve and skin biopsy samples from 2 patients who suffered from a severe sensory-motor polyneuropathy after prolonged inhalation of glue containing n-hexane were examined with electron microscopy and vimentin and phosphorylated NF immunocytochemistry.

RESULTS

Abnormal accumulations of NF and NF-immunoreactive products occurred in nerve fibers and increased numbers of fibrils were observed in endoneurial endothelial cells of the sural nerve. In addition, abnormal vimentin-immunoreactive deposition was seen in fibroblasts and capillaries of the skin. The present results suggest that high doses of n-hexane cause a diffuse IF disorder in a similar form as occurs in giant axonal neuropathy.

CONCLUSION

IF aggregation can occur in non-neuronal cells in humans, as has been previously proved in in vitro experiments. The presence of IF accumulations in Schwann cells, as seen in the ultrastructural examination, together with the electrophysiological findings showing an early decrease of sensory and motor nerve conduction velocities, suggests the existence of a primary myelinic disorder associated with axonal damage.

Expression of myogenic regulatory factors (MRFs) in human neuromuscular disorders

Immunohistochemical studies using antibodies to myogenic regulatory factors (MRFs) Myo D, myogenin, myf-5, and myf-6, and transcription factors c-Fos and c-Jun, were performed on muscle biopsies from patients suffering from Duchenne and Becker muscular dystrophies, polymyositis, and denervation atrophy, to investigate whether expression of these factors occurs during degeneration and regeneration of adult muscle fibres. Strong Myo D, myogenin, myf-5 and myf-6 immunoreactivity was observed in the nuclei of small regenerating fibres and satellite cells, as revealed by double-labelling immunohistochemistry with N-CAM antibodies, in Duchenne and Becker muscular dystrophies and in polymyositis. This suggests that the myogenic programme is activated during regeneration of adult human muscle fibres. In addition, strong myf-6 and c-Jun immunoreactivity was found in the cytoplasm of some necrotic muscle fibres in patients with Duchenne and Becker muscular dystrophies and in patients with polymyositis. The latter findings suggest that strong cytoplasmic expression of myf-6 and c-Jun is related to the process of muscle fibre degeneration that occurs in these conditions. Increased Myo D, myogenin, myf-5 and myf-6 immunoreactivity was not observed in the nuclei of denervated muscle fibres, although strong c-Fos and c-Jun immunoreactivity was seen in the nuclei of denervated muscle fibres; this suggests that denervation triggers the expression of these transcription factors. Taken together, these observations demonstrate that MRFs and c-Fos and c-Jun are selectively expressed in different human muscular disorders.