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Functional recovery. A major risk factor for the development of postpoliomyelitis muscular atrophy.

A retrospective study was undertaken to identify potential risk factors for the development of progressive postpoliomyelitis muscular atrophy (PPMA). Patients with PPMA (n = 57) were compared with patients with a history of poliomyelitis but without a history of progressive weakness (n = 49). Patients who later developed PPMA had histories of more widespread acute paralysis, but relatively greater functional recovery. They were less disabled, and reported higher recent activity levels. Seventy-nine percent of the total variance between the PPMA and control groups could be accounted for by recovery alone (ie, severity minus disability). Functional recovery is generally attributed to reinnervation of sarcomeres by collateral sprouting from surviving lower motor neurons. Since degree of recovery predicts the risk of developing PPMA, our findings suggest that enlarged motor units may carry an increased susceptibility for dysfunction and/or degeneration.

Adult↗

Disaggregation of polyribosomes in the spinal anterior horn cells in a patient with X-linked spinal and bulbar muscular atrophy.

The spinal anterior horn cells (AHCs) in a patient with X-linked spinal and bulbar muscular atrophy (SBMA) were examined by light and electron microscopy, giving special attention to alterations in the rough endoplasmic reticulum (ER). Seven age-matched subjects were used as controls. The patient with SBMA showed a severe decrease of AHCs, but the Nissl substance in the remaining AHCs appeared well preserved on light microscopy. Electron microscopy revealed a relatively well preserved parallel lamellar pattern of ER and marked disaggregation of the polyribosomes surrounding the ER in the remaining AHCs. These findings indicate that the Nissl substance was affected in spite of its light microscopic appearance in SBMA, and that the AHCs degenerate through disaggregation of the polyribosomes of the ER.

Anterior Horn Cells↗

[Correlation of electrophysiologic findings in neural muscular atrophy].

In a collective of 22 patients (18 adults, 4 children) with the clinical diagnosis of peroneal muscular atrophy the correlation of various neurophysiological parameters was examined. These included electromyography, motor and sensory nerve conduction velocity, visual (VEP), acoustic (AEP) and somatosensory (SEP) evoked potentials and conventional EEG. In all cases we found a high correlation between the findings of nerve conduction velocities and somatosensory evoked responses. Acoustic evoked potentials were examined in 18 cases and showed 10 pathological findings; visual evoked responses were also examined in 18 cases and produced 5 pathological findings. If nerve conduction velocity measurements are possible, SEP examinations are superfluous as they do not provide additional information. On the other hand, VEP and AEP testing is warrented in all cases to document the impairment of central nervous pathways.

Adult↗

[Spinal pathology in spinal muscular atrophy in comparison with amyotrophic lateral sclerosis].

We analyze neuronal cytopathology and secondary reactions in spinal-muscular atrophy (SMA) in comparison with amyotrophic lateral sclerosis (ALS). In a series of SMA and ALS cases, immunohistochemistry was performed on spinal cord sections for neuronal, astroglial and microglial antigens, ubiquitin and tau proteins. Swollen motoneurons staining for phosphorylated neurofilament proteins are seen in most SMA but few ALS cases. Ubiquitinated inclusions are found only in ALS. In SMA, glial bundles are prominent in anterior roots, to lesser extent in posterior roots. In ALS, glial bundles are seen only in some cases. While basic histopathologies are similar in both types of motor neurone diseases, neuronal cytoskeletal pathology is more prominent in SMA, possibly reflecting a more acute degenerative process. The presence of axon spheroids and glial bundles also in posterior horns/roots of both types of motor neurone disease suggests spread of degenerative pathology beyond the motor system.

Amyotrophic Lateral Sclerosis↗

Focal cervical poliopathy causing juvenile muscular atrophy of distal upper extremity: a pathological study.

A new clinical entity under the name of "juvenile muscular atrophy of unilateral upper extremity" was first described in 1959. Although about 150 cases in Japan, and several additional cases in other countries, have been clinically reported in the literature, the pathology has remained unknown because of the benign course of the disease. The first necropsy findings are reported, obtained from a patient with this disease, who died of lung cancer at the age of 38, 23 years after the onset of the disease. The lesions existed only in the anterior horns of the spinal cord at C5 approximately T1, particularly marked at C7 and C8, showing shrinkage and necrosis, degeneration of various degrees of large and small nerve cells, and mild gliosis. The pathological findings differ from those of reported cases of spinal vascular disorders, but some circulatory insufficiency in the territory of the spinal cord would seem to be suggested, although the underlying aetiology remains unknown.

Adult↗

A gene for a severe lethal form of X-linked arthrogryposis (X-linked infantile spinal muscular atrophy) maps to human chromosome Xp11.3-q11.2.

X-linked arthrogryposis Type I (X-linked infantile spinal muscular atrophy) is a rare disorder showing hypotonia, areflexia, and multiple congenital contractures (arthrogryposis) associated with loss of anterior horn cells and death in infancy. We have studied an X-linked arthrogryposis family using highly polymorphic microsatellite markers throughout the X chromosome. Meiotic breakpoint analysis (concordance analysis) based on shared regions of the founder X chromosome was successful in localizing the X-linked arthrogryposis gene to Xp11.3-q11.2. In this region, the highest two-point lod score was found with DXS991 (Zmax = 2.63, theta = 0.00). In multipoint linkage analysis covering the entire X chromosome, only the region defined by MAOB and DXS991 showed positive lod scores and all other regions showed negative lod scores. These data establish the first gene mapping assignment of an X-linked lethal form of human lower motor neuron disease.

Adolescent↗

Prenatal diagnosis of spinal muscular atrophy by direct molecular analysis: efficacy and potential pitfalls.

The efficacy of direct prenatal diagnosis for spinal muscular atrophy (SMA) is demonstrated, and the potential pitfalls with this type of analysis are highlighted in the largest prospective single-center prenatal series in the United States. The presence or absence of exons 7 and 8 of the SMN gene was determined from 66 fetuses from 51 families. Direct and cultured chorionic villus samples (CVS) and amniocytes were analyzed. DNA analysis to exclude maternal cell contamination was performed on all CVS. Follow-up was obtained for 48 cases; 13 pregnancies continue. One child predicted to be affected with SMA remains asymptomatic at 13 months. Thirty-three cases were confirmed to be clinically unaffected in agreement with the prenatal molecular results. Three of 24 CVS had maternal cell contamination. In conclusion, direct molecular analysis of either CVS or amniocytes is highly accurate in the prenatal diagnosis of SMA. However, maternal cell contamination of CVS samples can confound these analyses, and the possibility of contamination must be excluded routinely.

Amniocentesis↗

Use of genetic and physical mapping to locate the spinal muscular atrophy locus between two new highly polymorphic DNA markers.

The gene for autosomal recessive forms of spinal muscular atrophy (SMA) has recently been mapped to chromosome 5q13, within a 4-cM region between the blocks D5S465/D5S125 and MAP-1B/D5S112. We identified two new highly polymorphic microsatellite DNA markers--namely, AFM265wf5 (D5S629) and AFM281yh9 (D5S637)--which are the closest markers to the SMA locus. Multilocus analysis by the location-score method was used to establish the best estimate of the SMA gene location. Our data suggest that the most likely location for SMA is between locus D5S629 and the block D5S637/D5S351/MAP-1B/D5S112/D5S357. Genetic analysis of inbred SMA families, based on homozygosity by descent and physical mapping using mega-YACs, gave additional information for the loci order as follows: cen-D5S6-D5S125/D5S465-D5S435-D5S629-SMA-+ ++D5S637-D5S351-MAP-1B/D5S112-D5S357- D5S39-tel. These data give the direction for bidirectional walking in order to clone this interval and isolate the SMA gene.

Child↗

Juvenile muscular atrophy of distal upper extremity associated with airway allergy: two cases successfully treated by plasma exchange.

Juvenile muscular atrophy of the distal upper extremity (JMADUE) is postulated to be a type of flexion myelopathy. However, patients with typical clinical features of JMADUE but without evidence of flexion myelopathy have been reported. We recently reported a significant association of JMADUE with airway allergy. Here we report the successful treatment by plasma exchange (PE) of two patients with both airway allergy and JMADUE without evidence of flexion myelopathy. Patient 1 had a 5-year history of allergic rhinitis and high titers of mite antigen-specific IgE, and patient 2 had an 8-year history of pollinosis and high titers of cedar pollen-specific IgE. Both patients noted progressive distal muscle atrophy and weakness of the upper extremities: patient 1 for 3 months and patient 2 for 3 years. Neurologically, both showed asymmetric intrinsic hand muscle atrophy, oblique atrophy of the forearm muscles, and weakness and contraction fasciculation (minipolymyoclonus) of these muscles without any sensory impairment. Neither had any evidence of flexion myelopathy on magnetic resonance imaging (MRI) in a flexed position. Both were subjected to PE three times. Soon after the PEs, both showed improvement of distal muscle weakness of the upper extremities and marked reduction of contraction fasciculation of the forearm muscles. Patient 1 showed marked reduction in ongoing denervation potentials in the distal muscles on needle electromyography, while patient 2 showed marked improvement of F wave persistence of bilateral median and ulnar nerves. Serum total and allergen-specific IgE decreased after PEs in both patients. PE was thus considered to be effective in these two patients having JMADUE without evidence of flexion myelopathy. These observations may suggest the involvement of an immune-mediated process in the neural damage of JMADUE without evidence of flexion myelopathy, especially in patients with atopic diathesis, and may support the notion that JMADUE is etiologically heterogeneous.

Adolescent↗

Best practice guidelines for molecular analysis in spinal muscular atrophy.

With a prevalence of approximately 1/10 000, and a carrier frequency of 1/40-1/60 the proximal spinal muscular atrophies (SMAs) are among the most frequent autosomal recessive hereditary disorders. Patients can be classified clinically into four groups: acute, intermediate, mild, and adult (SMA types I, II, III, and IV, respectively). The complexity and instability of the genomic region at chromosome 5q13 harbouring the disease-causing survival motor neuron 1 (SMN1) gene hamper molecular diagnosis in SMA. In addition, affected individuals with SMA-like phenotypes not caused by SMN1, and asymptomatic individuals with two mutant alleles exist. The SMN gene is present in at least one telomeric (SMN1) and one centromeric copy (SMN2) per chromosome in normal (non-carrier) individuals, although chromosomes containing more copies of SMN1 and/or SMN2 exist. Moreover, the two SMN genes (SMN1 and SMN2) are highly homologous and contain only five base-pair differences within their 3' ends. Also, a relatively high de novo frequency is present in SMA. Guidelines for molecular analysis in diagnostic applications, carrier detection, and prenatal analysis using direct and indirect approaches are described. Overviews of materials used in the molecular diagnosis as well as Internet resources are included.

Cyclic AMP Response Element-Binding Protein↗

Prenatal prediction of spinal muscular atrophy by SMN deletion analysis.

The objective of this study was to provide prenatal prediction of spinal muscular atrophy (SMA) by survival motor neuron (SMN) gene deletion analysis and genetic counseling in families with previous child affected with SMA. The SMN gene is absent or interrupted in approximately 95% of SMA patients independence of clinical severity. We study four families with one previous child affected in each by performing the SMN deletion analysis in the index case. When a homozygous deletion in exon 7 or exon 8 is found, we offer prenatal prediction to the family. All four index cases had homozygous deletions of the SMN gene. Prenatal diagnosis by amniocentesis was performed in all pregnancies. Two pregnancies were positive for the homozygous deletion of the SMN gene, non-directive counseling was given and the two pregnancies were terminated. The other two pregnancies showed no deletion of the SMN gene. The unborn child is yet to be followed up. The prenatal prediction of SMA shows considerable requirements and potential effectiveness in prevention of the SMA in families at risk which cut the cost of care in this incurable disease.

Amniocentesis↗

Prenatal diagnosis of the acute form of proximal spinal muscular atrophy: experience on the acceptance of linkage analyses by the families.

The acute form of proximal spinal muscular atrophy (SMA) is a severe autosomal recessive inherited neuromuscular disorder. It has been mapped to chromosome 5q 11.2-13.3. Using restriction fragment length polymorphisms (RFLPs) or (CA)n repeats of DNA probes in this region, prenatal diagnosis is, in principle, possible. Misdiagnosis can be due to incorrect diagnosis in the index patient, and crossing-over events. Using the DNA probes D5S6, D5S112, D5S39, and D5S78, we cover a region of 10.4 mega-base pairs (Mbp) of partially NotI-digested genomic DNA without overlap of fragments. The DNA probes D5S6 and D5S112, most likely flanking the SMA gene, cover a distance of about 6.6 Mbp. This corresponds to the genetic distance of 6 cM (Morrison et al., 1992; Daniels et al., 1992). But since the precise localization of the SMA gene is still unknown (Simard et al., 1992), a 10 per cent risk of misdiagnoses due to crossing-over events cannot be excluded. The acceptance of this 10 per cent risk for prenatal diagnoses differs in SMA families. We observed a case in which a woman accepted a 25 per cent risk because RFLPs and (CA)n repeats were both uninformative. In contrast, another family did not accept the minimal 10 per cent risk and the pregnancy was terminated. In two families, we performed prenatal diagnosis by linkage analysis. One child predicted to be healthy has been born in the meantime and has shown no indication of SMA during her first 8 months.

Acute Disease↗

A genetic study of subacute and chronic spinal muscular atrophy in childhood. A nosological analysis of 124 index patients.

A genetic study of the subacute spinal muscular atrophies (SMA) of late infancy and early childhood has been undertaken. All such patients with chronic disease (with ages at onset up to 14 years, and excluding SMA Type I) known to 2 large Neurological Centres were reassessed clinically and genetically. There were 124 index patients (67 females and 57 males) and 17 secondary cases, which formed two consecutive unselected series. To investigate the genetic composition of this group, 4 nosological approaches were used; cluster analysis of clinical features of the disease, Haldane's sib-sib analysis on familial cases, interpretation of frequency distribution histograms, and a segregation analysis. A single autosomal recessive gene accounts for over 90% of cases, causes a clinical syndrome which manifests its first clinical signs before 5 years of age and in almost all cases before two years of age, but which is compatible with life into the third decade. Moderate intrafamilial discordance for some clinical features may be observed, but no genetic heterogeneity within this group was demonstrated. A small group of cases is caused by (a) new dominant mutation(s), or (b) is composed of phenocopies, or both. This relatively uncommon form may comprise the majority of late-presenting cases, and may account for all cases which manifest the first signs after 5 years of age. The spectrum of age-at-onset of this group cannot be determined at present, but the disease may be manifest before the age of two years; it is clinically indistinguishable from SMA caused by an autosomal recessive gene. The literature has been reviewed in the light of these findings. Empirical risks for use in genetic counselling are presented.

Child, Preschool↗

Distal chronic spinal muscular atrophy involving the hands.

Six patients are described with a history of slowly progressive wasting of the muscle of the hands and forearms extending over periods of up to 20 years. The clinical, radiological, and electrophysiological findings were consistent with a diagnosis of chronic anterior horn cell degeneration. It is suggested that the patients are affected by a form of distal chronic spinal muscular atrophy affecting the hands.

Action Potentials↗

Physical capacity in non-ambulatory people with Duchenne muscular dystrophy or spinal muscular atrophy: a longitudinal study.

The purpose of this study was to describe functional ability, muscle strength, forced vital capacity, and clinical events in participants with Duchenne muscular dystrophy (DMD) or spinal muscular atrophy (SMA) in the non-ambulatory stages of the diseases. Nineteen non-ambulatory participants with DMD (all males; 13 to 24 years) and 13 with SMA (six males, seven females; 11 to 57 years) were assessed once a year over 5 years. The assessments comprised functional ability measured with the EK scale and upper extremity grade, muscle strength measured with the manual muscle test, and forced vital capacity defined as a percentage of normal values (FVC%). In the DMD group all variables measured deteriorated and there was a direct correlation between them. In the SMA group only muscle strength and FVC% deteriorated and there was no close relation between the variables measured. In the DMD group, 16 participants had cardiorespiratory clinical events leading to death in five cases. In the SMA group only four participants had respiratory clinical events, none leading to death. Although the participants with SMA had been extremely weak and non-ambulatory since early childhood they were older and less exposed to life-threatening events than the participants with DMD.

Activities of Daily Living↗