Chronic generalized spinal muscular atrophy of infancy and childhood. Arrested Werdnig-Hoffman disease

Phosphatase and tensin homologue: a therapeutic target for SMA

Spinal muscular atrophy (SMA) is one of the most common juvenile neurodegenerative diseases, which can be associated with child mortality. SMA is caused by a mutation of ubiquitously expressed gene, Survival Motor Neuron1 (SMN1), leading to reduced SMN protein and the motor neuron death. The disease is incurable and the only therapeutic strategy to follow is to improve the expression of SMN protein levels in motor neurons. Significant numbers of motor neurons in SMA mice and SMA cultures are caspase positive with condensed nuclei, suggesting that these cells are prone to a process of cell death called apoptosis. Searching for other potential molecules or signaling pathways that are neuroprotective for central nervous system (CNS) insults is essential for widening the scope of developmental medicine. PTEN, a Phosphatase and Tensin homologue, is a tumor suppressor, which is widely expressed in CNS. PTEN depletion activates anti-apoptotic factors and it is evident that the pathway plays an important protective role in many neurodegenerative disorders. It functions as a negative regulator of PIP3/AKT pathway and thereby modulates its downstream cellular functions through lipid phosphatase activity. Moreover, previous reports from our group demonstrated that, PTEN depletion using viral vector delivery system in SMN delta7 mice reduces disease pathology, with significant rescue on survival rate and the body weight of the SMA mice. Thus knockdown/depletion/mutation of PTEN and manipulation of PTEN medicated Akt/PKB signaling pathway may represent an important therapeutic strategy to promote motor neuron survival in SMA.

Intramedullary astrocytoma presenting as spinal muscular atrophy

We present a 6-year-old patient with a spinal cord tumor who had been followed with the diagnosis of spinal muscular atrophy since the age of 23 months. Reasons for reevaluating the diagnosis of spinal muscular atrophy were the early onset of scoliosis, the slight asymmetry in weakness of extremities, and the appearance of urinary retention in the last 3 days. Magnetic resonance imaging revealed a very long, intramedullary tumor extending from the level of the seventh cervical segment to the conus medullaris, later reported to be a grade I astrocytoma. We therefore recommend that magnetic resonance imaging, a noninvasive and sensitive technique for intraspinal pathologies, be performed in every patient with an atypical form of spinal muscular atrophy.

Brain atrophy in Werdnig-Hoffmann disease

CT scan imaging of the brain was done in eight children with Werdnig-Hoffmann Disease. Seven of them showed generalized cerebral cortical atrophy and one had low attenuated, non-enhancing areas in the white matter involving both frontal lobes. These changes could be due to repeated episodes of hypoxic injury.

A predominantly cervical form of spinal muscular atrophy

Clinical heterogeneity within the group of spinal muscular atrophies (SMA) in children can pose practical problems of diagnosis, prognosis and genetic counselling. In addition to the classic forms, unusual cases have been described. Five children with an atypical type of SMA are reported, characterised by early involvement of cervical muscles contrasting with initially mild or absent affection of peripheral muscles. Secondary involvement of respiratory muscles was responsible for the death of three children in the second to fourth year. The disorder may be recessively inherited.

Genetic mapping of chronic childhood-onset spinal muscular atrophy to chromosome 5q11.2-13.3

SPINAL muscular atrophy (SMA) describes a group of heritable degenerative diseases that selectively affect the alpha-motor neuron. Childhood-onset SMAs rank second in frequency to cystic fibrosis among autosomal recessive disorders, and are the leading cause of heritable infant mortality. Predictions that genetic heterogeneity underlies the differences between types of SMA, together with the aggressive nature of the most-severe infantile form, make linkage analysis of SMA potentially complex. We have now analysed 13 clinically heterogeneous SMA families. We find that 'chronic' childhood-onset SMA (including intermediate SMA or SMA type II, and Kugelberg-Welander or SMA type III) is genetically homogeneous, mapping to chromosomal region 5q11.2-13.3.

Unusual pedigree patterns in seven families with spinal muscular atrophy; further evidence for the allelic model hypothesis

Clinical and genetic findings are presented in 18 patients, from 7 pedigrees with different types of spinal muscular atrophy (SMA). The SMA diagnosis was based on EMG and muscle biopsy findings. All 7 pedigrees show an unusual genetic pattern, not consistent with simple autosomal recessive inheritance. Furthermore, in 6 of the 7 pedigrees different types of SMA were present within each pedigree. Our findings can be explained by an extension of a multiple alleles hypothesis originally described by Becker in 1964.

The discovery of neuronopathy and neuropathy as a cause of progressive paralysis in childhood. The historical origins of modern differential diagnosis in neuromuscular disease

The concept of the differential diagnosis has a central place in all clinical medicine. In neurology and paediatrics, evolution of thought concerning the differential diagnosis of the child presenting with symptoms of neuromuscular disease was far in advance of similar diagnostic approaches to problems of infectious, infective and neoplastic disease; and as such forms a significant historical model for the development of modern clinical approaches to the sick or disabled child. The account presented in this paper provides a detailed historical review of the development of thought relating to the causes of neuromuscular disease. Nosological developments concerning diseases of the motor unit can be conveniently classified into three periods: (a) a "state of the art" period to 1850; (b) 1850-1890 - a period of parallel and interdependent advances in both normal neuro-anatomy and neurophysiology, and diseases recognized as variations from such norms. In this era Duchenne was the first to write about the differential diagnosis of the progressive muscular paralysis in childhood; and Gowers was the first to write specifically on the hereditary transmission of this group of diseases; (c) in 1891 was described the first case of childhood neuronopathy recognized as such, and with this development was ushered in the modern era of clinical differential diagnosis of childhood neuromuscular disease. The "splitters" have won the great debate concerning the clinical approach to neurological diseases. The continual further refining of an exact diagnosis is the only way in which a realistic prognosis can be forecast, correct genetic counseling can be offered, and (if the condition is treatable) optimal therapy can be introduced.

Distal spinal muscular atrophy. A clinical and genetic study of 8 kindreds

Twelve patients (8 kindreds) with distal SMA are described, and an analysis presented of their clinical and genetic features. Distal SMA accounted for 10% of all patients with SMA in a total population survey of this disease in North-East England. The parental consanguinity rate is high, occurring in 3 of the 8 kindreds reported; the sex ratio was 1.0; the segregation ratio of sibs did not differ from 0.25. Intrafamilial concordance for clinical features of the disease is high. This current data is consistent with a suggested aetiology of two separate autosomal recessive genes. Clinical features are discussed and a review of the literature presented. The disease is only slowly progressive, but one of the genetic types may present with infantile or early juvenile onset; there is no evidence that it shortens life. 50% of cases did not have a normal gait after 4 years of age; 50% could not run after 17 years of age; and 50% could not walk unaided after 28 years of age. Details of prognosis, and principles of genetic counselling in this disease are discussed.

Blood selenium in chronic spinal muscular atrophy

The spinal muscular atrophies (SMA) of childhood comprise the second most common fatal recessive disease after cystic fibrosis, yet the nature of the biochemical defect causing the anterior horn cell degeneration is totally unknown. Recent reports of a cluster of adult motor neurone disease cases from a high seleniferous area in South Dakota have prompted the study of blood selenium in children with SMA in Australia. Eight children with chronic SMA were tested, in addition to 9 obligate heterozygote carriers of the gene. Blood selenium levels of patients and carriers did not differ significantly from that observed in controls. The mammalian effects of selenium toxicity are discussed.

Incidence, prevalence, and gene frequency studies of chronic childhood spinal muscular atrophy

A total population study of chronic childhood spinal muscular atrophy (arrested Werdnig-Hoffmann disease, Kugelberg-Welander disease, SMA type II and III) was undertaken in north-east England to establish gene and carrier frequencies, incidence, and prevalence. The incidence of this disease was 1 in 24 100 live births. Prevalence was 1.20 per 100,000 of the general population. A technique for estimating an autosomal recessive gene frequency in the known presence of dominant new mutations (or phenocopies), using data from a segregation analysis, is described. Gene frequency was in the range (0.00451 to 0.00659 (95% confidence limits), with a working estimate of 0.0055. Carrier rates for the autosomal recessive gene concerned were 1 in 76 to 1 in 111 (95%) confidence limits), with a working estimate of 1 in 90 for genetic counselling purposes.

Autosomal dominant spinal muscular atrophy: a clinical and genetic study

A clinical and genetic study of 6 kindreds (13 patients) with autosomal dominant spinal muscular atrophy is presented. Evidence is presented to indicate that two separate autosomal dominant genes are involved. One of these causes clinical disease with onset in early childhood (birth--8 years), which is relatively benign and in which proximal selectively of muscle involvement is not marked. A separate autosomal dominant gene causes a disease with onset in adult life (median age 37 years), showing marked initial proximal selectively; this disease may be more rapid in its clinical progression. Penetrance of both genes approaches 100%. Incidence figures are presented; less than 2% of all cases of childhood onset spinal muscular atrophy, but 30% of adult onset cases, are due to an autosomal dominant gene transmitted from an affected parent. Implications for prognosis, diagnosis and genetic counselling are discussed. A review of 11 kindreds of dominant spinal muscular atrophy in the literature is presented.

A clinical study of chronic childhood spinal muscular atrophy. A review of 141 cases

The case histories and clinical details of 141 children (67 males and 74 females) with chronic childhood spinal muscular atrophy (SMA) have been reviewed. Hundred of these children were alive at the time of the study. The cases comprise a consecutive unselected series of all with this disease who presented to two large English neurological centres over a 10-year tracing period. Chronic childhood SMA is defined here as a progressive disease of anterior horn cells with initial proximal selectivity, which does not of itself cause death before 18 months of age. Clinical signs are first manifest between birth and 8 years of age, but in 95% before 3 years. Cumulative frequency tables for motor skills are presented; 46% of children never walked, even with orthopaedic aids; 37.6% were able to walk unaided at some stage. No child was able to run after 12 years of age. Late-presenting sporadic cases retain motor skills longer than do familial cases. A sex influence on the clinical course of the disease has been demonstrated, males being more severely affected. Cumulative frequency curves for age-at-onset and age-at-presentation have been compiled. A sib of an affected index case, still clinically normal at 2 years of age, has passed 90 percent of his risk period; the use of such cumulative frequency curves for studies of carrier-frequency and incidence is discussed. The median age at death for this disease exceeds 10 years. The range encompassed by the clinical spectrum is discussed.

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.

Anterior-horn cell degeneration and gross calf hypertrophy with adolescent onset. A new spinal muscular atrophy syndrome

A new variant of spinal muscular atrophy (S.M.A.), characterised by adolescent onset, gross hypertrophy of calves, and a slowly progressive clinical course, was found in 5 patients, 3 of them in a series of 102 cases being studied in North-East England. Biopsy and electrophysiological studies indicated the presence of chronic progressive degeneration of anterior-horn cells.

[Werdnig-Hoffmann disease: report of two cases?]

Two cases of familial spinal muscular atrophy with onset in infancy are reported. The author makes an attempt to categorize them and concludes by Werdnig-Hoffmann disease.

Ultrastructural aspects of muscle and nerve in Werdnig-Hoffmann disease

The authors describe in biopsies from 6 cases of Werdnig-Hoffmann disease, including 2 of the more benign type, the ultrastructural typical aspects of denervation. They compare their findings with those of other workers. The striking points are the great variation in the diameter of the muscle fibres and the myofibrils, the disorganisation of the myofibrils, the sarcomeres and the filaments, with persistance of the relations between thick and thin filaments at various levels, the modifications of the Z-band and the triads in chains. The folds and the basement membrane are examined. Centrioles are present in a muscle fibre and in a satellite. Glycogen is very abundant. The nerves seem normal but some Schwann cells contain pi granules which are not observed usually at the age of the patient. The end plates and a muscle spindle are normal.