Abnormalities of skeletal muscle maturation in brain damaged children: a histochemical study

Dysmaturation neuromyopathy: correlation with minimal neuropathy in sural nerve biopsies

Dysmaturation (neuro)myopathy without specific histochemical or cytoarchitectural characteristics accounts for many cases of hypotonia in infancy. We obtained a maturation profile for type I and type II fibers from birth to 6 years of age, from which a classification of fiber dysmaturation based on fiber-type hypotrophy and coefficient of fiber variation is presented. We analyzed the morphometric, ultrastructural, and single fiber teasing findings in the sural nerve of ten infants with hypotonia and dysmaturation myopathy based on the above classification. Data on endoneurial area, myelinated fiber density, proportion of large (greater than 6 micron) myelinated fibers, unmyelinated fiber density, regression analyses of myelin area:axon area, and mean myelin thickness were developed. Abnormalities in large myelinated fiber density (3 cases), disturbances in myelination index (5), and single fiber teasing abnormalities in internode length (1) were found. Ultrastructural abnormalities were observed and classified as group 0 changes similar to the five control nerves; group 1, in which rare fibers showed degeneration or basement membrane duplication; and group 2, which was characterized by multiple abnormalities including degenerate nuclei, amyelinate fibers, degeneration/regeneration, excessive basal lamina reduplication, and hypomyelination. This study provides evidence that minimal neuropathic abnormalities are present in the sural nerve of infants carrying a diagnosis of dysmaturation neuromyopathy.

Arthrogryposis multiplex congenita: otolaryngologic diagnosis and management

Arthrogryposis multiplex congenita (AMC) is an uncommon congenital disorder characterized by multiple fixed joint deformities and non-progressive neuromuscular dysfunction. A small fraction of these infants will present with otolaryngologic problems resulting from cranial nerve weakness, muscle dysplasia, or structural dysharmony of the head and neck. The charts of 50 patients with AMC were reviewed to determine the incidence of these findings. A summary of the literature is presented discussing the etiology, pathophysiology, diagnosis and management of this interesting clinical problem.

Infantile myopathy with type 1 fibre specific hypertrophy

Two children are described whose clinical and muscle biopsy findings suggested a previously unrecognised variant of congenital fibre-type disproportion myopathy, characterised by selective hypertrophy of type 1 fibres.

Muscular alteration in agyria with pyramidal tract anomaly

A 4-year-old boy with a history of muscular hypotonia, mental retardation, microcephaly, and generalized convulsions was found at autopsy to have agyria, agenesis of the anterior commissure and posterior corpus callosum as well as an abnormal decussation of pyramidal tracts which descended in the spinal dorsal columns. Postmortem muscular alterations included type IIc fiber hypertrophy and type I fiber grouping, variably expressed in individual muscles and intramuscular fascicles. This may represent a developmental delay compatible with a gestational age between the 34th and 40th week. These studies also indicate the importance of examining multiple samples of postmortem muscles and muscles from patients afflicted with cerebral malformations.

Cerebral dysgeneses and their influence on fetal muscle development

Abnormal suprasegmental influences of the brainstem and cerebellum on the developing motor unit during the histochemical stage of muscle development (20-28 weeks gestation) may alter the rate of maturation of striated muscle or may cause abnormal proportions and relative sizes of histochemical fibre types. Such aberrations without primary myopathic or denervative changes are commonly found in children with cerebral malformations, particularly associated with cerebellar hypoplasia. Upper motor neuron disease during embryonic life may explain histochemical alterations in some nonprogressive 'congenital myopathies' such as congenital muscle fibre-type disproportion, nemaline rod disease, and central core disease. Suprasegmental factors also may contribute to some aspects of the muscle pathology in the muscular dystrophies, especially the Fukuyama type of congenital muscular dystrophy regularly associated with cerebral dysgenesis. Fibre-type predominance or delayed histochemical differentiation thus may serve as a useful marker, in the muscle biopsy, of upper motor neuron disease. During the critical period of muscle development implicated, the corticospinal tract probably is of much less importance in muscle maturation than the multiple small bulbospinal pathways which also subserve motor control in nonmammalian vertebrates.

Le Cerveau Influence-t-il le Développement Musculaire du Foetus Humain?

Does the human fetal brain influence muscle development? The importance of suprasegmental cerebral influence on developing human fetal muscle is less well understood than the control of histochemical differentiation of muscle by the motor neuron. Muscle biopsies of 21 hypotonic infants and children with nonprogressive congenital lesions of the cerebellum and/or brainstem were studied by histochemical methods. Two neonates who died with severely dysplastic brains and no descending motor tracts had normal muscle. The others, particularly those with cerebellar hypoplasia, had delayed muscle maturation, selective predominance of type I or II muscle fibres or disproportion in fibre sizes. It is concluded that the motor unit is capable of developing normally without suprasegmental influence, but that an abnormal balance of descending impulses may alter histochemical differentiation of fetal muscle. The small ‘subcorticospinal’ pathways arising in the brainstem probably are more influential than the larger corticospinal tract because of later myelination in the latter. The muscle biopsy thus serves to provide evidence of suprasegmental disease in infantile hypotonia.

Arthrogryposis multiplex congenita in an infant with posterior agenesis of the corpus callosum

A term male infant with arthrogryposis multiplex congenita and agenesis of the corpus callosum is described. Physical examination revealed multiplex dysmorphic features and fixed joints. A muscle biopsy showed type II fibers to be more than 12% smaller than type I fibers, consistent with the diagnosis of fiber type disproportion. The CT scan disclosed absence of the posterior corpus callosum and moderate atrophy of the cerebellar hemispheres. The pathogenetic mechanism for the muscle (and thus joint) abnormalities of this infant is discussed with respect to a central etiology.

The myopathology of Behçet's disease--a histochemical, light-, and electron-microscopic study

The myopathology of Behçet's disease is described in 7 patients using conventional light microscopy, histochemistry, high-resolution light microscopy and electron microscopy. Two patients had clinical evidence of peripheral neuropathy: 5 patients had no clinical evidence of neuromuscular involvement. Histochemical profile of muscle in all patients was normal. Abnormalities in muscle histology using conventional light microscopy were found in only 1 patient. High-resolution light microscopy revealed abnormalities in 3 patients whereas electron microscopy revealed abnormalities in muscle of all 7 patients. The myopathology of Behçet's disease includes thickening of capillary basement membrane, excessive pleating of sarcolemma, subsarcolemmal aggregates of mitochondria and glycogen, disorganization and breakdown of myofibrils, central nucleation and the presence of a variety of cytoplasmic inclusions. No virus particles were present.

Central nuclear counts in muscle fibres before and during treatment in hypothyroid myopathy

Serial percutaneous needle muscle biopsies of vastus lateralis were studied in 10 patients who had varying degrees of hypothyroid myopathy. The biopsies were taken before and during treatment with l-thyroxine. Before treatment the most severely clinically affected patients showed type II muscle fibre atrophy and loss, together with increased central nuclear counts preferentially affecting the type II muscle fibre. Both the type II muscle fibre atrophy and loss and the increased central nuclear counts tended to return towards normal values during treatment with l-thyroxine. The severity of myopathic symptoms before and during treatment correlated with the biochemical evidence of hypothyroidism, a type II fibre atrophy, and increased central nuclear counts. The severity of myopathic signs before and during treatment was correlated with both a type II fibre atrophy and loss and increased central nuclear counts. There was no evidence that the myopathic signs before and during treatment were related to the biochemical parameters of hypothyroidism, except the level of thyroid stimulating hormone. It is suggested that sequential studies of muscle fibre percentages, diameters, and central nuclear counts may provide an additional method of assessing the response to treatment in hypothyroid and possibly other types of myopathy. When increased central nuclear counts are confined to a specific muscle fibre type, this may suggest a hitherto unsuspected specificity of muscle fibre damage.

Histological patterns of muscle in infants with developmental brain abnormalities

The histology of muscle obtained from 23 hypotonic infants without neuromuscular disease is presented. Long-term follow-up neurological examinations were carried out to determine the site of the lesion. 18 cases have strong evidence of cerebral dysfunction, 12 of whom have histologial abnormalities of fiber-type distribution and diameter. Of the remaining five patients without obvious cerebral abnormality, four also had histological changes, but individual circumstances partially explain the cause of the abnormal histological patterns in these four. No single histological abnormality could be identified, but the results indicate that histological abnormalities of muscle in hypotonic infants without clinical or microscopic evidence of neuromuscular disease may be useful in predicting a cerebral cause for the hypotonia.