Vitamin B12 for Asian immigrants.
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Biomedical subjects
Publications and source records attributed to M Swash.
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Muscle spindles have been studied in 7 autopsied cases of Duchenne muscular dystrophy. The autopsies of 2 boys of similar age who died without known neuromuscular disease were used as controls. The abnormalities found consisted of degenerative changes, atrophy and loss of intrafusal muscle fibres, thickening of the spindle capsule and widening of the periaxial space. In some very severely affected muscles there was evidence that spindles were destroyed in the course of the disease. Statistical comparison of these observations was made between the pathological and normal material. The muscle spindle innervation appeared normal in sectioned material. Teased preparations were not available for study.
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Two cases of encephalomyelitis are described in which the major clinical manifestation was muscular rigidity and stimulus-sensitive muscular spasms. It is suggested, from pathological evidence, that this rigidity was of spinal origin, and that this disorder is a rare but recognizable entity. Comparison is made with previously reported cases of rigidity of spinal origin, including encephalitis lethargica, and with 'subacute myoclonic spinal neuronitis' and the 'stiff man syndrome.'
In 15 patients with neurogenic muscular disorders, including cases of motor neuron disease, Wohlfart-Kugelberg-Welander disease, Davidenkow's scapuloperoneal syndrome, peripheral neuropathy and traumatic neuropathies, muscle biopsies were carried out, usually after EMG or single fibre EMG investigation. Enzyme histochemical and electronmicroscopic techniques were used to study longitudinal fibre splitting and its quantitative relation to the general changes in the biopsies. In 9 cases serial sections were used to study the longitudinal extent and character of fibre splitting. Longitudinal fibre splitting was found in 14 cases. It was prominent in Type 1 fibres, and in those biopsies in which hypertrophy was most marked. It was often associated with central migration of sarcolemmal nuclei. Ultrastructurally there was evidence that splitting consisted of mechanical disruption of the myofibrillar pattern, followed by an active process of membrane formation. We suggest that longitudinal splitting of muscle fibres, induced by overload of poorly innervated, hypertrophied fibres, can account for many of the "myopathic" changes found in neurogenic muscular disorders.
Two brothers with congenital myasthenia gravis are described. In both, ptosis and ophthalmoplegia responded poorly to oral anticholinesterase therapy and to thymectomy. The brothers had two different HLA haplotypes and neither had the HLA-A1-B8-DW3 haplotypes which are commonly associated with myathenia gravis in adult-onset cases.
An incidental finding during recordings from the median nerve was that the nerve trunk slides longitudinally in its bed when the limb is moved. The amount of movement has been measured in 19 subjects. The observations are discussed with reference to the pathology of entrapment neuropathies and it is suggested that, where longitudinal movement of a peripheral nerve is restricted, continual trauma results from normal movements of the limb.
The clinical significance of apparent pneumographic cerebellar atrophy has been studied in a group of 44 otherwise unselected patients found to have cerebellar atrophy, according to previously suggested criteria, at pneumoencephalography. Lateral and postero-anterior tomography of the posterior fossa was performed in all these cases. In each case the width of two or more sulci in the cerebellar vermis exceeded 2 mm. We have concluded that: (1) There is a relationship between the severity of pneumographic cerebellar atrophy and the severity of clinical signs of cerebellar disease (p = 0.03). (2) Severe or moderate atrophy of the vermis, whether generalized or focal, is usually associated with clinical signs of cerebellar disease, but mild atrophy of the vermis, equivalent to the "moderate" atrophy of previous studies, has no apparent diagnostic significance. (3) Atrophy of the cerebellar hemispheres, in the absence of atrophy of the vermis, is very unusual and it cannot, by itself, be correlated with clinical signs of cerebellar disease. (4) In individual cases, assessment of the significance of pneumographic cerebellar atrophy cannot be made without adequate clinical information.
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A myopathy, which improved with cyproheptadine hydrochloride therapy, developed in a patient with carcinoid syndrome of ten years' duration. Biopsy examination revealed advanced atrophy of type II muscle fibers, with type I fiber preponderance. Many of the small fibers had degenerated. Carcinoid myopathy may be due to excess circulating serotonin.
Abnormalities in the morphology and motor innervation of the muscle spindles are described in 4 autopsied cases of myasthenia gravis. There were changes consistent with motor denervation in 5 of 118 spindles examined in sectioned material. In 65 teased, silver-impregnated spindles there was proliferation of the fusimotor innervation due to axonal sprouting occurring in the endings themselves. Motor end-plates on the intrafusal muscle fibres showed "dystrophic" changes similar to those previously described in extrafusal muscle in this disease. The sensory innervation was normal. The possible signifance of these findings is discussed.
Studies of the extent and complexity of intrafusal muscle fibre splitting in myotonic dystrophy have been carried out in three spindles obtained at muscle biopsy, and in nine spindles found in the lumbrical muscle of a case that came to necropsy. It is suggested that splitting, due to mechanical stresses, leads to a regenerative response in the separated fragments.
A patient with scapuloperoneal atrophy of neurogenic type, in whome there was also distal sensory impairment, has been studied with conventional EMG, single fibre EMG, and muscle biopsy. This disorder, described by Davidenkow, may be a distinct entity.
In a patient with Holmes-Adie syndrome, and in another with tabes dorsalis, a transverse cord lesion resulted in a severe, but flaccid paraplegia with absent tendon reflexes. Flexor spasms were severe in both patients, but spasticity was absent. The significance of these observations is discussed in relation to the functional and anatomical disorder in these two syndromes.
The number and distribution of primary and secondary sensory endings has been studied in 52 de-efferentated baboon muscle spindles and the axon diameters of the afferent fibres innervating these endings have been measured. Each spindle contained a single primary sensory ending; most of these endings were supplied by a single afferent nerve fibre. Each primary sensory ending consisted of a multi-branched network distributed on both nuclear bag and nuclear chain fibres. Beaded sensory terminals were prominent in the central part of the ending. Eighty one secondary endings were found in 45 spindles (87% of the number of spindles remained). Of these endings, 70% were found in the S1 position, 25% in the S2 position and 4% in the S3 location. The afferent axons supplying the most equatorial of these endings were of thicker mean diameter than those supplying the most polar endings. In addition, the juxta-equatorial secondary endings were similar in form, although less regularly organized than the primary endings. The more polar secondary endings rarely fromed terminal sensory enlargements and usually took the form of a fine spray of unmyelinated branches. A non-parametric statistical comparison of physiological and anatomical data in baboon spindles has suggested that the demarcation criteria for separation of primary and secondary spindle afferents, using conduction velocity, should be modified. It is suggested that afferent fibres of conduction velocity less than 60 m/sec should be classified as secondary afferents, and fibres of conduction velocity greater than 72 m/sec should be classified as primary afferents.