Biomedical subjects

K N Seneviratne

Publications and source records attributed to K N Seneviratne.

15 recordsLinked to original sources

PubMed1989

Non familial juvenile distal spinal muscular atrophy of upper extremity.

An uncommon variety of non familial, juvenile onset, spinal muscular atrophy with asymmetric distal upper extremity affection is described. One hundred and two patients with a one to 14 year follow up are analysed. Spinal muscular atrophies with a distal distribution are rare. However, in the past three decades, previously unrecognised varieties of neurogenic muscular atrophy have been described in Asia (Japan, India, Sri Lanka and Singapore) under a variety of names. These provide interesting data for discussion of Asian neurogenic muscular atrophies with distal affection, in the context of diseases of the motor neuron.

Adolescent↗

PubMed1984

Clinical correlation of urodynamic findings in patients with localized partial lesions of the spinal cord and cauda equina.

Urodynamic studies were undertaken in 70 patients with incomplete, confirmed, localized lesions involving the spinal cord and cauda equina, irrespective of clinically evident bladder disturbances. Both detrusor and urethral function were simultaneously evaluated and correlated with neurological deficits and symptoms of lower urinary tract dysfunction. It was evident that in those patients with localized spinal cord lesions, lower urinary tract disturbances were closely associated with disturbances of pinprick sensation. Clinically silent bladder and sphincter dysfunction was encountered in 14% of the patients, and the number of asymptomatic patients was significantly higher among those with upper motor neuron lesions. Incontinence was associated predominantly with conus lesions; however, the other symptoms had no relationship to the site of the lesion. Symptoms such as urgency, incontinence, and nocturnal incontinence were associated with detrusor hyperactivity, and urinary retention was associated with urethral overactivity and dyssynergia. The urodynamic findings could explain the pathogenesis of the symptoms in most instances, but were not necessarily related to them. It is concluded that the pathways subserving lower-urinary-tract function are closely associated with the pathways subserving pinprick sensation, and that a lesion along the spinal axis can affect the bladder, sphincter, or both in a variety of ways, thus leading to the widely variable clinical findings associated with neurogenic lower urinary tract dysfunction.

Adult↗

PubMed1983

Significance of detrusor compliance in patients with localized partial lesions of the spinal cord and cauda equina.

Detrusor compliance was measured by cystometry irrespective of any symptoms of lower urinary trace dysfunction in 70 patients with localized, partial, surgically treatable lesions of the spinal cord and cauda equina. Compliance was found to be normal in all patients with upper motor neuron lesions; reduced compliance was encountered only in those with lower motor neuron lesions. Reduced compliance was closely associated with lesions of the conus medullaris and with detrusor hyperreflexia, and it is therefore likely that the mechanism of compliance involves a significant neural component. Incontinence, particularly nocturnal incontinence, was encountered more frequently among those with reduced compliance than in those with normal compliance, whereas retention of urine was comparatively rare with reduced compliance.

Adult↗

PubMed1983

Detrusor hyperreflexia in neurogenic bladder disorders caused by localized partial lesions of the spinal cord and cauda equina.

In 70 patients studied by cystometry, detrusor hyperreflexia seen with localized partial lesions of the spinal cord and cauda equina could be differentiated into two types. In one type, in which the hyperreflexia was of a reflex nature and bladder compliance was unchanged, the detrusor contractility was described as compliant hyperreflexic. In the other type, in which the contractions were of a rhythmic nature and accompanied by reduced compliance, the contractility of the detrusor was described as noncompliant hyperreflexic. The compliant hyperreflexic contractions correlated well with signs of upper motor neuron disturbance, the noncompliant hyperreflexic contractions with lower motor neuron disturbance.

Adult↗

PubMed1974

Nodal gap substance in diabetic nerve.

Anoxia and KC1 have been used to inactivate peripheral nerves by depolarization conduction block. Investigation of the inactivation patterns in isolated sciatic nerves of healthy and alloxan-diabetic rats suggests that the paranodal gap substance of healthy nerve behaves as an effective periaxonal diffusion barrier. In diabetic nerve the permeability of this barrier is significantly increased. A marked reduction in the K' binding capacity of the nodal gap substance has been demonstrated in myelinated nerves of human diabetics and alloxan diabetic rats.

Animals↗

PubMed1973

Post-ischaemic paraesthesiae in diabetes mellitus.

A quantitative assessment of post-ischaemic paraesthesiae has been made in 50 diabetic subjects and in a group of healthy age-matched controls. The results show a highly significant diminution of the paraesthetic response in the diabetic subjects. The degree of depression of the paraesthetic response was associated with the duration of the disease and the severity of the metabolic abnormality as determined by the degree of insulin dependence. Diabetics with the juvenile onset type of the disease were more adversely affected than those with the maturity onset type. There was no consistent relationship between the degree of depression of the paraesthesiae and the presence of peripheral neuropathy. The significance of these results is discussed in relation to the factors which determine the composition of the ionic micro-environment of myelinated nerve and the level of electrical excitability of the nerve fibre.

Adult↗

PubMed1972

Effects of hyperkalaemia on the excitability of peripheral nerve.

An experimental animal model has been developed for the study of excitability change in peripheral nerve during limb ischaemia. This model has been used to investigate the effects of hyperkalaemia on the sequence of excitability change that occurs during cuff-induced limb ischaemia and in the post-ischaemic recovery period. The results lend support to the hypothesis that the dynamics of K ion concentration in the periaxonal space play a critical role in determining these excitability changes and that the polyanionic mucopolysaccharide gap substance of the node of Ranvier is likely to constitute the diffusion barrier that defines the periaxonal space.

Action Potentials↗

PubMed1972

Permeability of blood nerve barriers in the diabetic rat.

An albumin-Evans blue conjugate has been used as a fluorescent tracer to demonstrate the increased permeability of endoneurial capillaries and perineurial sheath of the sciatic nerve of the alloxan-diabetic rat. The significance of the extravasation of protein into the endoneurial space is discussed in relation to the altered dynamics of the endoneurial microcirculation. It is suggested that tissue hypoxia produced in this way may be a cause of the segmental demyelination which occurs in these nerves.

Animals↗

PubMed1970

The role of diffusion barriers in determining the excitability of peripheral nerve.

The excitability changes occurring in normal isolated peripheral nerves of rats have been studied during exposure to hypoxic and anoxic conditions before and after the administration of insulin. The changes observed have been explained in terms of the dynamics of K' equilibrium in the periaxonal spaces, and attention is drawn to the importance of the relative impermeability of the periaxonal diffusion barrier in determining this equilibrium. Isolated peripheral nerves from alloxan-diabetic rats, studied under similar conditions, show significant differences in the sequence of their excitability changes. It has been shown that the rate of change of excitability in these nerves is slower than those of control nerves. These results have now been interpreted in terms of the K' changes in the periaxonal space. It is concluded that these slower excitability changes are due to an increase in the permeability of the diffusion barrier of the diabetic nerve to potassium.

Animals↗

PubMed1970

Peripheral nerve function in chronic liver disease.

Peripheral nerve function has been studied in 50 patients with chronic liver disease. An increase in the latency or a reduction in the response amplitude of the evoked sensory potential of the median nerve was detected in 34 of the 50 subjects. This was in striking contrast to the paucity of neurological signs and symptoms suggestive of peripheral nerve damage seen in these patients. There was no evidence to show that alcohol was responsible for the neuropathy. Abnormalities in the excitability changes of sensory nerve during ischaemia were detected in seven of the 16 subjects whose distal sensory latencies were within normal limits. A critical evaluation of the hypotheses which have been postulated to account for the increased resistance of peripheral nerve to inactivation by ischaemia has been made. It is concluded that an increase of the permeability of the periaxonal diffusion barrier to K offers the most acceptable explanation for this phenomenon.

Adult↗

PubMed1969