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Biomedical subjects

S A Barron

Publications and source records attributed to S A Barron.

At least 19 recordsLinked to original sources
PubMed1994

Autonomic consequences of cerebral hemisphere infarction.

BACKGROUND AND PURPOSE: Recently, supraventricular tachycardia has been reported following right hemisphere stroke, suggesting a reduction in parasympathetic cardiac innervation after stroke of the right hemisphere. We performed power spectrum analysis of fluctuations in RR interval duration in the electrocardiogram in an attempt to determine how ischemic stroke influences autonomic cardiac innervation. METHODS: Power spectrum analysis of the variation in 256 consecutive electrocardiographic RR intervals was performed using the fast-Fourier transformation. The area under the spectral curve from 0 to 0.5 Hz and the area under the portion of the curve produced by parasympathetically mediated respiratory variations were determined in 20 patients with right-hemisphere and 20 patients with left-hemisphere ischemic stroke confirmed by computerized tomography. Data were compared with 40 age- and sex-matched healthy controls. RESULTS: Total cardiac autonomic innervation was reduced after a stroke of either hemisphere without regard to laterality. Cardiac parasympathetic innervation was reduced after stroke of either hemisphere with a significantly greater reduction after stroke on the right (P = 2.9 x 10(-5). CONCLUSIONS: Power spectral analysis of heart rate variability can detect autonomic consequences of stroke. The spectral data predict that, to the degree that cardiac arrhythmia is produced by unbalanced cardiac autonomic activity favoring the sympathetic system, such arrhythmias could be seen after stroke of either hemisphere and would be more common after cerebral infarction on the right. This is consistent with evidence from the recent literature.

Adult↗
PubMed1994

Parasympathetic autonomic neuropathy in diabetes mellitus: the heart is denervated more often than the pupil.

In one hundred subjects with diabetes mellitus assessed by the techniques of power spectral analysis of heart rate variability and heart rate variability during deep breathing, parasympathetic (vagal) cardiac denervation was shown to occur approximately twice as commonly as parasympathetic pupillary denervation measured by the maximal velocity of pupillary constriction. The pupillary dysfunction was detectable only when both tests of cardiac innervation were abnormal as well. No correlation was found between any of the autonomic measures and duration of known diabetes or degree of metabolic control.

Adolescent↗
PubMed1993

Vagal cardiovascular reflexes in young persons with syncope.

OBJECTIVE: To study the neurocardiologic reflexes in young persons who have fainted under conditions of emotional stress. DESIGN: Case-control study. SETTING: Clinical neurophysiology laboratory in Haifa, Israel. PATIENTS: Sixty persons (41 women and 19 men), 15 to 17 years old, who were referred for study because of syncope related to an emotionally distressing event. Forty aged-matched, healthy volunteers drawn from the same population served as controls. MEASUREMENTS: Resting electrocardiogram, inspiratory-expiratory difference in heart rate during deep breathing, heart rate response to the Valsalva maneuver, and blood pressure during motionless standing for 5 minutes. RESULTS: Although individual results were within widely accepted limits of normal, patients with syncope as a group had higher vagal autonomic tone than did controls. This manifested as a slower heart rate at rest (mean, 67.8 beats/min compared with 73.2 beats/min; P = 0.005), a higher inspiratory-expiratory difference in heart rate (mean, 44.1 beats/min compared with 37.9 beats/min; P = 0.001), and a higher Valsalva ratio (1.91 compared with 1.72; P < 0.0001). No significant difference was found in the PR and QTc (QT interval corrected for rate) intervals of the electrocardiogram or in the blood pressure response to standing. CONCLUSION: Many young persons who faint under conditions of emotional distress do so because a relatively high vagal tone predisposes them to the cardioinhibitory component of the syncope. Age-related physiologic reduction in vagal cardiac responses may explain the lower incidence of this type of syncope with increasing age.

Adolescent↗
PubMed1993

DC photoplethysmography in the evaluation of sympathetic vasomotor responses.

The d.c. component of the photoplethsmographic signal was used to determine the response of the finger vasculature to three standard tests of vasomotor function: (1) an inspiratory gasp (IG), (2) immersion of the contralateral hand in ice water (IW), and (3) the Valsalva manoeuvre. The vasoconstrictor response to the first two of these stimuli could be measured in all of 25 normal subjects. The response to the Valsalva manoeuvre could not be detected consistently. Seven patients with known sympathetic autonomic dysfunction showed no response to either IG or IW. In 30 patients with diabetes mellitus of over 10 years duration, 46.7% had no response to IG, and 20% had no response to IW. Absent responses correlated with abnormal autonomic cardiovascular reflexes, with absent sympathetic skin responses and with the severity of peripheral somatic neuropathy. The d.c. photoplethysmographic determination of the vasoconstrictor response in the finger after a deep inspiratory gasp and after ice water immersion offers an additional measure of the function of small (2 mu-6 mu) peripheral nerve fibres. Because of variability in the amplitude of the responses in normals, only an absent response should be accepted as abnormal.

Adult↗
PubMed1991

Muscle cramps associated with vincristine therapy.

The course of vincristine-induced neuropathy was evaluated in 14 patients who developed muscle cramps during chemotherapy. Cramps were noticed between 3 days and 4 months after the initiation of vincristine and following a cumulative dose of 1-9.4 mg/m2 (median 3.1 mg/m2). All patients reported daytime cramps and only 4 experienced nocturnal cramps. The lower extremities were involved in 11/14 and the upper extremities in 10/14 patients. Duration of cramps ranged from 1 to greater than 9 months. Physical examination revealed signs of peripheral neuropathy in all patients. Cramps were the first symptom of neurotoxicity in 4 patients. Other symptoms were noted in all patients, but only 3 had motor manifestations other than muscle cramps. Although symptoms of neuropathy tended to persist for several months, a rapid symptomatic improvement was noticed after withdrawal of vincristine. We conclude that vincristine-induced muscle cramps are not necessarily associated with severe neurotoxicity and should not automatically indicate interruption of therapy.

Adult↗
PubMed1988

Reflex sympathetic dystrophy syndrome coincident with acute diabetic neuropathy.

Diabetes mellitus and peripheral neuropathies are considered to be unusual causes of the reflex sympathetic dystrophy syndrome. Their coexistence in a patient with this syndrome is rare and considered to be incidental. We report a case in which remission of the syndrome accompanied the resolution of the diabetic neuropathy. A possible pathophysiologic mechanism connecting these conditions is discussed.

Bone Diseases, Metabolic↗
PubMed1987

Sympathetic cholinergic dysfunction in amyotrophic lateral sclerosis.

The results of evaluation of the autonomic nervous system of a patient with amyotrophic lateral sclerosis are presented. As previously reported, parasympathetic function and sympathetic adrenergic function were normal as assessed by cardiovascular reflexes. However, a disturbance in sympathetic cholinergic function as measured by the sympathetic skin response was demonstrated. We suggest that the latter test be included in all electrophysiological evaluations of autonomic function in amyotrophic lateral sclerosis.

Amyotrophic Lateral Sclerosis↗
PubMed1983

Abnormal spontaneous electrical activity and gross enlargement of muscle.

In a patient with congenital hypertrophy of the right leg, there developed progressive enlargement of the extremity and inflammatory pseudotumor and electrical myotonia within the enlarged muscle. In three other reported cases, progressive muscle enlargement was associated with abnormal spontaneous electrical and mechanical activity of muscle. In all four cases, the muscle enlargement was probably due to a combination of work hypertrophy secondary to the abnormal mechanical activity and stretch-induced hypertrophy of denervated muscle.

Adult↗