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Biomedical subjects

R R Young

Publications and source records attributed to R R Young.

At least 109 records · Page 6Linked to original sources
PubMed1976

The results to be expected from electrical testing in the diagnosis of myasthenia gravis.

The purpose of this study was to derive numerical data concerning the probability of diagnosing myasthenia gravis by electrical tests, employing repetitive stimulation of motor nerves. This was done by recording the compound muscle action potential (CMAP) from 80 patients with clear-cut myasthenia gravis, using a number of different, reportedly useful, testing techniques. In 95% of these patients, the diagnosis could be documented by the careful application of rather simple methods, providing several muscles, including a proximal one such as deltoid, were studied.

Action Potentials↗
PubMed1976

Physiological and pharmacological aids in the differential diagnosis of tremor.

Physiological and pharmacological studies of more than 150 patients with movement disorders are reported. Particular attention is paid to the differentiation of various types of tremor on the basis of rate, rhythm, and pattern of EMG activity in antagonistic muscles. The typical 'tremor-at-rest' of Parkinson's disease--3-7 Hz activity which alternates between antagonistic muscles--is suppressed, at least briefly, during voluntary activity, at which time typical 8--12 Hz 'physiological tremor' may be seen. Essential tremor and its familial or senile variants also have a characteristic EMG pattern during voluntary activity--5-8 Hz bursts of activity which are synchronous in antagonistic muscles. This type of tremor may also be present in patients with Parkinson's disease and in certain kinships with a Charcot-Marie-Tooth polyneuropathy. Other tremors in association with polyneuropathy ('neuropathic tremor') have different physiological characteristics. Myoclonus is of essentially two types ('positive' with EMG bursts and 'negative' with brief pauses in ongoing activity, as with asterixis) and may, at times, mimic tremor. Certain specific tremors respond predictably to specific pharmacological therapy.

Ataxia↗
PubMed1976

L-5-hydroxytryptophan in treatment of several different syndromes in which myoclonus is prominent.

The serotonin precursor L-5-hydroxytryptophan is useful therapy for patients with posthypoxic intention myoclonus. L-5-hydroxytryptophan plus carbidopa was administered to eight patients with this disorder or other syndromes in which myoclonus is prominent. This treatment (1) decreased the frequency of occurrence and amplitude of intention myoclonus in two patients with posthypoxic intention myoclonus and in one with idiopathic myoclonus, (2) had no effect in one patient with congenital encephalopathy and myoclonus, and (3) increased the frequency of occurrence and amplitude of myoclonus in two patients with lipid storage disease, one with myoclonic epilepsy, and in an additional patient with idiopathic myoclonus. Therefore, L-5-hydroxytryptophan does not effect improvement in all forms of myoclonus; it should be given with caution because it produces a high incidence of side effects. A patient's response to L-5-hydroxytryptophan therapy may be important in a diagnostic classification of myoclonic syndromes based on differences in indoleamine neurotransmitter function.

5-Hydroxytryptophan↗
PubMed1976

An evaluation of baclofen treatment for certain symptoms in patients with spinal cord lesions. A double-blind, cross-over study.

Baclofen (a gamma aminobutylic acid derivative) and a placebo were compared for their efficacy in relieving certain symptoms in patients with long-standing spinal cord lesions and "spinal spasticity." In a double-blind, cross-over clinical investigation, 22 patients with chronic spinal cord disease were studied. Baclofen regularly alleviated involuntary flexor or extensor spasms and increased resistance to passive movement of the legs but did not alter strength, gait, stretch reflexes, or clonus. Side effects were mild and transient. This study demonstrates that (1) baclofen is useful for the treatment of flexor spasms and (2) in evaluating a new mode of therapy, one must consider selectively the response of individual components of such global syndromes as "spasticity."

Adult↗
PubMed1975

Beta-adrenergic mechanisms in action tremor.

To study the mechanisms by which propranolol suppresses essential tremor, accelerometric recordings were made from four normal subjects and eight patients with that tremor, and small amounts of isoproterenol and propranolol were infused intravenously or into one brachial artery. Intra-arterial isoproterenol increased tremor amplitude selectively in that arm in normal subjects and in patients with essential tremor (range, 1.85 to 3.50 with mean 2.74 times the base-line level). Intra-arterial or intravenous propranolol quickly blocked the enhanced action tremor in both groups. It did not simultaneously affect the underlying essential tremor, whereas long-term oral propranolol therapy did diminish the amplitude of the essential tremor in each patient. Peripheral beta-adrenergic tremorogenic receptors function normally even in patients with essential tremor; their function is not necessary for the production of essential tremor, and the efficacy of chronic propranolol therapy in the suppression of essential tremor is not mediated via its peripheral beta-adrenergic blocking action.

Administration, Oral↗
PubMed1975

Pure pan-dysautonomia with recovery. Description and discussion of diagnostic criteria.

The patient described in this report appears to have had a unique, severe, pure pan-dysautonomia, and has been investigated in sufficient detail to specify precisely the disorders of functions subserved by the autonomic nervous system. Though we cannot rule out the possibility of an unknown autonomic toxin, we have no evidence for it and suggest that our patient's disorder be considered an acute polyneuritis, restricted to the autonomic system. Comment is made on tests of autonomic dysfunction and on the reliance which can be placed upon the results.

Blood Pressure↗
PubMed1975

EMG analysis of stereotyped voluntary movements in man.

EMG activity was recorded in biceps and triceps while subjects voluntarily flexed their elbows during a visual matching task. With fast flexion, the initial EMG was characterized by a triphasic pattern with a burst of activity first in biceps, then in triceps with a silent period in biceps, and finally in biceps again; these components were analysed quantitatively. Smooth flexion was characterized by continuous activity in biceps. Inhibition of tonic activity of triceps in relation to a fast flexion occurred in the 50 ms before the initiation of biceps activity. A patients with a severe pansensory neuropathy performed normally on these tasks. Physiological mechanisms underlying these patterns are analysed; an important conclusion is that the triphasic activity with fast flexion is 'centrally programmed'.

Adult↗
PubMed1975

EMG analysis of patients with cerebellar deficits.

EMGs from biceps and triceps were recorded during stereotyped elbow flexion tasks performed by 20 patients fulfilling clinical criteria for 'cerebellar deficits' and the data were compared with previously established normal standards. In a fast flexion task, 15 of 18 patients showed prolongation of the initial biceps and/or triceps components, and it is suggested that this abnormality might be an elemental feature of dysmetria. Ten of 14 patients showed the normal pattern of smooth flexion indicating that, with cerebellar deficits, smooth movements are better preserved than fast movements. The timing of the cessation of triceps activity before the initiation of biceps activity in an alternating movement was abnormal in 12 of 16 patients; this abnormality might be an elemental feature of dysdiadochokinesia.

Adolescent↗
PubMed1975

The effect of alcohol on essential tremor.

Five patients with essential tremor had a dramatic diminution in tremor amplitude within 15 minutes of ingesting small doses of ethyl alcohol. The same patients were given equivalent amounts of ethyl alcohol infused into a brachial artery, and there was no decrease in tremor amplitude in the perfused limb. It is concluded that, in patients with essential tremor, ethanol acts in a specific fashion on sensitive structures within the central nervous system and has no effect on peripheral tremorogenic mechanisms. This provides additional evidence for a central mechanism in essential tremor, distinguishing it from other tremors arising primarily from oscillation in peripheral servo-loops.

Administration, Oral↗