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Biomedical subjects

J C Stevens

Publications and source records attributed to J C Stevens.

At least 163 records · Page 9Linked to original sources
PubMed1978

Computed tomography and radionuclide imaging in the evaluation of ischemic stroke.

One hundred forty-one patients with cerebral or cerebellar infarction were examined by computed tomography (CT) as soon after the ictus as possible. The examination was repeated in 7 days, and a radionuclide brain scan was performed. The overall detection rate for ischemic infarction was approximately equal for both techniques, ranging from 58% for radionuclide scanning to 66% for the delayed CT. Almost half of the supratentorial infarcts examined by CT on the day of the ictus were demonstrated. Mass effect was observed as early as the first day and as late as the 25th day.

Adolescent↗
PubMed1978

Temperature-touch interaction: Weber's phenomenon revisited.

The six experiments reported here stemmed from Weber's (E. H. Weber, In R. Wagner (Ed.), Handwnörterbuch der Physiologie, 1846. Vol. 3, pp. 481-588) report that cold objects on the forehead feel heavier than warm ones, implying an effect of temperature on the touch modality. The experiments arrived at first-order answers to how temperature, force of stimulation, areal size of stimulation, and body locus might influence the magnitude of touch sensation. Typically, concomitant cooling greatly intensifies touch magnitude as perceived via the forehead and the forearm. Warning has little or no effect via the forehead but gives a significant intensification (less pronounced than that of cooling) on the forearm. When the areal size of the stimulation becomes very small, the intensification effects cannot be reliably demonstrated. The findings are reviewed in the light of what is known about the physiology of the cutaneous nerves.

Body Surface Area↗
PubMed1977

Punctate pressure sensitivity: effects of skin temperature.

The dependence on skin temperature of tactile sensitivity to punctiform (hair) stimulation of the finger tip came under study in five subjects. Their data show that punctate sensitivity is relatively stable over a wide range of thermal environments. On the average, some elevation of touch threshold occurred at a skin temperature of 20 degrees C (i.e., about 10 degree below normal), but severe loss of sensitivity first occurred at 10 degrees C. A small but possibly insignificant loss appeared at skin temperatures of 40 and 43 degrees C. The relatively stable behavior of the punctate threshold between about 20 and 40 degrees C contrasts with that of the vibrotactile threshold, which, at least for high frequencies, depends strongly on the skin temperature.

Adult↗
PubMed1976

Clinical vs quantitative evaluation of cutaneous sensation.

A comparison of the evaluation of cutaneous sensation by neurologic examination and by quantitative assessment in 107 patients with various neuromuscular disease has shown that there is a reasonably good correlation between the recognition of abnormalities of cutaneous sensation by clinical and by quantitative methods. Clinical neurologists tend to underestimate abnormalities of touch-pressure sensation. The quantitative evaluation of cutaneous sensation is useful in quality control of the clinical examination, in correlating the nature of sensation loss with the compound action potential and morphometry of biopsied nerve, in providing a score of sensation to follow the course and the effect of treatment protocols, and in monitoring for an adverse effect on sensation by an environmental or industrial poison. There is a good correlation between abnormality of touch-pressure sensation and loss of large myelinated fibers of sural nerve in neuropathy.

Adult↗
PubMed1976

Interaction of spatial and temporal summation in the warmth sense.

Two experiments explored the interaction of spatial and temporal summation in the perception of radiant heat. The first experiment showed that the absolute threshold for detecting two brief (0.1 sec) pulses of heat, one presented to each side of the forehead, is lower than the threshold for detecting a single pulse, even when the two pulses are separated in time by as muchas 0l75 sec. The second experiment showed that a single, 4-sec pulse of heat presented to one side of the forehead feels no warmer than two successive, 2-sec pulses, one to each side. Spatial and temporal summation appear to take place at least partly in the central nervous system.

Differential Threshold↗
PubMed1975

Frequency of nerve fiber degeneration of peripheral motor and sensory neurons in amyotrophic lateral sclerosis. Morphometry of deep and superficial peroneal nerves.

Among 10 patients with amyotrophic lateral sclerosis who had combined biopsy of muscle and cutaneous nerves, two had a history of paresthesia that suggested involvement of peripheral afferent neurons. Of four patients without paresthesia, two had unequivocal abnormalities of touch-pressure sensation of the toe. On morphometric evaluations of lateral fascicles of deep peroneal nerve, one nerve had an abnormally low myelinated fiber density and seven of 10 had abnormally high frequencies of teased-fiber abnormalities. Teased fibers in which myelin was degenerating into linear rows of myelin ovoids and balls occurred in 10.5 percent of fibers in amyotrophic lateral sclerosis nerves as compared with 1.7 percent in control nerves (0.01 less than p less than 0.025). Estimates of density of myelinated fibers were less sensitive than estimates of the frequency of various changes in teased fibers for detecting abnormality.

Aged↗