Anti-epileptic therapy and fatal chickenpox.
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Adolescent↗
Biomedical subjects
R V Williamson
Publications and source records attributed to R V Williamson.
Vibratory sensory testing in acute peripheral nerve compression.
Vibratory thresholds were continually measured with a variable-amplitude vibrometer during periods of controlled median nerve compression in 12 human volunteers. Tissue fluid pressure in the carpal canal was maintained at 50 mm Hg, a level which caused a complete loss of nerve function in all subjects by 45 minutes. In all subjects vibratory thresholds proved to be the earliest test indicating a decrease in nerve function. Semmes-Weinstein pressure testing and 256 cycles/sec vibratory sensibility correlated well with measurements of vibratory thresholds and with the electrodiagnostic testing. Static and moving two-point discrimination did not become abnormal until late in the clinical testing. The vibrometer has significant potential as a clinical and research instrument in nerve compression syndromes. This study supports the use of vibratory stimuli as a noninvasive diagnostic test; it is currently undergoing evaluation in a number of clinical studies.
Adult↗
Effects of increased systemic blood pressure on the tissue fluid pressure threshold of peripheral nerve.
This study was designed to evaluate the functional response of the median nerve at the wrist to various degrees of acute, local compression in hypertensive patients. After measuring resting tissue fluid pressure in the carpal tunnel of the nondominant hand of nine subjects (diastolic pressures of 90 mm Hg or greater), localized pressures of 50, 60, or 70 mm Hg were applied to the palmar aspect of the wrist. Motor and sensory latencies and amplitudes of the median nerve were evaluated before compression, during 30-240 min of compression, and during the postcompression recovery phase. Sensory responses were completely blocked at a threshold tissue fluid pressure of 60-70 mm Hg, measured by the wick catheter technique. This pressure threshold was greater than the 40-50 mm Hg previously found in normotensive subjects. The tissue pressure threshold of normotensive and hypertensive subjects was consistently 30 mm Hg below diastolic blood pressure (approximately 45 mm Hg below mean arterial blood pressure). These results support the concept that ischemia is the prime mechanism of conduction block in low pressure, nerve-compression syndromes.
Action Potentials↗
Sensibility testing in peripheral-nerve compression syndromes. An experimental study in humans.
Sensibility testing in peripheral-nerve compression syndromes was investigated in an experimental study in humans. Twelve volunteer subjects had controlled external compression of the median nerve at the carpal tunnel at a level of forty, fifty, sixty, and seventy millimeters of mercury. The subjects were then monitored for thirty to 240 minutes with four sensory tests: two-point discrimination, moving two-point discrimination, Semmes-Weinstein pressure monofilaments, and vibration. Sensory and motor conduction, subjective sensations, and motor strength were also continuously tested. The threshold tests (vibration and Semmes-Weinstein monofilaments testing) consistently reflected gradual decreases in nerve function in both subjective sensation and electrical testing, while the innervation density tests (two-point discrimination and moving two-point discrimination) remained normal until nearly all sensory conduction had ceased. Decreased muscle strength occurred late, and not until changes had already occurred in each of the sensory tests. Threshold tests of sensibility correlated accurately with symptoms of nerve compression and electrodiagnostic studies, and are being evaluated for clinical use in a variety of peripheral-nerve compression syndromes.
Action Potentials↗
Tissue pressure threshold for peripheral nerve viability.
To investigate the pressure threshold for peripheral nerve dysfunction in compression syndromes (carpal tunnel and compartment syndromes), carpal canal pressure was elevated to 40, 50, 60, and 70 mm Hg in normal volunteers. Motor and sensory latencies and amplitudes of the median nerve were evaluated before compression, after 30-240 minutes of compression, and during the postcompression recovery phase. Although some functional loss occurred at 40 mm Hg, motor and sensory responses were completely blocked at a threshold tissue fluid pressure of 50 mm Hg, measured by the wick catheter. In one subject in whom diastolic blood pressure was significantly higher than in other subjects, the threshold pressure was raised slightly. The Semmes-Weinstein monofilament test and the 256-cycle vibratory test were more sensitive than two-point discrimination tests for evaluating peripheral nerve function in this compression model. These results indicate that between 40 mm Hg and 50 mm Hg there exists a critical pressure threshold at which peripheral nerve is acutely jeopardized. Compartment decompression may not be indicated when interstitial pressures are below this level.
Action Potentials↗
Correlation of static to dynamic measures of lower extremity range of motion in cerebral palsy and control populations.
The question addressed in this study was whether static measurements of hip, knee, and ankle range of motion correlate to dynamic measurements of hip and knee function during gait. Range-of-motion measures of the lower extremities taken during physical examination (static variables) were recorded on 80 adolescents with cerebral palsy and 30 adolescent normal controls. Kinematic measurements collected during gait analysis (dynamic variables) were recorded on the same patients and controls. Results indicated no correlation greater than r = 0.50 (R2 < 0.25) between any static and dynamic variable for either group--cerebral palsy patients or controls. The lack of good correlation of these measures indicates static physical examination variables such as popliteal angle and straight-leg raise are not good predictors of dynamic gait, such as knee-extension and hip-flexion variables measured during ambulation in controls or cerebral palsy populations.
Adolescent↗
Partial physeal growth arrest: treatment by bridge resection and fat interposition.
Twenty-eight skeletally immature patients underwent 29 primary physeal bridge resections at Children's Hospital and Medical Center in Seattle, Washington. Twenty-two resections were followed for 2 years. There were 11 excellent, five good, two fair, and four poor results. Overall mean growth was 83% with 98% in the excellent group and 96% in the good group. Physeal bridge resection is an effective method of treating partial physeal growth arrest. Results with fat compare favorably with results of other interposition materials without the disadvantages of local reaction and implant removal.
Adipose Tissue↗