Median Motor Nerve Conduction and H-reflex Studies in Premature Infants

Many factors have been identified which to affect the rate of propagation of impulses along motor fibers. These include temperature changes around the nerve, diameter of the axon, degree of myelinization, age of infants, and local environment of the nerve. Motor nerve conduction velocity and Hoffman's reflex latency have been used to assess the degree of myelination and maturation of the nervous system. The conduction velocities in infants of a short gestational age are significantly lower than those of the fullterm infants. The extrauterine myelination and maturation might increase nerve conduction velocity. We measure the median motor nerve conduction velocity, compound muscle action potentials amplitude and H-reflex latency of premature infants to determine the neurological maturation after birth. The premature infants with gestational age above 37 weeks have a significantly higher conduction velocity and a shorter H-reflex latency than those of gestational age below 37 weeks. The premature infants with weight over 2.5 kg have a significantly higher conduction velocity, larger compound muscle action potentials amplitude and a shorter H-reflex latency than those of weight below 2.5 kg. And there is a statistically significant negative correlation of the H-reflex latency with the postmenstrual age. The determination of motor nerve conduction velocities and H-reflex latencies seem to be an additional method in assessing the degree of maturity in infants after birth.

Comparison of Sensitivity of Neurobehavioral Cognitive Status Examination and Mini-mental State Examination

The neurobehavioral cognitive status examination(NCSE), a screening examination tool that assesses cognitive funtion in a brief but quantitative fashion, is used as an independent test of five major areas: language, constructions, memory, calculation and reasoning. The examination also separately assesses levels of consciousness, orientation, and attention. This instrument quickly identifies the intact areas of functioning, yet provides more detailed assessment in the areas of dysfunction. To determine whether the neuro behavioral cognitive status examination is a more sensitive instrument for the detection of cognitive impairment than the minimental state examination(MMSE), we performed these test simultaneously in 26 patients with stroke. The sensitivities were 88.5% for NCSE and 53.8% for MMSE respectively. The sensitivity of NCSE was derived from two features of its design: the use of independent tests to assess skills within five major areas of cognitive functioning, and the use of graded tasks within each of these cognitive domains.

Skeletal Muscle Changes Following Injection of Local Anesthetics

To investigate the skeletal muscle changes, intramuscular injections of local anesthetics were performed using animal, Sprague-Dawley rat. The experiments were composed of two procedures, experiment I and II. In experiment I, single injection was performed using 0.4 cc of 1 and 2% of procaine and lidocaine. In experiment. II, repeated injection of 0.4 cc of 2% lidocaine on weekly bases 3 times were performed. The experimental rats were divided into five groups in five groups in experiment I: Four experimental group 40(10 rats for each local anesthetics) and Control 10 and were divided into two groups in experiment II: Experimental group 8 and Control 4. The muscle biopsies were performed in 15 minutes, 2, 4, 8 and 16 days after injection in two experiments. No muscle fiber changes were shown in control group, and 1~2% procaine, and 2% lidocaine injected groups of experiment I and control group of experiment II. In the groups of single and repeated injections of 2% lidocaine, muscular inflammatory changes were shown on 2 and 4 days after injection. The changes were more extensive in the group of repeated injections. The inflammatory reaction was usually abated on 8 days after injection and the muscles appeared to be normal in quality and quantity on 16 days after injection These histopathologic results indicated reversible muscular changes. Although the muscular changes are reversible after local anesthetics injection, the concentration of local anesthetics and injection interval should be considered to minimize the muscle fiber changes in the repeated injections.