Neuromuscular maturation in the neonate: Combined electroneurographic and ultrasonographic study.

BACKGROUND: The combined electroneurography and muscle ultrasound examination (ENG-USM) in adult patients showed a correlation between the compound motor action potential (CMAP) and muscular thicknesses (MT). No similar studies exist regarding the neonatal period. AIM: To evaluate the correlations between the maximum compound muscle action potential (CMAP) and maximum muscle thickness (MT) in term and premature newborns versus a group of young adults, as measured by combined electroneurography-ultrasonography (ENG-USM) to assess the stages. STUDY DESIGN: Observational cohort study. SUBJECTS: We studied 36 subjects (14 premature and 11 term infants, and 11 young adults), who underwent ENG-USM of the tibialis anterioris (TA) muscle. OUTCOME MEASURES: We measured: 1) Onset-Peak (O-P) and Peak-to-Peak (P-P) maximum CMAP; 2) maximum MT; and 3) MT at the detected maximum CMAP. RESULTS: The maximum CMAP in term newborns studied was about 1/3 of the mean value measured in the adults; the differences between O-P and P-P values of the term versus premature infants were not significant. We did not find a good correlation between maximum MT and maximum CMAP in the term (r = 0.63) newborns, contrary to what was found in preterms (r = 0.95) and in young adults (r = 0.98). CONCLUSION: Our ENG-USM study shows that in newborns, the site of innervation of the neuromuscular plaque does not correspond to MT since muscle growth is related to the period of development, and depends on the progression of the nerve terminal branches that go to innervate the same muscle.

Peripheral nervous system maturation in preterm infants: longitudinal motor and sensory nerve conduction studies.

OBJECTIVE: To study the evolution of sensory-motor nerves in the upper and lower limbs in neurologically healthy preterm infants and to use sensory-motor studies to compare the rate of maturation in preterm infants at term age and full-term healthy neonates. METHODS: The study comprised 26 neurologically normal preterm infants born at 23-33 weeks of gestational age, who underwent sensory nerve conduction and motor nerve conduction studies from plantar medial and median nerves and from tibial and ulnar nerves, respectively. We repeated the same neurophysiological studies in 19 of the preterm infants every 2 weeks until postnatal term age. The data from the preterm infants at term was matched with a group of ten full-term babies a few days after birth. RESULTS: The motor nerve conduction velocity of the tibial and ulnar nerves showed progressive increases in values in relation to gestational age, but there was a decrease of values in distal latencies and F wave latencies. Similarly, there was a gradual increase of sensory nerve conduction velocity values of the medial plantar and median nerves and decreases in latencies in relation to gestational age. At term age, the preterm infants showed significantly lower values of conduction velocities and distal latencies than the full-term neonates. These results were probably because the preterm infants had significantly lower weights, total length and, in particular, distal segments of the limbs at term age. CONCLUSION: The sensory-motor conduction parameters were clearly related to gestational age, but extrauterine life did not affect the maturation of the peripheral nervous system in the very preterm babies who were neurologically healthy.

Do medical students' knowledge and attitudes about health and exercise affect their physical fitness?

This study examined the relationship between unselected first-year medical students' knowledge and attitudes about health or exercise and their personal physical fitness. The 131 subjects performed a maximal exercise test to determine physical fitness by measuring maximal oxygen consumption (VO2max), underwent hydrostatic weighing to assess body fat content (percent body fat), and completed a questionnaire to measure their knowledge and attitudes about health promotion/disease prevention and exercise. Many independent variables were significantly associated with VO2max in bivariate analyses, but only percent body fat, resting systolic blood pressure, and perceived barriers to health promotion/disease prevention and to exercise were significant predictors of VO2max (mL x kg-1 x min-1) in the multivariate analyses. The absolute VO2max (L x min-1) can be predicted from percent body fat, weight, and perceived barriers to health promotion/disease prevention. Freshmen medical students' attitudes toward health promotion/disease prevention and exercise constitute one of three strong predictors of physical fitness levels and should be determined, along with percent body fat and resting systolic blood pressure, when estimating fitness levels in a medical student population.