European consensus on the concepts and measurement of the pathophysiological neuromuscular responses to passive muscle stretch

BACKGROUND AND PURPOSE: To support clinical decision-making in central neurological disorders, a physical examination is used to assess responses to passive muscle stretch. However, what exactly is being assessed is expressed and interpreted in different ways. A clear diagnostic framework is lacking. Therefore, the aim was to arrive at unambiguous terminology about the concepts and measurement around pathophysiological neuromuscular response to passive muscle stretch. METHODS: During two consensus meetings, 37 experts from 12 European countries filled online questionnaires based on a Delphi approach, followed by plenary discussion after rounds. Consensus was reached for agreement ≥75%. RESULTS: The term hyper-resistance should be used to describe the phenomenon of impaired neuromuscular response during passive stretch, instead of for example 'spasticity' or 'hypertonia'. From there, it is essential to distinguish non-neural (tissue-related) from neural (central nervous system related) contributions to hyper-resistance. Tissue contributions are elasticity, viscosity and muscle shortening. Neural contributions are velocity dependent stretch hyperreflexia and non-velocity dependent involuntary background activation. The term 'spasticity' should only be used next to stretch hyperreflexia, and 'stiffness' next to passive tissue contributions. When joint angle, moment and electromyography are recorded, components of hyper-resistance within the framework can be quantitatively assessed. CONCLUSIONS: A conceptual framework of pathophysiological responses to passive muscle stretch is defined. This framework can be used in clinical assessment of hyper-resistance and will improve communication between clinicians. Components within the framework are defined by objective parameters from instrumented assessment. These parameters need experimental validation in order to develop treatment algorithms based on the aetiology of the clinical phenomena.status: publishe

Human fetal amino acid metabolism at term gestation

Background: Knowledge on human fetal amino acid (AA) metabolism, largely lacking thus far, is pivotal in improving nutritional strategies for prematurely born infants. Phenylalanine kinetics is of special interest as is debate as to whether neonates will adequately hydroxylate phenylalanine to the semiessential AA tyrosine. Objective: Our aim was to quantify human fetal phenylalanine and tyrosine metabolism. Design: Eight fasted, healthy, pregnant women undergoing elective cesarean delivery at term received primed continuous stable-isotope infusions of [1-C-13] phenylalanine and [ring-D-4] tyrosine starting before surgery. Umbilical blood flow was measured by ultrasound. Maternal and umbilical cord blood was collected and analyzed by gas chromatography-mass spectrometry for phenylalanine and tyrosine enrichments and concentrations. Data are expressed as medians (25th-75th percentile). Results: Women were in a catabolic state for which net fetal AA uptake was responsible for >= 25%. Maternal and fetal hydroxylation rates were 2.6 (2.2-2.9) and 7.5 (6.2-15.5) mu mol phenylalanine/(kg.h), respectively. Fetal protein synthesis rates were higher than breakdown rates: 92 (84-116) and 73 (68-87) lmol phenylalanine/(kg.h), respectively, which indicated an anabolic state. The median metabolized fraction of available phenylalanine and tyrosine in the fetuswas < 20% for both AAs. Conclusions: At term gestation, fetuses still show considerable net AA uptake and AA accretion [converted to tissue approximate to 12 g/(kg.d)]. The low metabolic uptake (AA usage) implies a very large nutritional reserve capacity of nutrients delivered through the umbilical cord. Fetuses at term are quite capable of hydroxylating phenylalanine to tyrosine. Am J Clin Nutr 2009; 89: 153-60