Measurement of muscle thickness as quantitative muscle evaluation for adults with severe cerebral palsy

Abstract

Background and Purpose. The muscle strength of people with severe cerebral palsy (CP) is difficult to quantify because of cognitive and selective motor control problems. However, if muscle strength is related to muscle atrophy caused by activity limitation, quantitative morphological analysis such as analysis of muscle thickness (MTH), measured by ultrasound imaging, may be used to examine the muscle condition in daily use. The primary purpose of this investigation was to clarify the difference in MTH of several muscles by the motor functions used in daily activity in adults with CP with different levels of severity of involvement. The secondary purpose was to examine whether MTH is associated with age, body characteristics, and muscle spasticity. Subjects. Data were collected from a convenience sample of 25 adults with severe CP. Methods. The MTH of the biceps brachii (BB), quadriceps femoris (QF), triceps surae (TS), and longissimus (LO) muscles was measured with an ultrasound imaging device. The severity of the condition was classified with the Gross Motor Function Classification System (GMFCS), and functional status in sitting and standing was evaluated with a questionnaire administered to the staff assisting in the care of the subjects. Muscle spasticity was assessed with the Modified Ashworth Scale (MAS). Results. The MTH of the QF, LO, and TS showed significant differences according to the GMFCS level, and the MTH of the QF and LO differed significantly depending on functional status during activities of daily living. Age and body mass index showed no significant correlation with the MTH of any muscle. Body weight was correlated with the MTH of the BB and LO. The girth of the extremity was correlated only with the MTH of the BB. There was no relationship between MTH and MAS scores. Discussion and Conclusion. These results suggest that the MTH of the QF and LO differed significantly depending on the subjects' motor function during daily activity. The measurement of MTH may be an alternative method of quantitative muscle evaluation for people with severe CP for whom direct measurement of muscle strength is difficult.