An investigation into the ultrastructural parameters of abdominal muscles in children and adolescents with spastic type cerebral palsy and the effect on postural muscle performance
Includes bibliographical references.Cerebral palsy (CP) is an abnormality in motor function and postural tone that usually occurs at an early age. Spastic type cerebral palsy (STCP) - the most common type of motor disorder - involves increased muscle tone, a rigid posture in the limbs and muscle weakness resulting in impairment of gross motor function, trunk instability and co-ordination. The management of CP cases includes a broad spectrum of therapeutic interventions, therefore involving a large multi-professional team, and providing an ideal opportunity for collaboration amongst professionals. The primary determinants of muscle function are the architectural parameters (MAP's) of the muscle which determine the macroscopic arrangement of muscle fibres relative to the axis of force generation. Ultrasonography was used to quantify these MAP's while the NORAXAN® electromyograph was used to monitor neuromuscular activity in children and adolescents with STCP (N = 63) and the results were compared with the findings from aged-matched individuals with typical development (TD), (N = 82). All the muscles - external oblique (EO), internal oblique (IO), transversus abdominis (TrA) and rectus abdominis (RA) - were thicker in the STCP group than in the TD group. The EO, IO and TrA muscles in the STCP group were thicker at rest than in individuals with TD. The MAP's of EO, IO and TrA in the STCP group decreased when the muscles changed from the resting to an active state, as opposed to increasing in the TD group. The four muscles of individuals with TD and the RA of the STCP group showed significant changes (p < 0.001) in the frequency of EMG activity between the resting and active states. With regards to pennation, the abdominal muscles could be regarded as a transition group of muscles, lying somewhere between pennated and non-pennated muscle bellies. The findings from this study revealed that the RA may be targeted during rehabilitation regimens in the provision of stability for the bony pelvis, however, the force generated by this muscle may not be sufficient for the maintenance of trunk stability without optimal support from the EO and IO. An elevated tone at rest in the EO and IO, coupled with unilateral activity of the RA may lead to mal-rotation of the bony pelvis. The gross motor function measure (GMFM), which tested the five main domains of activity in individuals with STCP was well aligned with the gross motor function classification system (GMFCS) Levels (disability status) but did not correlate with changes in MAP's or with changes in the frequency of EMG activity between resting and active states. The performance of daily activities by individuals with STCP may not be a reflection of the activity of a muscle. The physiological cost index (PCI) was performed as an outcome measure to determine and compare the level of energy consumption between the two groups. The participants with STCP consumed significantly more (p < 0.001) energy than the TD group. However, this test showed no association with MAP, EMG activity and the changes in these muscle parameters from resting to active states (rho ranged from -0.009 to 0.27 in the STCP group; rho ranging from - 0.423 to 0.199 in the TD group). The PCI may not be a useful test in determining the morphological transformation taking place in a muscle or muscle groups. The MAP's of the unaffected side of the abdominal muscles of the STCP individuals with hemiplegia showed similar characteristics to those of TD individuals. The STCP adversely affects the trunk musculature in a similar fashion to the limbs. Knowledge of the macroscopic arrangement of the abdominal muscles is important in the management of pelvic stability in individuals with STCP
