The Muscle in Children With Cerebral Palsy - Longitudinal Exploration of Microscopic Muscle Structure.

Cerebral palsy (CP) is a motor impairment due to a brain malformation or a brain lesion before the age of two. Spasticity, hypertonus in flexor muscles, dyscoordination and an impaired sensorimotor control are cardinal symptoms. The brain lesion is non-progressive, but the flexor muscles of the limbs will during adolescence become relatively shorter and shorter (contracted), forcing the joints into a progressively flexed position. This will worsen the positions of already paretic and malfunctioning arms and legs. Due to bending forces across the joints, bony malformations will occur, worsening the function even further. Currently, the initial treatment of choice is the use of braces, which diminishes the shortening somewhat. Since about 25 years a combination treatment with intramuscular botulinum toxin injections, braces and training has had a tremendous and increasing popularity, although lasting long-term clinical advantage is not yet proven.

Muscle morphology of the biceps brachii and the gastrocnemius muscles:

• The hypothesis is that care as usual, i.e. training and splinting sessions with botulinum toxin as adjuvant treatment, will reduce (normalize) the expression of the fast fatigable myosin heavy chain MyHC IIx and increase the expression of developmental myosin, as a possible sign of growth. As the biceps in the arm is used irregularly and voluntarily, and the gastrocnemius is activated during automated gait, the adaptations of those muscles will be different. Methods: Baseline muscle biopsies: Percutaneous biopsies from the biceps brachii and the gastrocnemius muscles are taken just before the first intramuscular botulinum toxin injection is given. The doses and the intervals for the botulinum toxin treatment will follow clinical routines. Training of the leg and arm will after the injections be performed with the help of physiotherapists and occupational therapists. Biopsies 4-6 months, 12 months and 24 months after the first botulinum toxin injection: The exact same procedure as above will be performed, but the biopsies will be taken 2 cm distant, medial or lateral, from previous biopsy sites. The muscle specimens are snap frozen and stored at -80°C until analyzed. The expression of different myosin heavy chain (MyHC) isoforms is assessed by using the monoclonal antibodies (mAb) N2.261, mAb A4.840 against slow MyHC I, mAb F1.652 against embryonic MyHC, and mAb NCL-MHCn against fetal (=neonatal) MyHC)(Tiger, Champliaud et al. 1997; Wewer, Thornell et al. 1997). Satellite cells will be identified with mAb against N-CAM (neural cell adhesion molecule). The fibers are typed according to the content of MyHCs.

Significance: Children with cerebral palsy have a motor impairment and progressive contractures that we often treat late; when tendon and bony surgery are the only options to realign the joints. Our aim is to treat the muscles early, so that the contractures and the bony malformations won't occur in the first place. Training and splints, with botulinum toxin as adjuvant treatment, is a very popular regime with this aim, but the long-term effect on muscle tissue and function is not yet known. This study will elucidate the effect during a 2-year period, and no such studies have yet been published. More knowledge is warranted regarding the actual molecular process in the muscle leading to a contracture, and its relation to the constant communication with the injured central nervous system. This study will give answers that could result in new, early prophylactic treatment of joint movement restrictions and motor impairment in children with CP.