‘Beckung and Kyllerman reply’

Abstract

‘Beckung and Kyllerman reply’ SIR–We are grateful for the valuable comments made by Dan et al.1 regarding our study on motor function in children with Angelman syndrome.2 We highly appreciate the additional information provided by Bernard Dan and Guy Cheron on advanced kinematic analysis comparing motor control in children developing normally with children with Angelman syndrome. In the clinical setting of our study we found that distal lower limb spasticity, ataxic-like gait, stiff lower limbs, and the presence of coactivation during locomotion were significantly more frequent in children with Angelman syndrome than in the comparison group of children with retardation of motor function from other causes. These results indicate that the physiology of pathological locomotion in children with Angelman syndrome is somewhat similar to that described in children with cerebral palsy (CP), and other upper motor-neuron syndromes. However, the dominant impression is of immaturity in execution, on a par with the generally low developmental level. As collaborators of the Surveillance of Cerebral Palsy in Europe (SCPE) network we apply the definition of CP as ‘a group of disorders, involving a disorder of movement and posture and of motor function, permanent but not unchanging, due to a non-progressive interference, lesion, and/or abnormality in the developing/immature brain’.3 In our opinion, motor problems in children with Angelman syndrome mainly represent immature dyscoordinated movement patterns, similar to those seen in the early stages of motor development. All children in this study functioned at a very immature gross and fine motor developmental level. We did also imply in our paper that the specific movement patterns were not purely immaturity. Signs of ataxia and spasticity were more prevalent in the Angelman syndrome group than the comparison group, which may indicate that there are additional dysfunctions specific to children with Angelman syndrome. We also found that the movement pattern was ataxic-like but differed from the dysmetria, dyssynergia, and dysequilibrium seen in individuals with cerebellar ataxia syndromes. Neurological abnormalities were mild, and, in our opinion, did not qualify for a diagnosis of CP. Difficulties experienced by children in the test probably resulted from central dyscoordination resulting in difficulties in positioning the body and interacting with the environment. Children seemed to have problems in sensory-motor integration, i.e. deficient interaction between multiple spinal and supraspinal systems. We considered that neurological abnormalities observed in children in our study with Angelman syndrome impeded motor function less than or as much as immaturity did. On the grounds mentioned above, the motor difficulties were insufficient for a diagnosis of spastic diplegic or ataxic CP, although mild neurological signs were present.