Sonja Mensch

57 Design and content validity INTRODUCTION Children with severe multiple disabilities (SMD) are characterized by a severe or profound intellectual disability and severe motor impairments. There is no universal description of this group to be found in the current literature. Apart from“severemultiple disabilities”, which we selected, the terms “severe generalized cerebral palsy”, “profound and intellectual multiple disability”, “severe motor and intellectual disability”, “severe neurological impairment and intellectual disability”are used. Support for these children in acquiring or improving motor abilities is highly relevant for participation in general care situations and a sense of self-determination or autonomy. Availability of practical and reliable instruments for the measurement of motor abilities in these children is very important. However, instruments specifically designed for the measurement of motor abilities in this target group are lacking. Children with SMD mostly have a level of motor abilities that is comparable to level IV/V of the Gross Motor Function Classification System (GMFCS) for children with cerebral palsy (Palisano et al. 1997) (Veugelers et al., 2005): they typically are wheelchair- bound and only a few are able to move by crawling or using a physical aid (Mensch, Rameckers, Echteld, & Evenhuis., 2015) (Mergler et al., 2012) (Rieken et al., 2011). They are usually severely limited in maintaining their body position or in transfers to another position. Communicative functions are highly limited; the children are only able to communicate non-verbally or through body language, which translates to Communication Function Classification System (CFCS) level V (Hidecker et al., 2011). The child handles objects with difficulty or has severely limited ability to perform even simple actions. It requires support in almost all situations, which corresponds to Manual Ability Classification System (MACS) levels III-IV (Eliasson et al., 2006). In addition, children with SMD are often diagnosed with sensory impairments, dysphagia often leading to respiratory infections (Calis et al. 2008), gastro-oesophageal reflux disease, epilepsy, scoliosis and contractures (Veugelers et al., 2010) (Liptak et al., 2001) (Calis, Olieman, Rieken, & Penning., 2007). As a result, these children are fully dependent on their caregivers and material in their immediate vicinity for all activities of daily life. In clinical practice, evaluation of motor abilities in children with SMD is often based on subjective assessments or on instruments developed for other target groups withmotor disabilities. An instrument for this specific group, with the aimof longitudinal evaluation of progression, stabilization, or deterioration of motor abilities, which could then be applied in clinical physical therapeutic practice, was needed. A systematic review of available instruments on motor abilities in children with severe disabilities (Mensch et al., 2015), showed that eight instruments might be potential candidates for application in children with SMD. One instrument (TDMMT) was developed specifically for this population (Putten van der, Vlaskamp, Reynders, &