Cerebral palsy may be classified by the type of movement problem (such as spastic or athetoid cerebral palsy) or by the body parts involved (hemiplegia, diplegia, and quadriplegia). Spasticity refers to the inability of a muscle to relax, while athetosis refers to an inability to control the movement of a muscle. Infants who at first are hypotonic wherein they are very floppy may later develop spasticity. Hemiplegia is cerebral palsy that involves one arm and one leg on the same side of the body, whereas with diplegia the primary involvement is both legs. Quadriplegia refers to a pattern involving all four extremities as well as trunk and neck muscles. Another frequently used classification is ataxia, which refers to balance and coordination problems. The motor disability of a child with CP varies greatly from one child to another; thus generalizations about children with cerebral palsy can only have meaning within the context of the subgroups described above. For this reason, subgroups will be used in this book whenever treatment and outcome expectations are discussed. Most professionals who care for children with cerebral palsy understand these diagnoses and use them to communicate about a child’s condition.
As noted above, a useful method for making subdivisions is determined by which parts of the body are involved. Although almost all children with cerebral palsy can be classified as having hemiplegia, diplegia, or quadriplegia, there are significant overlaps which have led to the use of additional terms, some of which are very confusing. To avoid confusion, most of the discussion in his book will be limited to the use of these three terms. Occasionally such terms as paraplegia, double hemiplegia, triplegia, and pentaplegia may occasionally be encountered by the reader; these classifications are also based on the parts of the body involved. The dominant type of movement or muscle coordination problem is the other method by which children are subdivided and classified to assist in communicating about the problems of cerebral palsy. The component which seems to be causing the most problem is often used as the categorizing term. For example, the child with spastic diplegia has mostly spastic muscle problems, and most of the involvement is in the legs, but the child may also have a smaller component of athetosis and balance problems. The child with athetoid quadriplegia, on the other hand, would have involvement of both arms and legs, primarily with athetoid muscle problems, but such a child often has some ataxia and spasticity as well. Generally a child with quadriplegia is a child who is not walking independently. The reader may be familiar with other terms used to define specific problems of movement or muscle function terms such as: dystonia, tremor, ballismus, and rigidity. The words severe, moderate, and mild are also often used in combination with both anatomic and motor function classification terms (severe spastic diplegia, for example), but these qualifying words do not have any specific meaning. They are subjective words and their meaning varies depending on the person who is using them.