27. Movement disorders

Movement disorders are neurological disorders in which patients involuntarily move ‘too little’, as in Parkinson’s disease (PD), or on the other hand ‘too much’, as in dystonia. As explained in Chap. 4 and 5, movement is ultimately controlled by the corticospinal tract (pyramidal tract). Before a movement is performed, however, extensive preparation takes place, and the movement is constantly monitored to see if it is as intended. The cerebellum and basal nuclei play a key part in this. Cerebellar disorders were covered in the previous chapter. In this chapter we discuss the disorders that are traditionally classified as diseases of the basal nuclei. Extrapyramidal disorders are caused by abnormalities in the mesencephalon and basal ganglia. There are two forms of parkinsonism – typical (PD) and atypical. PD, the most common chronic disease of the central nervous system in individuals over the age of 50, always causes more than just motor symptoms. Clinical criteria are used to reach a diagnosis. Structural and functional imaging may be needed to distinguish the various forms of atypical parkinsonism from PD itself. There are good treatments available for Parkinson’s disease, and a multidisciplinary approach is required. Atypical parkinsonian disorders include vascular parkinsonism, drug-induced parkinsonism, multiple system atrophy, progressive supranuclear palsy and corticobasal degeneration. Parkinsonism is not the only extrapyramidal symptom, the others are tremor, chorea, ballism, myoclonus, tics, and dystonia. This chapter builds on our basic understanding of movement control, which was explained in Chap. 5. The main movement disorders are covered, with a focus on typical disorders, as characterized by parkinsonism or PD (sect. 27.1). With regard to this disorder, there is a detailed exploration of clinical features (particularly the distinction between motor and non-motor symptoms (sect. 27.1.1 and 27.1.2), current views on pathophysiology (sect. 27.1.4), reaching a diagnosis (sect. 27.1.5), and treatment options in the early and late stages (sect. 27.1.6). The much rarer atypical forms – the various Parkinson-plus syndromes – are briefly discussed in sect. 27.2. The various hyperkinetic movement disorders (tremor, dystonia, myoclonus, chorea, and tics) are dealt with in sect. 27.3. Several rules of thumb are provided, as an aid to diagnosing these disorders. The chapter concludes with a discussion of the various forms of deep brain stimulation that can be used to treat patients whose movement disorders have not responded adequately to drug treatment (sect. 27.4).