Neuropsychology of movement disorders and motor neuron disease

Abstract

Movement disorders fall into two broad categories: hypokinetic and hyperkinetic. Hypokinetic disorders involve a paucity of voluntary movement and are exemplified by Parkinson's disease and related parkinsonian disorders such as progressive supranuclear palsy and multiple system atrophy; in contrast, hyperkinetic disorders are characterized by excessive involuntary movements, a classic example of which is Huntington's disease (HD). These disorders all involve basal ganglia and/or cerebellum, and the cortical-basal ganglionic-thalamic-cortical pathophysiologies of the various disorders have been well described [1]. Motor neuron disorders are not classified as movement disorders. These disorders are grouped into upper and lower motor neuron disorders. Upper motor neuron disease is characterized by signs such as weakness, increased muscle tone, and hyperreflexia, whereas lower motor neuron disease is characterized by weakness, loss of reflexes, loss of muscle tone, fasciculations, and muscular atrophy. Although patients afflicted by motor neuron disease may have difficulty moving limbs due to weakness (for example, brushing their teeth due to upper extremity proximal weakness), they do not have a movement disorder per se. The best known motor neuron disease is amyotrophic sclerosis (ALS) or Lou Gehrig's disease. This chapter describes the more important movement and motor neuron disorders, specifically Parkinson's disease, progressive supranuclear palsy, essential tremor, Huntington's disease, and ALS and highlights the pathophysiology and neurobehavioral features of each condition. © 2010 Springer Science+Business Media, LLC.