++
INTRODUCTION TO MOVEMENT DISORDERS
++
In most realms of neurologic disease, localization is the first step toward differential diagnosis. In assessing movement disorders, however, the first step is to accurately characterize the type of abnormal movement(s) present, each of which has its own differential diagnosis. Movement disorders are broadly classified as either hyperkinetic (increased movement: tremor, chorea, myoclonus, dystonia, tics) or hypokinetic (decreased movement: bradykinesia as is seen in parkinsonism) (Table 23–1).
++
++
Tremor refers to rhythmic oscillation (i.e., shaking) of one or more parts of the body. Tremor can be characterized by (Table 23–2):
++
Body part(s) affected by tremor
Frequency: speed of oscillation of tremor
Amplitude: distance of excursion of tremor
The state(s) of the body part in which the tremor is observed—rest, posture, and/or action:
Rest tremor emerges when the affected body part is inactive
Postural tremor is observed when a posture is sustained against gravity (e.g., the arms and hands outstretched)
Kinetic or action tremor occurs with movement, and can be further characterized by whether the tremor is the same throughout the range of movement or worsens as the affected limb approaches a target (intention tremor).
++