Movement disorders are a fascinating, heterogeneous group of neurologic conditions characterized by either an excess of movement (hyperkinetic movement disorders), a paucity of movement (hypokinetic movement disorders), or impaired control of motor functions (eg, cerebellar ataxia). Worthy of emphasis is the fact that, as with all clinical syndromes in medicine, both a thorough history, including pertinent positive and negative findings, and a careful examination are fundamental in establishing the correct diagnosis. On examination, movement disorders are diagnosed by first visually identifying the type of movement based on its characteristics (eg, tremor); this is called the phenomenology of the movement. A differential can then be generated based on history and examination findings. Appropriate neuroimaging and laboratory studies may also be helpful in establishing a diagnosis.
Hyperkinetic movement disorders include tics, tremor, chorea, dystonia, myoclonus, and stereotypy, all of which can be manifestations of various clinical syndromes. Hypokinetic movement disorders are much less common in children; the archetypal hypokinetic movement disorder is parkinsonism, of which the most common etiology in adults is Parkinson disease. Spasticity, a velocity-dependent increase in muscle tone, is, strictly speaking, not a movement disorder, although it can be present in patients who also have movement disorders (eg, patients with cerebral palsy) and can impair gait and motor control. The word dyskinesia, which simply means “abnormal movement,” is in and of itself not specific, and standing alone, it is not a particularly useful descriptor when identifying involuntary movements. However, when placed in context, it can convey the constellation of symptoms seen in distinct clinical syndromes (as in the case of paroxysmal kinesigenic dyskinesia or levodopa-induced dyskinesia).
When taking a history of movement disorders, it can be very helpful to ask the patient (or, more frequently, the parents) about the onset of symptoms in this way: “When was the very first time in your life that you ever experienced any abnormal movements?”
This chapter will address pertinent clinical entities in order to equip the pediatrician with tools to classify and evaluate them. Of course, any movement disorder that is associated with rapid progression, significant functional impairment, or cognitive decline necessitates prompt referral to a child neurologist, ideally to a pediatric movement disorders specialist, or, if the situation warrants, to the emergency department. Tics and stereotypy may not require referral, should the practitioner be confident of these diagnoses; in most other cases of involuntary movements (tremor, chorea, dystonia, myoclonus, parkinsonism), referral is often warranted.
HYPERKINETIC MOVEMENT DISORDERS
Tics and Tourette Syndrome
Tics are sudden, brief, intermittent, recognizable, repetitive movements or vocalizations that are almost always suppressible for short periods and are usually associated with a preceding urge to perform the movement or vocalization. Patients often describe this premonitory urge phenomenon as an unpleasant, often difficult-to-describe sensation that builds and then is resolved by the action for a period of time, ...