Classification and Approach to Movement Disorders

The term “movement disorder” refers to a heterogeneous group of conditions that result in abnormal form or timing of voluntary movement in individuals with normal strength and sensation. Movement disorders can be grouped into three general categories, hypokinetic, hyperkinetic, and ataxic. Hypokinetic movement disorders are characterized by tremors. Hyperkinetic movement disorders are characterized by involuntary movements that intrude into the normal flow of motor acts. Ataxic movement disorders are characterized by a lack of speed and skill in performing acts requiring the smoothly coordinated activity of several muscles.

Movement disorders are neurologic syndromes in which movement is either excessive (hyperkinesia) or too little (hypokinesia). A general term used for both hyperkinesia and hypokinesia is dyskinesia, which is defined as difficulty performing voluntary movements. The prototypic hypokinetic movement disorder is Parkinson disease (PD). Other terms used to describe this movement disorder are bradykinesia (slowness of movement) and akinesia (loss of movement).

Movement disorders are common in adult clinical practice. An important first step in evaluation and management of these disorders is identification of a potentially reversible cause, most commonly medication effect. All patients younger than 50 years presenting with any type of movement disorder should be evaluated for Wilson disease.

Movement disorders include syndromes characterized by either slowness and paucity of voluntary movement (hypokinetic disorders) or involuntary movements (hyperkinetic disorders). Both types of movement disorder can present as a clinical emergency, where prompt diagnosis and treatment are necessary to avoid morbidity or mortality. This chapter reviews the most common hypokinetic and hyperkinetic movement disorder emergencies encountered in the hospital and intensive care unit, emphasizing diagnostic workup and practical management. Hypokinetic emergencies include neuroleptic malignant syndrome, parkinsonism-hyperpyrexia syndrome, acute parkinsonism, and psychosis in Parkinson’s disease. Hyperkinetic emergencies include hemiballismus-hemichorea, autoimmune orobuccolingual dyskinesia, serotonin syndrome, posthypoxic and other types of myoclonus, and acute dystonia. Diagnosis of these disorders is nearly always based on clinical evaluation; rapid recognition often results in effective treatment and a good prognosis for recovery. Consequently, familiarity with diagnosis and management of movement disorder emergencies is both important and useful.

Clinical Aspects Dyskinesias are abnormal involuntary movements. The common dyskinesias include tics, chorea, tremor, dystonia, myoclonus, and hyperactivity (Table 1). Several other less common dyskinesias also are important to recognize. The diagnosis of the type of movement disorder is clinical. When the movements are episodic and not seen by the pediatrician, obtaining a home videotape is recommended. Most patients who have movement disorders, with the exception of tic disorders, should be referred to a neurologist, but it is important for the pediatrician to be able to identify them and to be informed on issues relevant to management. THE MOST COMMON DYSKINESIAS Tic disorders include motor (myoclonic and dystonic), vocal (phonic), and sensory tics. Tics may be simple or complex (Table 2). Myoclonic tics are jerks; dystonic tics are postures. Children who have vocal tics such as throat clearing, coughing, or sniffing may be referred to allergists or ear, nose, and throat specialists before the correct diagnosis is made. Sensory tics are peculiar sensations. Tics are increased by stress, decreased by activities that require concentration, exhibit a fluctuating pattern, and are less noticeable during sleep. The patient can suppress the movements or vocalizations voluntarily for minutes or hours, but then is unable to control the movements or the vocalizations.

Three hysterical movement disorders are reported: a case of hysterical bilateral blepharospasm which later presented as hysterical hemifacial spasm, a case of hysterical myoclonus, and a case of hysterical parkinsonism. Two patients presented with a relative indifference to preceding life experiences that would normally have evoked considerable emotion. Two of the cases first presented at an older age and one of these older patients was a man. Two of the patients agreed to hypnotherapy and supportive psychotherapy. In both cases the “involuntary” movements disappeared during hypnosis. In the third case, there was a complete spontaneous resolution of symptoms in a neurological condition where resolution would not be expected to occur.

Fifty-five patients underwent radiosurgical placement of lesions either in the thalamus (27 patients) or globus pallidus (28 patients) for treatment of movement disorders. Patients were evaluated pre- and postoperatively by a team of observers skilled in the assessment of gait and movement disorders who were blinded to the procedure performed. They were not associated with the surgical team and concomitantly and blindly also assessed a group of 11 control patients with Parkinson's disease who did not undergo any surgical procedures. All stereotactic lesions were made with the Leksell gamma unit using the 4-mm secondary collimator helmet and a single isocenter with dose maximums from 120 to 160 Gy. Clinical follow-up evaluation indicated that 88% of patients who underwent thalamotomy became tremor free or nearly tremor free. Statistically significant improvements in performance were noted in the independent assessments of Unified Parkinson's Disease Rating Scale (UPDRS) scores in the patients undergoing thalamotomy. Eighty-five and seven-tenths percent of patients undergoing pallidotomy who had exhibited levodopa-induced dyskinesias had total or near-total relief of that symptom. Clinical assessment indicated improvement of bradykinesia and rigidity in 64.3% of patients who underwent pallidotomy. Independent blinded assessments did not reveal statistically significant improvements in Hoehn and Yahr scores or UPDRS scores. On the other hand, 64.7% of patients showed improvements in subscores of the UPDRS, including activities of daily living (58%), total contralateral score (58%), and contralateral motor scores (47%). Ipsilateral total UPDRS and ipsilateral motor scores were both improved in 59% of patients. One (1.8%) of 55 patients experienced a homonymous hemianopsia 9 months after pallidotomy due to an unexpectedly large lesion. No other complications of any kind were seen. Follow-up neuroimaging confirmed correct lesion location in all patients, with a mean maximum deviation from the planned target of 1 mm in the vertical axis. Measurements of lesions at regular interals on postoperative magnetic resonance images demonstrated considerable variability in lesion volumes. The safety and efficacy of functional lesions made with the gamma knife appear to be similar to those made with the assistance of electrophysiological guidance with open functional stereotactic procedures. Functional lesions may be made safely and accurately using gamma knife radiosurgical techniques. The efficacy is equivalent to that reported for open techniques that use radiofrequency lesioning methods with electrophysiological guidance. Complications are very infrequent with the radiosurgical method. The use of functional radiosurgical lesioning to treat movement disorders is particularly attractive in older patients and those with major systemic diseases or coagulopathies; its use in the general movement disorder population seems reasonable as well.

The hyperkinetic movement disorders include heterogeneous diseases and syndromes, all characterized by one or a variety of excessive, involuntary movements. The hyperkinetic movement disorders are heterogeneous in clinical presentation, but a rational and practical approach to diagnosis exists based on new genetic correlations and targeted laboratory investigations. Treatments informed by a still-developing picture of motor pathophysiology offer significant benefit for these disorders. This chapter discusses choreiform disorders, including patterns in choreiform diagnosis; tremor disorders; paroxysmal disorders, including tics and myoclonus; dystonias, including monogenic primary dystonias; and pathophysiology and treatment in the hyperkinetic movement disorders. Figures include clinical photos, computed tomography scans, and an algorithm representing cortical-subcortical circuitry. Tables delineate definitions, distinguishing clinical features, medications, genetics, protein products, and treatments associated with various disorders.  This review contains 6 figures, 12 tables, and 145 references.