Movement disorders arise from dysfunctional physiology within the motor and movement systems of the nervous system, and can involve multiple anatomic locations. A myriad of electrophysiologic manifestations can be detected in electromyography (EMG), electroencephalography (EEG), and other methods. Technical factors must be carefully considered and technical quality should be monitored throughout. Surface EMG provides the basis for the electrophysiologic examination of movement disorders. EEG is important for establishing cortical genesis as well as consciousness state determination during the movement disorder. Tremors of different etiologies may have different frequencies and activation characteristics that are best discovered on analysis of surface EMG characteristics. Also, classification of myoclonus physiology needs electrophysiologic testing. Proper myoclonus classification forms the best approach to symptomatic treatment strategy. Results from this testing provide important supplemental information, which can be used for a more exact diagnosis that leads to treatment.

Although movement is largely generated from the primary motor cortex, what movement to make and how to make it is influenced from the entire brain. External influences from the environment come from sensory systems in the posterior part of the brain, and internal influences, such as homeostatic drive and reward, from the anterior part. A movement is voluntary when a person’s consciousness recognizes it to be so because of proper activation of the agency network. Behavioral movement disorders can be understood as dysfunction of these mechanisms. Apraxia and task specific dystonia arise from disruption of parietal–premotor connections. Tics arise from a hyperactive limbic system. Functional movement disorders may also have an origin in abnormal limbic function and are believed to be involuntary due to dysfunction of the agency network. In Parkinson’s disease, bradykinesia comes from insufficient basal ganglia support to the anterior part of the brain.

The etiology of metabolic movement disorders is characterized by marked heterogeneity, including acquired and genetic forms (also known as inborn errors of metabolism). In both cases, metabolic alterations represent a possible pathogenetic mechanism of movement disorders that can present with dystonia, parkinsonism, choreoathetosis, or myoclonus, and can range from hyperacute to chronic forms. These conditions can be classified according to multiple aspects, such as etiology, age, or clinical features’ rapidity of onset. Understanding the underlying pathogenic mechanisms has led to specific treatments for acquired and genetic forms and prompt diagnosis is key to reducing brain damage and improving symptoms. Thus, this chapter offers an overview of these conditions’ main clinical and neuroradiologic features to help clinicians in the diagnostic process.

This chapter discusses the clinical approach to a patient with a movement disorder, based on the phenomenology of that particular disorder. It summarizes the definitions of the most prevalent movement disorders and highlights particular clinical aspects that may help narrow down the differential diagnosis.

The complexity of movement disorders poses challenges for clinical management and research. Functional imaging with PET or SPECT allows in-vivo assessment of the molecular underpinnings of movement disorders, and biomarkers can aid clinical decision making and understanding of pathophysiology, or determine patient eligibility and endpoints in clinical trials. Imaging targets traditionally include functional processes at the molecular level, typically neurotransmitter systems or brain metabolism, and more recently abnormal protein accumulation, a pathologic hallmark of neurodegenerative diseases. Functional neuroimaging provides complementary information to structural neuroimaging (e.g. anatomic MRI), as molecular/functional changes can present in the absence of, prior to, or alongside structural brain changes. Movement disorder specialists should be aware of the indications, advantages and limitations of molecular functional imaging. An overview is given of functional molecular imaging in movement disorders, covering methodologic background information, typical molecular changes in common movement disorders, and emerging topics with potential for greater future importance.

Secondary dystonia comprises a group of diverse dystonia syndromes, including hereditary diseases with a clinical phenotype exceeding dystonia as well as acquired dystonia. The first step in the classification of dystonic symptoms should be according to its clinical characteristics – age at onset, body distribution, temporal pattern and associated features. Limb dystonia in adulthood, as well as craniocervical dystonia presentation in childhood and young adolescence, point away from primary dystonia causes. Associated clinical features such as oculomotor disturbances, parkinsonism, cognitive and neuropsychiatric symptoms, and systemic involvement can be instructive for identifying the underlying dystonia syndrome. The diagnostic workup in patients with secondary dystonia depends on the suspected dystonia syndrome and can include laboratory tests in serum and cerebrospinal fluid (CSF), magnetic resonance (MR) imaging, genetic testing, etc. It is important to identify potential treatable causes, e.g., dopa-responsive dystonia, Wilson’s disease, Niemann–Pick Type C, infectious and autoimmune diseases, etc. Symptomatic treatments are also available.

Dystonia, defined as a movement disorder characterized by sustained or intermittent muscle contractions causing abnormal, often repetitive, movements, postures, or both, results in patterned, twisted, and sometimes tremulous movements. When dystonia is the sole manifestation, it is known as primary dystonia. Primary dystonia is an uncommon disorder and includes genetic forms of dystonia as well as idiopathic dystonia. Dystonia can involve one body part, when it is called focal; more than one contiguous body part, when it is known as segmental; or involving the trunk and more than two body parts, when it is called generalized. This chapter reviews primary dystonia: the epidemiology, the current theories of pathophysiology, the clinical description, and available treatments of genetic as well as the various forms of focal dystonia, including blepharospasm, oromandibular dystonia, laryngeal dystonia, cervical dystonia, focal hand dystonia and truncal dystonia.

Extrapyramidal symptoms are movement disorders associated with antipsychotics and include acute dystonias, akathisia, Parkinsonism, tardive dyskinesia, and neuroleptic malignant syndrome. Antipsychotic-related Parkinsonism and akathisia are the most commonly encountered antipsychotic related movement disorders. Tardive dyskinesia occurs with long-term antipsychotic use and can be very impactful on quality of life. Treatment options exist for those with tardive dyskinesia dependent on antipsychotics.

What neurotransmitter system is routinely influenced by both antipsychotics and stimulants?

Cerebral palsy is not a specific disease, but a clinical syndrome caused by a non-progressive injury to the developing brain that results in a disorder of movement and posture that is permanent but not unchanging. Spasticity is the most common movement disorder, affecting between 60% and 80% of children with cerebral palsy, and can manifest as spastic hemiplegia, spastic diplegia and spastic quadriplegia. Dystonia is characterized by involuntary sustained or intermittent muscle contractions that cause twisting and repetitive movements, abnormal postures or both. Athetosis, or intermittent writhing movement, is also very common. These movement disorders are all amenable to treatment with botulinum neurotoxin (BoNT). This chapter discusses topographical symptom distribution and illustrates the typical forms of cerebral palsy using an anatomical approach to management. Common clinical patterns of spastic posturing, the major involved, muscles and dose ranges for the different toxin preparations are tabulated.

In 1980, Alan B Scott published the use of botulinum neurotoxin type A by injection into extraocular muscles for treatment of strabismus. Use in blepharospasm was published in 1985, and cervical dystonia in 1986, followed by hemifacial spasm and other dystonias, including spasmodic dysphonia, hand dystonia, and conditions such as limb spasticity.

Formulations of neurotoxin type A worldwide include: Botox/onabotulinumtoxinA, Dysport/abobotulinumtoxinA, Xeomin/incobotulinumtoxinA, and a Chinese product marketed under various brand names in Asia. Botulinum neurotoxin type B is marketed as Neurobloc/Myobloc, or rimabotulinumtoxinB. PrabotulinumtoxinA and daxibotuinumtoxinA-Ianm are type A toxins under development.

Movement disorders are rarely medical emergencies or reason for evaluation in the emergency department (ED). However, they may be seen, and range from the familiar parkinsonism and drug-induced dystonia to rare disabling hemiballism secondary to a stroke. Movement disorders are typically a sign of an underlying neurological or nonneurological disorder, rather than the primary diagnosis. They can be strange in appearance and are often misdiagnosed as being hysterical or psychiatric in origin. In the ED, movement disorders are diagnosed based on a history and physical examination, with relatively few contributions from laboratory and radiographic studies.

In this chapter we describe different types of movement disorders that associate with autoimmune encephalitis, and the antibodies more frequently involved. In children the most common disorders are Sydenham chorea and anti-NMDAR encephalitis. Abnormal movements occur in ~80% of patients with anti-NMDAR encephalitis and include multiple different types such as chorea, oromandibular dystonia, stereotypies, opistotonus, catatonia, or myorhythmia. Children who develop anti-NMDAR encephalitis as a complication of previous herpes simplex viral encephalitis present prominent generalized chorea or choreoathetosis. In adults the most frequent autoimmune neurological disease that associates with movement disorders is anti-IgLON5 disease. More than 80% of patients this disease develop at least one type of movement disorder; gait instability or ataxia associated with craniofacial dyskinesias or generalized chorea are the most common combination of movement disorders. Hyperekplexia is a major manifestation of progressive encephalomyelitis with rigidity and myoclonus (PERM), which is usually associated with glycine receptor antibodies; some patients with similar symptoms have DPPX antibodies. Autoimmune chorea in adults may also be a paraneoplastic manifestation of small-cell lung cancer and CRMP5 antibodies. The most common paroxysmal abnormal movement of autoimmune origin is faciobrachial dystonic seizures associated with LGI1 antibodies. Patients with anti-CASPR2 encephalitis may have paroxysmal episodes of cerebellar ataxia that precede the encephalitis. Anti-CASPR2 encephalitis can also cause orthostatic myoclonus.