Although not necessary for the diagnosis, individuals with intellectual disability are at higher risk for SMD. It is more common in boys, and can occur at any age.

A stereotypy (, or ) is a repetitive or ritualistic movement, posture, or utterance. Stereotypies may be simple movements such as body rocking, or complex, such as self-caressing, crossing and uncrossing of legs, and marching in place. They are found in people with intellectual disabilities, autism spectrum disorders, tardive dyskinesia and stereotypic movement disorder, but may also be encountered in neurotypical individuals as well. Studies have shown stereotypies associated with some types of schizophrenia. Frontotemporal dementia is also a common neurological cause of repetitive behaviors and stereotypies. Several causes have been hypothesized for stereotypy, and several treatment options are available.

Stereotypy is sometimes called "stimming" in autism, under the hypothesis that it self-stimulates one or more senses. Related terms include "punding" and "tweaking" to describe repetitive behavior that is a side effect of some drugs.

Among people with frontotemporal lobar degeneration, more than half (60%) had stereotypies. The time to onset of stereotypies in people with frontotemporal lobar degeneration may be years (average 2.1 years).

Tourette syndrome is found among all social, racial and ethnic groups and has been reported in all parts of the world; it is three to four times more frequent among males than among females. The tics of Tourette syndrome begin in childhood and tend to remit or subside with maturity; thus, a diagnosis may no longer be warranted for many adults, and observed prevalence rates are higher among children than adults. As children pass through adolescence, about one-quarter become tic-free, almost one-half see their tics diminish to a minimal or mild level, and less than one-quarter have persistent tics. Only 5 to 14% of adults experience worse tics in adulthood than in childhood.

Up to 1% of the overall population experiences tic disorders, including chronic tics and transient tics of childhood. Chronic tics affect 5% of children, and transient tics affect up to 20%. Prevalence rates in special education populations are higher.

The reported prevalence of TS varies "according to the source, age, and sex of the sample; the ascertainment procedures; and diagnostic system", with a range reported between .4% and 3.8% for children ages 5 to 18. Robertson (2011) says that 1% of school-age children have Tourette's. According to Lombroso and Scahill (2008), the emerging consensus is that .1 to 1% of children have Tourette's, with several studies supporting a tighter range of .6 to .8%. Bloch and Leckman (2009) and Swain (2007) report a range of prevalence in children of .4 to .6%, Knight et al. (2012) estimate .77% in children, and Du et al. (2010) report that 1 to 3% of "Western" school-age children have Tourette's.

Singer (2011) states the prevalence of TS in the overall population at any time is .1% for impairing cases and .6% for all cases, while Bloch and colleagues (2011) state the overall prevalence as between .3 and 1%. Robertson (2011) also suggests that the rate of Tourette's in the general population is 1%. Using year 2000 census data, a prevalence range of .1 to 1% yields an estimate of 53,000–530,000 school-age children with Tourette's in the US, and a prevalence estimate of .1% means that in 2001 about 553,000 people in the UK age 5 or older would have Tourette's.

Tourette syndrome was once thought to be rare: in 1972, the US National Institutes of Health (NIH) believed there were fewer than 100 cases in the United States, and a 1973 registry reported only 485 cases worldwide. However, multiple studies published since 2000 have consistently demonstrated that the prevalence is much higher than previously thought. Discrepancies across current and prior prevalence estimates come from several factors: ascertainment bias in earlier samples drawn from clinically referred cases, assessment methods that may fail to detect milder cases, and differences in diagnostic criteria and thresholds. There were few broad-based community studies published before 2000 and until the 1980s, most epidemiological studies of Tourette syndrome were based on individuals referred to tertiary care or specialty clinics. Individuals with mild symptoms may not seek treatment and physicians may not confer an official diagnosis of TS on children out of concern for stigmatization; children with milder symptoms are unlikely to be referred to specialty clinics, so prevalence studies have an inherent bias towards more severe cases. Studies of Tourette syndrome are vulnerable to error because tics vary in intensity and expression, are often intermittent, and are not always recognized by clinicians, patients, family members, friends or teachers; approximately 20% of persons with Tourette syndrome do not recognize that they have tics. Newer studies—recognizing that tics may often be undiagnosed and hard to detect—use direct classroom observation and multiple informants (parent, teacher, and trained observers), and therefore record more cases than older studies relying on referrals. As the diagnostic threshold and assessment methodology have moved towards recognition of milder cases, the result is an increase in estimated prevalence.

Tourette's is associated with several comorbid conditions, or co-occurring diagnoses, which are often the major source of impairment for an affected child. Most individuals with tics do not seek medical attention, so epidemiological studies of TS "reflect a strong ascertainment bias", but among those who do warrant medical attention, the majority have other conditions, and up to 50% have ADHD or OCD.

Punding is a term that was coined originally to describe complex prolonged, purposeless, and stereotyped behavior in chronic amphetamine users; it was later described in Parkinson's disease. Punding is a compulsion to perform repetitive mechanical tasks, such as sorting, collecting, or assembling and disassembling common items. Punding may occur in individuals with Parkinson's disease treated with dopaminergic agents such as L-DOPA.

Tweaking is a slang term for compulsive or repetitive behavior; it refers to someone exhibiting pronounced symptoms of methamphetamine or amphetamine use.

Tourette syndrome is a spectrum disorder—its severity ranges over a spectrum from mild to severe. The majority of cases are mild and require no treatment. In these cases, the impact of symptoms on the individual may be mild, to the extent that casual observers might not know of their condition. The overall prognosis is positive, but a minority of children with Tourette syndrome have severe symptoms that persist into adulthood. A study of 46 subjects at 19 years of age found that the symptoms of 80% had minimum to mild impact on their overall functioning, and that the other 20% experienced at least a moderate impact on their overall functioning. The rare minority of severe cases can inhibit or prevent individuals from holding a job or having a fulfilling social life. In a follow-up study of thirty-one adults with Tourette's, all patients completed high school, 52% finished at least two years of college, and 71% were full-time employed or were pursuing higher education.

Regardless of symptom severity, individuals with Tourette's have a normal life span. Although the symptoms may be lifelong and chronic for some, the condition is not degenerative or life-threatening. Intelligence is normal in those with Tourette's, although there may be learning disabilities. Severity of tics early in life does not predict tic severity in later life, and prognosis is generally favorable, although there is no reliable means of predicting the outcome for a particular individual. The gene or genes associated with Tourette's have not been identified, and there is no potential "cure". A higher rate of migraines than the general population and sleep disturbances are reported.

Several studies have demonstrated that the condition in most children improves with maturity. Tics may be at their highest severity at the time that they are diagnosed, and often improve with understanding of the condition by individuals and their families and friends. The statistical age of highest tic severity is typically between eight and twelve, with most individuals experiencing steadily declining tic severity as they pass through adolescence. One study showed no correlation with tic severity and the onset of puberty, in contrast with the popular belief that tics increase at puberty. In many cases, a complete remission of tic symptoms occurs after adolescence. However, a study using videotape to record tics in adults found that, although tics diminished in comparison with childhood, and all measures of tic severity improved by adulthood, 90% of adults still had tics. Half of the adults who considered themselves tic-free still displayed evidence of tics.

Many people with TS may not realize they have tics; because tics are more commonly expressed in private, TS may go unrecognized or undetected. It is not uncommon for the parents of affected children to be unaware that they, too, may have had tics as children. Because Tourette's tends to subside with maturity, and because milder cases of Tourette's are now more likely to be recognized, the first realization that a parent had tics as a child may not come until their offspring is diagnosed. It is not uncommon for several members of a family to be diagnosed together, as parents bringing children to a physician for an evaluation of tics become aware that they, too, had tics as a child.

Children with Tourette's may suffer socially if their tics are viewed as "bizarre". If a child has disabling tics, or tics that interfere with social or academic functioning, supportive psychotherapy or school accommodations can be helpful. Because comorbid conditions (such as ADHD or OCD) can cause greater impact on overall functioning than tics, a thorough evaluation for comorbidity is called for when symptoms and impairment warrant.

A supportive environment and family generally gives those with Tourette's the skills to manage the disorder. People with Tourette's may learn to camouflage socially inappropriate tics or to channel the energy of their tics into a functional endeavor. Accomplished musicians, athletes, public speakers, and professionals from all walks of life are found among people with Tourette's. Outcomes in adulthood are associated more with the perceived significance of having severe tics as a child than with the actual severity of the tics. A person who was misunderstood, punished, or teased at home or at school will fare worse than children who enjoyed an understanding and supportive environment.

Hypokinesia refers to decreased bodily movement. One of the two categories of movement disorders, hypokinesia is characterized by a partial or complete loss of muscle movement due to a disruption in the basal ganglia. Patients with hypokinetic disorders like Parkinson's disease experience muscle rigidity and an inability to produce movement. It is also associated with mental health disorders and prolonged inactivity due to illness, amongst other diseases.

The other category of movement disorder resulting from damage to the basal ganglia, hyperkinesia, features an exaggeration of unwanted motion, like twitching or writhing in Huntington's disease or Tourette syndrome.

Developmental verbal dyspraxia is a developmental inability to motor plan volitional movement for the production of speech in the absence of muscular weakness. Research has suggested links to the FOXP2 gene.

Prognosis depends on the severity of the disorder. Recognizing symptoms early can help reduce the risk of self-injury, which can be lessened with meditations. Stereotypic movement disorder due to head trauma may be permanent.

Treatment of tics present in conditions such as Tourette’s syndrome begins with patient, relative, teacher and peer education about the presentation of the tics. Sometimes, pharmacological treatment is unnecessary and tics can be reduced by behavioral therapy such as habit-reversal therapy and/or counseling. Often this route of treatment is difficult because it depends most heavily on patient compliance. Once pharmacological treatment is deemed most appropriate, lowest effective doses should be given first with gradual increases. The most effective drugs belong to the neuroleptic variety such as monoamine-depleting drugs and dopamine receptor-blocking drugs. Of the monoamine-depleting drugs, tetrabenazine is most powerful against tics and results in fewest side effects. A non-neuroleptic drug found to be safe and effective in treating tics is topiramate. Botulinum toxin injection in affected muscles can successfully treat tics; involuntary movements and vocalizations can be reduced, as well as life-threatening tics that have the potential of causing compressive myelopathy or radiculopathy. Surgical treatment for disabling Tourette’s syndrome has been proven effective in cases presenting with self-injury. Deep Brain Stimulation surgery targeting the globus pallidus, thalamus and other areas of the brain may be effective in treating involuntary and possibly life-threatening tics.

There are many potential causes of dysarthria. They include toxic, metabolic, degenerative diseases, traumatic brain injury, or thrombotic or embolic stroke.

Degenerative diseases include parkinsonism, amyotrophic lateral sclerosis (ALS), multiple sclerosis, Huntington's disease, Niemann-Pick disease, and Friedreich ataxia.

Toxic and metabolic conditions include: Wilson's disease, hypoxic encephalopathy such as in drowning, and central pontine myelinolysis.

These result in lesions to key areas of the brain involved in planning, executing, or regulating motor operations in skeletal muscles (i.e. muscles of the limbs), including muscles of the head and neck (dysfunction of which characterises dysarthria). These can result in dysfunction, or failure of: the motor or somatosensory cortex of the brain, corticobulbar pathways, the cerebellum, basal nuclei (consisting of the putamen, globus pallidus, caudate nucleus, substantia nigra etc.), brainstem (from which the cranial nerves originate), or the neuro-muscular junction (in diseases such as myasthenia gravis) which block the nervous system's ability to activate motor units and effect correct range and strength of movements.

Causes:

- Brain tumor

- Cerebral palsy

- Guillain–Barré syndrome

- Hypothermia

- Lyme disease

- Stroke

- Intracranial hypertension (formerly known as pseudotumor cerebri)

- Tay-Sachs, and late onset Tay-Sachs (LOTS), disease

Basal ganglia disease is a group of physical s that occur when the group of nuclei in the brain known as the basal ganglia fail to properly suppress unwanted movements or to properly prime upper motor neuron circuits to initiate motor function. Research indicates that increased output of the basal ganglia inhibits thalamocortical projection neurons. Proper activation or deactivation of these neurons is an integral component for proper movement. If something causes too much basal ganglia output, then the thalamocortical projection neurons become too inhibited and one cannot initiate voluntary movement. These disorders are known as hypokinetic disorders. However, a disorder leading to abnormally low output of the basal ganglia leads to relatively no inhibition of the thalamocortical projection neurons. This situation leads to an inability to suppress unwanted movements. These disorders are known as hyperkinetic disorders. Currently, reasons for abnormal increases or decreases of basal ganglia output are poorly understood. One possible factor could be the natural accumulation of iron in the basal ganglia, causing neurodegeneration due to its involvement in toxic free-radical reactions. Though motor disorders are the most common associated with the basal ganglia, recent research shows that basal ganglia disorders can lead to other dysfunctions such as obsessive compulsive disorder (OCD) and Tourette syndrome.

Though it is often most associated with Parkinson's disease, hypokinesia can be present in a wide variety of other conditions.

DVD/CAS is a motor disorder, which means that the problem is located in the brain and its signals, and not in the mouth. In most cases, the cause is unknown. Possible causes include genetic syndromes and disorders.

Recent research has focused on the significance of the FOXP2 gene in both species and individual development.

Research regarding the KE family, where half the members of the extended family, over three generations, exhibited heritable developmental verbal dyspraxia, were found to have a defective copy of the FOXP2 gene. and further studies suggest that the FOXP2 gene as well as other genetic issues could explain DVD/CAS. including 16p11.2 microdeletion syndrome.

Birth/prenatal injuries, as well as stroke, can also be causes of DVD/CAS. Furthermore, DVD/CAS can occur as a secondary characteristic to a variety of other conditions. These include autism, some forms of epilepsy, fragile X syndrome, galactosemia, and chromosome translocations involving duplications or deletions.

Diseases that feature one or more hyperkinetic movements as prominent symptoms include:

There is physiological intracranial calcification in about 0,3-1,5% of individuals. Fahr's disease is a rare, genetically dominant, inherited neurological disorder characterized by abnormal deposits of calcium, primarily in the basal ganglia.

Developmental coordination disorder is a lifelong neurological condition that is more common in males than in females, with a ratio of approximately four males to every female. The exact proportion of people with the disorder is unknown since the disorder can be difficult to detect due to a lack of specific laboratory tests, thus making diagnosis of the condition one of elimination of all other possible causes/diseases. Approximately 5–6% of children are affected by this condition.

Stroke-associated AOS is the most common form of acquired AOS, making up about 60% of all reported acquired AOS cases. This is one of the several possible disorders that can result from a stroke, but only about 11% of stroke cases involve this disorder. Brain damage to the neural connections, and especially the neural synapses, during the stroke can lead to acquired AOS. Most cases of stroke-associated AOS are minor, but in the most severe cases, all linguistic motor function can be lost and must be relearned. Since most with this form of AOS are at least fifty years old, few fully recover to their previous level of ability to produce speech.

Other disorders and injuries of the brain that can lead to AOS include (traumatic) dementia, progressive neurological disorders, and traumatic brain injury.

Tic disorders is defined in the "Diagnostic and Statistical Manual of Mental Disorders" (DSM) based on type (motor or phonic) and duration of tics (sudden, rapid, nonrhythmic movements). Tic disorders are defined similarly by the World Health Organization (ICD-10 codes).

There are two types of Apraxia. Developmental (or Childhood Apraxia of speech) or acquired Apraxia. Childhood apraxia of speech (CAS) is a neurological childhood speech sound disorder that involves impaired precision and consistency of movements required for speech production without any neuromuscular deficits (ASHA, 2007a, Definitions of CAS section, para. 1). Both are the inability to plan volitional motor movements for speech production in the absence of muscular weakness. Apraxia is not a result of sensory problems, or physical issues with the articulatory structures themselves, simply the way the brain plans to move them.

Developmental coordination disorder is classified (by doctors) in the fifth revision of the "Diagnostic and Statistical Manual of Mental Disorders" (DSM-5) as a motor disorder, in the category of neurodevelopmental disorders.

Motor disorders are disorders of the nervous system that cause abnormal and involuntary movements. They can result from damage to the motor system.

Motor disorders are defined in the fifth edition of the "Diagnostic and Statistical Manual of Mental Disorders" (DSM-5) – published in 2013 to replace the fourth text revision (DSM-IV-TR) – as a new sub-category of neurodevelopmental disorders. The DSM-5 motor disorders include developmental coordination disorder, stereotypic movement disorder, and the tic disorders including Tourette syndrome.

Recent research has established the existence of primary progressive apraxia of speech caused by neuroanatomic motor atrophy. For a long time, this disorder was not distinguished from other motor speech disorders such as dysarthria and in particular primary progressive aphasia. Many studies have been done trying to identify areas in the brain in which this particular disorder occurs or at least to show that it occurs in different areas of the brain than other disorders. One study observed 37 patients with neurodegenerative speech disorders to determine whether or not it is distinguishable from other disorders, and if so where in the brain it can be found. Using speech and language, neurological, neuropsychological and neuroimaging testing, the researchers came to the conclusion that PAS does exist and that it correlates to superior lateral premotor and supplementary motor atrophy. However, because PAS is such a rare and recently discovered disorder, many studies do not have enough subjects to observe to make data entirely conclusive.

There are three significant features that differentiate DVD/CAS from other childhood speech sound disorders. These features are:

- "Inconsistent errors on consonants and vowels in repeated productions of syllables and words

- Lengthened coarticulatory transitions between sounds and syllables

- Inappropriate prosody, especially in the realization of lexical or phrasal stress"

Even though DVD/CAS is a "developmental" disorder, it will not simply disappear when children grow older. Children with this disorder do not follow typical patterns of language acquisition and will need treatment in order to make progress.

Parkinson's Disease is one of the most commonly known motor disorders. It is a disorder that slowly and progressively affects and alters movement, control and coordination of muscles, and balance. This disease is caused by cells being destroyed in the part of the brainstem called the substantia nigra. This is the part of the brain that controls coordination and movement ("Movement Disorders"). Symptoms of Parkinson’s disease include tremors, gait problems and spasms. One in five hundred people will have Parkinson’s disease. Being exposed to certain drugs or toxins that cause genetic mutation is the usual cause of Parkinson’s disease (Mandal). The treatments of Parkinson’s disease include medication and in some cases surgery. Medications commonly used as treatment are anticholinergics and dopamine enhancing drugs. Surgery is usually only considered when medication has been unsuccessful (“Movement Disorders”).

Dysarthrias are classified in multiple ways based on the presentation of symptoms. Specific dysarthrias include spastic (resulting from bilateral damage to the upper motor neuron), flaccid (resulting from bilateral or unilateral damage to the lower motor neuron), ataxic (resulting from damage to cerebellum), unilateral upper motor neuron (presenting milder symptoms than bilateral UMN damage), hyperkinetic and hypokinetic (resulting from damage to parts of the basal ganglia, such as in Huntington's disease or Parkinsonism), and the mixed dysarthrias (where symptoms of more than one type of dysarthria are present). The majority of dysarthric patients are diagnosed as having 'mixed' dysarthria, as neural damage resulting in dysarthria is rarely contained to one part of the nervous system — for example, multiple strokes, traumatic brain injury, and some kinds of degenerative illnesses (such as amyotrophic lateral sclerosis) usually damage many different sectors of the nervous system.

Ataxic dysarthria is an acquired neurological and sensorimotor speech deficit. It is a common diagnosis among the clinical spectrum of ataxic disorders. Since regulation of skilled movements is a primary function of the cerebellum, damage to the superior cerebellum and the superior cerebellar peduncle is believed to produce this form of dysarthria in ataxic patients. Growing evidence supports the likelihood of cerebellar involvement specifically affecting speech motor programming and execution pathways, producing the characteristic features associated with ataxic dysarthria. This link to speech motor control can explain the abnormalities in articulation and prosody, which are hallmarks of this disorder. Some of the most consistent abnormalities observed in patients with ataxia dysarthria are alterations of the normal timing pattern, with prolongation of certain segments and a tendency to equalize the duration of syllables when speaking. As the severity of the dysarthria increases, the patient may also lengthen more segments as well as increase the degree of lengthening of each individual segment.

Common clinical features of ataxic dysarthria include abnormalities in speech modulation, rate of speech, explosive or scanning speech, slurred speech, irregular stress patterns, and vocalic and consonantal misarticulations.

Ataxic dysarthria is associated with damage to the left cerebellar hemisphere in right-handed patients.

Dysarthria may affect a single system; however, it is more commonly reflected in multiple motor-speech systems. The etiology, degree of neuropathy, existence of co-morbidities, and the individual's response all play a role in the effect the disorder has on the individual's quality of life. Severity ranges from occasional articulation difficulties to verbal speech that is completely unintelligible.

Individuals with dysarthria may experience challenges in the following:

- Timing

- Vocal quality

- Pitch

- Volume

- Breath control

- Speed

- Strength

- Steadiness

- Range

- Tone

Examples of specific observations include a continuous breathy voice, irregular breakdown of articulation, monopitch, distorted vowels, word flow without pauses, and hypernasality.