Other abnormal movements

● Tremor

Tremor is a rhythmic, involuntary oscillatory movement of a body part, resulting from alternating or simultaneous muscle contractions. Its diagnostic specificity is enhanced by accompanying findings and varies depending on the type of tremor.

• Resting tremor: This occurs when the affected body part is relaxed. It may be accompanied by other features that support a picture of parkinsonism ➚ .

• Kinetic tremor: This occurs during voluntary movement. It may be accompanied by other features that support a picture of ataxia ➚ .

• Postural tremor: This occurs when a body part is maintained in a position against gravity. It may be encountered frequently in the setting of psychiatric disorders, often in the form of enhanced physiologic tremor associated with psychotropic medications (e.g., valproic acid, lithium, and several antidepressants), CNS stimulant use, anxiety disorders, and insomnia.

● Dyskinesia

Dyskinesia is a broad term encompassing various involuntary hyperkinetic movements and therefore has limited diagnostic specificity when considered in isolation. Dyskinesias may occur in association with other hyperkinetic movements, including chorea ➚ and tremor, and diagnostic significance depends on the phenomenology of the movement and the broader clinical context. Exposure to medications such as dopamine receptor-blocking agents or levodopa is an important diagnostic consideration.

Tardive dyskinesia is a persistent or recurrent hyperkinetic movement disorder associated with exposure to dopamine receptor-blocking agents, particularly antipsychotic medications. It most commonly manifests as repetitive oro-bucco-lingual movements, although other body regions may also be affected, and it may coexist with other tardive movement phenomena such as dystonia, akathisia, or stereotypies. Early recognition is important because tardive dyskinesia may persist despite withdrawal of the offending medication and, in some cases, may be permanent.

● Dystonia

Dystonia consists of sustained or intermittent muscle contractions that produce abnormal movements or postures, often with a twisting or patterned quality. When present in isolation, dystonia has a broad differential diagnosis, and diagnostic specificity is enhanced by the presence of other neurological or systemic findings, in addition to consideration of age at onset, distribution, temporal pattern, medication exposure, and other clinical factors.

● Myoclonus

Myoclonus consists of sudden, brief, involuntary jerks caused by either muscle contraction (positive myoclonus) or brief loss of muscle tone (negative myoclonus). Myoclonus has a broad differential diagnosis and may be classified as physiologic, essential, epileptic, or symptomatic (secondary). Symptomatic myoclonus is particularly important diagnostically, as it may occur across a wide range of neurologic and systemic disorders and is often accompanied by other clinical manifestations, such as cognitive abnormalities, ataxia ➚ , or other movement disorders ➚ . The accompanying clinical and electrophysiological features may therefore provide greater diagnostic specificity than the myoclonus itself. Toxic-metabolic and medication-related causes are particularly important considerations in the hospital setting.

● Athetosis and ballism/hemiballism

These were discussed as part of the choreiform spectrum of movements ➚ .

● Akathisia

Akathisia is characterized by a subjective sense of inner restlessness accompanied by a compelling need to move, often manifested by repetitive movements such as pacing, shifting position, or repeated crossing and uncrossing of the legs. It is particularly important to recognize in psychiatric practice because it is commonly associated with dopamine receptor-blocking medications, especially antipsychotic agents, and may otherwise be mistaken for anxiety, agitation, or worsening psychiatric illness.

● Tics

Tics are sudden, rapid, recurrent, non-rhythmic movements or vocalizations. Their phenomenology, including the presence of premonitory urges, partial suppressibility, and waxing and waning over time, can help distinguish them from other repetitive or involuntary movements. They are characteristic of Tourette syndrome and other conditions collectively termed tic disorders, but may also occur in other neurologic and psychiatric contexts.

● Stereotypies

Stereotypies are repetitive, often patterned movements or vocalizations that are typically more prolonged, rhythmic, and less variable than tics. They are particularly common in neurodevelopmental disorders, especially autism spectrum disorder, although they can also occur in other developmental, neurological, and psychiatric contexts.

● Mannerisms

Mannerisms are distinctive, repetitive, or exaggerated patterns of movement, gesture, or behaviour that are typically recognizable as elaborations of otherwise normal actions. They are particularly associated with severe psychiatric disorders, including schizophrenia-spectrum disorders, but can also occur in other psychiatric, neurologic, and developmental conditions; their diagnostic significance therefore depends largely on the broader clinical context.

● Functional movement disorder

Functional movement disorder (FMD) refers to abnormal movements arising in the context of functional neurologic disorder (FND), and may manifest as tremor, dystonia, myoclonus, parkinsonism ➚ , chorea ➚ , ataxia ➚ , gait disturbance, or other movement phenotypes. Diagnosis is based on positive clinical features demonstrating incongruence with recognized neurologic patterns, rather than simply on the presence of psychiatric symptoms or psychological stressors. It is worth noting that FMD may coexist with other neurologic disorders, and a comorbid psychiatric diagnosis is neither necessary nor sufficient for the diagnosis.