Tardive dyskinesia: a glossary of terms

Tardive dyskinesia, or TD, is a disorder that causes involuntary movements. These involuntary movements can include grimacing, blinking, chewing motions, and other movements in the face and mouth. They can also affect other areas of the body.

TD most often affects people who take neuroleptic medications, which are often prescribed for schizophrenia. Schizophrenia is a psychiatric condition that disrupts a person’s ability to interpret reality. People with schizophrenia may experience hallucinations, delusions, depression-like symptoms, and problems with cognition and memory.

Neuroleptic medications are also called antipsychotic medications. In addition to schizophrenia, neuroleptic medications are prescribed for the treatment of manic episodes, depression, anxiety, and other psychiatric disorders. The exact reason why some people who take neuroleptic medications develop TD is unknown.

If you or a loved one has TD or has symptoms of TD, it can help to learn more about the condition. While there is plenty of information to be found, the terminology can sometimes be confusing, especially if you are just starting to research the condition.

Below are some key terms you may come across, with brief explanations.

• Tardive means “delayed.”
• Dyskinesia means “abnormal movement."
• Extrapyramidal side effects (EPS) are also called “drug induced movement disorders.” TD is one example, though there are numerous others. Extrapyramidal refers to the part of the nervous system that controls the initiation of movement as well as posture and muscle tone.
• First-line neuroleptics refer to older neuroleptic medications, generally those that became available between the 1950s and 1980s. Some of these medications are still prescribed today.
• Second-line neuroleptics refer to neuroleptic medications that became available beginning in the 1980s. The vast majority of neuroleptic medications used today are second-line neuroleptics. Second-line neuroleptics are preferred because they are generally associated with fewer side effects.
• Atypical neuroleptic drugs or “atypical antipsychotic drugs” refer to second-line neuroleptic drugs. By contrast, first-line neuroleptics are sometimes called “traditional antipsychotic drugs” or “traditional neuroleptic drugs.”
• Dopamine is a neurotransmitter, a chemical messenger that facilitates communications between nerve cells in the brain. Some research suggests that abnormal dopamine function contributes to schizophrenia. Some neuroleptic drugs work by blocking dopamine receptors, others work by blocking dopamine and serotonin, another neurotransmitter.
• VMAT2 inhibitors or vesicular monoamine transporter 2 inhibitors are medications that are used to control the symptoms of TD. These drugs work by regulating chemical signaling in the brain. They are used to treat other involuntary movement disorders as well. There are currently two VMAT2 inhibitors approved by the FDA for the treatment of TD.
• Deep brain stimulation is another therapeutic option for TD. It involves electrodes that are implanted in specific locations in the brain. These electrodes help regulate signaling in the brain. Deep brain stimulation is also used as a treatment for other neurological disorders, including epilepsy and Parkinson’s disease.
• Tardive dystonia is a severe form of TD. People who have tardive dystonia experience involuntary movements in the trunk, neck and shoulders.

If you or a loved one has TD or has symptoms of TD, it is important to seek treatment—and seek treatment as soon as possible. In many cases, symptoms can become permanent, and early diagnosis and treatment are essential.