Dyskinesia is a movement disorder which consists of adverse effects including diminished voluntary movements and the presence of involuntary movements, similar to tics or chorea. Dyskinesia can be anything from a slight tremor of the hands to uncontrollable movement of, most commonly, the upper body but can also be seen in the lower extremities. Discoordination can also occur internally especially with the respiratory muscles and it often goes unrecognized. Dyskinesia is a symptom of several medical disorders which are distinguished by their underlying cause.
Levodopa-induced dyskinesia (LID) is evident in patients with Parkinson's disease who have been on levodopa (L-DOPA) for prolonged periods of time. LID commonly first appears in the foot, on the most affected side of the body. There are three main types that can be classified on the basis of their course and clinical presentation following an oral dose of L-DOPA:
Off-period dystonia - correlated to the akinesia that occurs before the full effect of L-DOPA sets in, when the plasma levels of L-DOPA are low. It generally occurs as painful spasms in the foot. They[who?] will respond to L-DOPA therapy.
Diphasic dyskinesia - occurs when plasma levodopa levels are rising or falling. This form tends to predominate in lower limbs, and is usually dystonic or ballistic.[clarify] It does not respond to L-DOPA reduction.
Peak-dose dyskinesia - the most common form of LID; it correlates with the plateau L-DOPA plasma level. This type usually involves the upper limbs more (but could also affect the head, trunk and respiratory muscles), is choreic (of chorea), and less disabling. They[who?] will respond to L-DOPA reduction but may be accompanied by deterioration of parkinsonism. Peak-dose Levodopa-induced dyskinesia has recently been suggested to be associated with cortical dysregulation of dopamine signaling.
Late-onset dyskinesia, also known as tardive dyskinesia, occurs after treatment with an antipsychotic drug such as haloperidol (Haldol) or amoxapine (Asendin). The symptoms include tremors and writhing movements of the body and limbs, and abnormal movements in the face, mouth, and tongue – including involuntary lip smacking, repetitive pouting of the lips, and tongue protrusions.