Dyskinesia is a broadly encompassing term that is applied to many hyperkinetic involuntary movements including those taking the conventional forms of dystonia, chorea, athetosis, and tremor and the less well-defined ones that are produced by L-dopa therapy in Parkinson disease. When modified by the adjective tardive, it refers specifically to movements induced by the use of neuroleptic drugs, often but not always phenothiazines, that are delayed in onset from the initiation of drug therapy and persist after the drugs are withdrawn. These movements are distinguished from acute dystonic reactions that occur in the first few days of exposure to medications, are aborted by anticholinergic drugs, and do not persist. At one time, tardive dyskinesia was a common problem in psychiatric and general medical practice but it has been less prevalent with the newer classes of antipsychosis drugs. The problem is still easily recognized and familiar to physicians who treat psychiatric patients. The movements tend to lessen over a period of months or years and mild cases abate on their own or leave little residual effect; rarely have the symptoms worsened.
Tardive dyskinesias are intermittent or persistent and not subject to the will of the patient. The facial, lingual, eyelid, and bulbar muscles are most often involved but neck, shoulder, and spine muscles with arching of the back may be implicated in individual cases as noted below. There may be added blepharospasm and truncal, hand, or neck movements and akathisia of the legs, but these are not nearly so prominent as the orofacial and lingual dyskinesias. Longer exposure is more likely to cause the movements. If the drug is discontinued immediately after the movements appear, the problem may not persist. Oromandibular spasm and blepharospasm (Meige syndrome) and Huntington disease may cause difficulty in diagnosis.
In addition to the typical neuroleptic drugs, less familiar ones such as metoclopramide, pimozide, amoxapine, and clebopride, some of which are used for disorders other than psychosis, and newer agents such as risperidone may also be causative. Less often, the movements arise soon after cessation of one of these same drugs.
There are a number of other drug-induced tardive movement syndromes, mainly varieties of dystonias, some of which have been mentioned earlier, and akathisia (see further on). Often they begin focally in the neck and spread over time to the limbs. One highly characteristic pattern combines retrocollis, backward arching of the trunk, internal rotation of the arms, extension of the elbows, and flexion of the wrists simulating an opisthotonic posture. Other patients may have both orofacial and cervical dyskinesias. Many patients report that the dystonia abates during walking and other activities, quite unlike idiopathic torsion dystonia. These drug-induced dyskinesias are viewed as the result of changes in the concentration of dopamine receptors, five of which are currently known, as discussed earlier. Blockade and subsequent unmasking of the D2 receptor have been particularly linked to the development of the tardive syndromes.
Little has been found to be consistently effective. If the movements follow withdrawal of one of the offending drugs, reinstitution of the medication in small doses often reduces the dyskinesias but may have the undesired side effects of causing parkinsonism and drowsiness. For this reason most clinicians who are experienced in this field avoid using the known offending drugs if possible and choose one of the newer agents for the treatment of the underlying psychiatric condition. The newer “atypical” neuroleptic drugs have less of a propensity to cause tardive dyskinesia.
Dopamine and noradrenergic-depleting drugs such as reserpine and tetrabenazine have also been successful if used carefully but the more effective of the two, tetrabenazine, may be difficult to obtain. The dystonias also respond to anticholinergic drugs (trihexyphenidyl 2.5 mg once or twice daily, increased by small increments weekly up to 12.5 mg) if high enough doses can be tolerated.