An Underrecognized Phenomenon

A ntipsychotic medications were introduced in the 1950s and proved to be invaluable in the amelioration of schizophrenic symptoms. These agents gained widespread acceptance in the treatment of psychoneurologic disorders, including schizophrenia, Tourette’s syndrome, effective disorders, and dementia. Antipsychotics are also called neuroleptics because of their ability to induce a variety of neurologic side-effects. These include acute dystonia, parkinsonism, akathisia, and tardive dyskinesia. Of these sequelae, tardive dyskinesia is perhaps the most feared, due to its often dramatic and disabling presentation as well as its frequent irreversibility. The hyperkinetic movements in tardive dyskinesia most commonly consist of stereotypy or dystonia and usually affect the face, tongue, and neck.’ The limbs and trunk are less commonly involved. Chronic blockade of dopamine receptors by antipsychotics is thought to result in supersensitivity of the dopamine receptors in the nigrostriatal pathway that modulates voluntary movement. Involuntary dyskinesias thereby occur. The phenomenon typically requires at least 3 months of neuroleptic use and may occur up to 1 year after withdrawal of the medicine.2 Best estimates place the prevalence of tardive dyskinesia at 20 percent of patients using long-term neuroleptics.3 One family of neuroleptics is the phenothiazines. Included in this family of drugs are the antiemetics, such as promethazine (Phenergan; Wyeth) and prochlorperazine (Compazine; Smith Kline & French). Another antiemetic, metaclopramide (Reglan; Robins), is also used in the treatment of gastroesophageal reflux disease and diabetic gastroparesis. Long-term use of all of these agents has been associated with development of tardive dyskinesia.4’5 Treatment with levodopa (contained in Sinemet; Merck Sharp & Dohme), a dopamine precursor used in the treatment of parkinsonism, has been found to induce movement disorders in 30 to 80 percent of these patients.6 Though tardive dyskinesia generally confines itself to the head, neck, and limbs, some patients suffer from a variant referred to as respiratory dyskinesia. Respiratory dyskinesia is an irregular, tachypneic pattern of breathing due to involvement of the respiratory muscles by tardive dyskinesia. Very few primary care physicians or subspecialists recognize and understand respiratory dyskinesia. When reviewing tardive dyskinesia, textbooks and articles either fail to discuss this respiratory variant or dismiss it as rare. Unfortunately for those afflicted, respiratory dyskinesia is not rare. It may mimic other respiratory or cardiac disorders and is often overlooked or misdiagnosed. Consequently, potentially beneficial interventions are not initiated in these patients. In some patients, unnecessary and potentially hazardous investigations are undertaken. The case studies presented below exemplify neuroleptic-induced and levodopa-induced respiratory dyskinesia. A review of the literature pertaining to respiratory dyskinesia follows. Clues to the diagnosis, differentiation, and treatment of this disorder are then offered.