Tardive Dyskinesia & Parkinson's Disease
Both tardive dyskinesia and Parkinson's disease are classified as movement disorders. The causes of both conditions are related to dopamine, a neurotransmitter that carries signals from the brain to various parts of the body, regulating bodily functions. Both tardive dyskinesia and Parkinson's disease may be congenital (although this is exceedingly rare in the case of tardive dyskinesia), or the result of side-effects from a medication.
In many ways, tardive dyskinesia and similar (but unrelated) movement disorders are the opposite of Parkinson's disease. Tardive dyskinesia patients have great difficulty staying still, whereas those with Parkinson's disease have a great deal of difficulty moving at all.
Parkinson's disease (named for Dr. James Parkinson, who first described the disease in an article entitled "An Essay On Shaking Palsy" in the early 19th century) is characterized by the following primary symptoms:
- Muscular rigidity
- Tremors and shaking
- Impaired balance and coordination
- Loss of movement ability
Secondary symptoms of Parkinson's disease may include:
- Impaired Speech
- Difficulty swallowing
- Stooped posture
In the past, Parkinson's disease was most often attributed to genetic causes, but researchers are discovering and still debating that the causes could be mulitfactorial, including both genetic and environmental triggers. Toxicity from aluminum (an example of an environmental trigger), dopamine-inhibiting drugs and head injuries have been implicated as well.
Patients with tardive dyskinesia on the other hand display the following symptoms:
- Facial tics, including lip smacking and pursing, grimacing and rapid eye blinking
- Tongue-thrusting and "vacuous" cud-chewing motions of the jaw
- Fluttering fingers (as if playing an invisible piano or typing in the air)
- Languorous arm movements
- Restless leg, toe tapping
In some cases, the torso and hips as well as general movement can be affected. In a publication by the American Psychiatric Association, movements associated with tardive dyskinesia tend to be slower and more fluid and the tremors and jerky spasms associated with Parkinson's disease are not present.
It should also be noted that unlike Parkinson's disease, symptoms of tardive dyskinesia can actually disappear during sleep or when a patient is at rest, and can reappear when the patient is agitated or otherwise under stress.
Generally, the diagnostic process for tardive dyskinesia and Parkinson's disease is similar. Both require a thorough physical and neurological examination as well as a complete review of medical history. In both cases, it may be necessary for a physician to meet with the patient and make detailed observations over a period of time in order to determine the exact nature of the disorder. In most cases, the diagnosis is obtained through "differential" means, by a process of elimination.
Drugs used to treat mental illness work by blocking the receptors that receive signals from the brain. The signals are transmitted by the neurochemical dopamine, which is why these drugs are called "dopamine antagonists." In both tardive dyskinesia and Parkinson's disease, insufficient amounts of this chemical are produced, or the chemical and the receptors are not functioning as they should. This is why some patients on antipsychotic medications can sometimes develop symptoms of Parkinson's disease, although this is not necessarily the disease itself (symptoms without the disease are called "Parkinsonism"). However, true Parkinson's disease is most often genetic.
There have been extremely rare cases in which tardive dyskinesia has been known to appear in a patient for no known cause. In virtually all other cases however, the culprit is a dopamine antagonist.
Because both disorders are related to dopamine production and transmission, tardive dyskinesia and Parkinson's disease can be managed with many of the same treatments, though strictly speaking, neither are curable (tardive dyskinesia has been known to go into remission in many patients however, particularly if they have been on the drug for only a short time). Both may be treated and managed with a combination of levodopa and dopamine agonists (medications that facilitate the function of dopamine).