Paroxysmal dyskinesias (PD) are episodic movement disorders in which abnormal movements are present only during attacks. The term paroxysmal indicates that symptoms are noticeable only at certain times. The term dyskinesia broadly refers to movements of the body that are involuntary. Between attacks most people are generally neurologically normal, and there is no loss of consciousness during the attacks.
Identifying the types of movements associated with PD is complicated. These movements may be dystonic, choreic, ballistic, or a combination. An individual may show one specific type of movement or a combination of movements.
Dystonic movements are typically patterned and repetitive, causing twisting movements and abnormal postures. Dystonia occurs when opposing muscles are contracting simultaneously. The activation of these muscles may "overflow" to other muscle groups unintentionally.
Ballistic movements are more severe limb movements that involve portions of the limb such as the shoulder and elbow, and hip and knee.
Choreic movements may be described as brief, rapid, involuntary movements that serve no purpose. When mild, choreic movements may resemble fidgeting.
Athetoid movements are slower and more continuous than chorea with a writhing quality. They especially involve the hands and may also affect the torso and other parts of the body.
When chorea and athetosis occur simultaneously, the term choreoathetosis has been used. Choreoathetosis may coexist with dystonia or occur independently.
Terms used to describe paroxysmal dystonia include: paroxysmal dyskinesias. Forms of paroxysmal dyskinesias may be referred to as paroxysmal kinesigenic dyskinesia, DYT10 dystonia; paroxysmal nonkinesigenic dyskinesia, paroxysmal choreoathetosis paroxysmal dystonic choreoathetosis, DYT8 dystonia; paroxysmal hypnogenic dyskinesia, paroxysmal exertion-induced dyskinesia
Note: Paroxysmal dyskinesias are sometimes classified under the dystonia umbrella, and sometimes considered a separate category of movement disorders. Paroxysmal hypnogenic dyskinesias may be classified as a form of epilepsy, not dystonia.
History and (ideally) video documentation of the attacks are important tools toward diagnosing PD. The work-up for diagnosing paroxysmal dyskinesias may also include an electroencephalogram (a test to measure brain waves), brain imaging (such as MRI or CT scan), blood chemistries, and calcium tests.
The paroxysmal dyskinesias are currently classified into four types:
- Paroxysmal kinesigenic (action-induced) dyskinesia (PKD)
- Paroxysmal non kinesigenic dyskinesia (PNKD)
- Paroxysmal exertion-induced dyskinesia (PED)
- Paroxysmal hypnogenic (nocturnal) dyskinesia (PHD)
[Note: Previous classifications included "paroxysmal choreoathetosis" and/or "paroxysmal dystonic choreoathetosis." Due to the variety of dyskinesias observed in PD, "paroxysmal dyskinesia" is a commonly used term.]
Paroxysmal Kinesigenic Dyskinesia (PKD) may be inherited, meaning that it is passed genetically from a parent or ancestor. Inherited PKD is an autosomal dominant disorder. (The term "autosomal dominant" indicates that only one parent need have the PKD gene in order for a child to inherit the disorder.) The age of onset in inherited cases of PKD is from five to fifteen years. PKD may also occur sporadically, meaning that symptoms manifest without a family history. The age of onset in sporadic cases is variable. In both cases the attacks, which may occur up to 100 times per day, are often precipitated by a startle, a sudden movement, a particular movement, or other factors. The attacks are usually short, lasting seconds or minutes. The symptoms may be preceded by an unusual sensation in the limbs and may be limited to one side of the body or a single limb. Most people with PKD have dystonia, and some have a combination of chorea and dystonia or ballism.
Paroxysmal Nonkinesigenic Dyskinesia (PNKD) is also inherited in an autosomal dominant fashion. The age of onset is usually between early childhood and early adulthood. The frequency of attacks is less than that of PKD, averaging between three per day to two per year. Fatigue, alcohol, caffeine, excitement, and other factors may trigger symptoms. The attacks generally last between a few seconds and four hours or longer. The attacks may begin in one limb and spread throughout the body, including the face. A person affected by PNKD may not be able to communicate during an attack but remains conscious and continues to breathe normally.
Paroxysmal Exertion-induced Dyskinesia (PED) . Both inherited and sporadic cases of PED have been reported. The attacks are triggered by prolonged exercise and may last between five to thirty minutes. The attacks may occur once a day or twice a month.
Paroxysmal Hypnogenic Dyskinesia (PHD) is characterized by attacks of dystonia, chorea, or ballism during non-REM sleep. These attacks may occur between five times a night to five times a year and usually last between thirty to forty-five seconds. The attacks may also sometimes occur during the day. PHD is probably a broad condition consisting of a several different types of episodes and symptoms.
A miscellaneous episodic dystonic condition is benign paroxysmal torticollis of infancy, which typically begins in the few months after birth. These attacks may occur once every two or three weeks and last from hours to days. Typically, the head and/or trunk tilt to one or the other side. These symptoms are often treated with specific physical therapy and disappear when the child is between one and five years old.
As is the case with most dystonias, paroxysmal dyskinesias are generally attributed to dysfunction in the area of the brain called the basal ganglia. However, much has yet to be learned about how and why PD occurs. Some regard PKD as a form of epilepsy involving specific parts of the brain (i.e., the basal ganglia and thalamus). There is a growing resource of evidence that suggests that PKD may in fact belong to a group of disorders similar to the inherited episodic ataxias, which are known to be associated with disorders of ion-channels. (Ion channel genes are responsible for the proteins that regulate the passage of salt atoms into and out of cells.)
Although the exact origin may not be known, most cases of PD are inherited or sporadic. A gene for PNKD has been located on chromosome 2q, and a gene for PKD on chromosome 16.
Cases of PD that are not considered inherited or sporadic and are associated with specific factors and conditions are classified as "secondary."
Secondary causes of PKD include multiple sclerosis, cerebral palsy, metabolic disorders, physical trauma, cerebrovascular disease, and miscellaneous conditions including supranuclear palsy and AIDS. Most conditions associated with PKD may also be associated with PNKD. A few cases of secondary PED and PHD have been reported.
Paroxysmal dyskinesias have also been associated with encephalitis and injury to the brain due to stroke and tumors. Drugs such as cocaine and dopamine blocking agents may also induce dyskinesias.
In extremely rare cases, paroxysmal dyskinesias may be a manifestation of a psychiatric disorder. Only a qualified movement disorder and/or conversion disorder expert (preferably a team of multiple specialists that includes both) should make such a diagnosis. Unfortunately, authentic cases of PD have often been inappropriately dismissed as "psychogenic." An inaccurate psychiatric diagnosis not only causes unnecessary suffering to the person affected by PD, but it may also preclude appropriate treatment options.
There is no cure for dystonia or PD at this time, but treatments are available. These treatments aim to reduce muscle spasms, pain, and disturbed posture and function.
The current poor understanding of the pathophysiology and biochemistry of PD often makes establishing a satisfactory treatment plan difficult. Treatment needs to be tailored to the individual, and it may be necessary to try several options before symptoms are diminished or alleviated. Patience on the part of both physician and patient is important.
People with PKD generally respond well to anticonvulsant agents such as phenytoin, primidone, valporate, carbamazepine, phenobarbital, and diazepam. Other drugs that may be helpful include anticholinergics, levodopa, flunarizine, and tetrabenazine. Haloperidol has given inconsistent results.
PNKD may respond to clonazepam, haloperidol, alternate day oxazepam, and anticholinergics. Anticonvulsants are ineffective in most cases. Trying to avoid triggering factors such as alcohol and caffeine is important.
There are a few cases of PED that improve with levodopa and acetazolamide, but drug treatment is ineffective for the most part. Avoidance of prolonged exercise may reduce frequency of attacks.
People who experience short attacks of PHD may respond to anticonvulsant drugs, including carbamazepine and phenytoin. Those who experience longer attacks may respond to haloperidol or acetazolamide.
Secondary PD associated with multiple sclerosis responds well to anticonvulsants. Acetazolamide may be a helpful alternative or adjunct agent to anticonvulsants. PD due to head injury may improve with anticonvulsant medications or a combination of anticonvulsants and trihexyphenidyl. Underlying conditions need to be addressed in other cases of secondary PD.
The intermittent and transient nature of paroxysmal dyskinesia generally precludes the use of therapies such as botulinum toxin injections and surgery.