Movement disorders are neurological diseases characterized by an abnormality of motor control because of diminished voluntary movements or increased involuntary movements. Movement disorders are generally classified as hypokinetic or akinetic-rigid syndromes or hyperkinetic disorders. Hypokinetic disorders disorders are diseases where patients have slowness of voluntary movement (bradykinesia) and muscle rigidity (stiffness) or, in general, diminished and slowed automatic movements (such as eye blinking or arm swing when walking). The most common of these disorders is Parkinson’s disease (PD) but other degenerative disorders include: progressive supranuclear palsy (PSP), multiple system atrophy (MSA) and corticobasal ganglionic degeneration. Hypokinetic disorders can also occur because of stroke or medications. Hyperkinetic disorders include diseases where there is too much movement and best known of these are Huntington’s disease (HD), Tourette’s syndrome (TS), essential tremor (ET), and dystonia.
Parkinson’s disease affects approximately 1.5 million people in the United States. It is a progressive neurological disorder characterized by the presence of tremor at rest, muscle stiffness or rigidity, slowness of movement or bradykinesia, and gait and balance problems such as shuffling, freezing or falling. This disease is associated with a loss of the neurochemical dopamine in the brain. The dopamine producing cells, particularly in a region of the brainstem called substantia nigra, progressively die off for reasons that remain unknown. This progressive loss of cells leads to increasing disability over time. Currently, there are many treatments available that primarily control the symptoms of this disorder, most of which replenish the missing dopamine. They include: the dopamine precursor levodopa, dopamine agonists (pramipexole, ropinirole, apomorphine), Catechol-O-methyltransferase (COMT) inhibitors (entacapone, tolcapone), Monoamine oxidase inhibitors (selegiline and rasagiline) and amantadine. The surgical treatment, deep brain stimulation, has been developed for the treatment of more advanced patients with intractable tremor, dyskinesia and severe off times. Research to uncover the cause of disease has included the search for genes (there are currently over 20 recognized to relate to Parkinson’s disease) and the study of environmental exposures such as pesticides. Many questions still exist.
Huntington’s disease is a hereditary progressive neurological disorder that affects approximately 100,000 people in this country. It is inherited in an autosomal dominant fashion, which means that each child of a person with this disease has a 50% chance of inheriting it. It is characterized by involuntary movements or chorea (Latin term for dance), gait abnormalities with falling, psychiatric symptoms such as depression, anxiety and even psychosis, and cognitive decline (dementia). It affects patients in the prime of life (average around age 35) and progresses to a severely debilitating state over 5-20 years. The gene for HD was discovered in 1993 and we are now able to predict if an at-risk person will develop the disease. At this time there are no treatments that can alter the progressive course of Huntington’s disease although several agents are under investigation. The discovery of the gene has lead to the development of animal models that may, in the near future, make the discovery of treatments a reality.
Essential tremor is probably the most common of movement disorders affecting about 5-10% of the population. It is inherited in an autosomal recessive manner in many cases and is characterized by tremors. Unlike Parkinson’s disease where the tremor occurs while sitting at rest, essential tremor is associated with postural and action tremors, which interfere with such activities as writing, eating and performing fine motor movements. It can occur at any age. It is sometimes very mild and not troublesome but it can be progressive and result in severe disability. Two genes have been associated with ET and further research may delineate a cause. Currently there are some medications that may be helpful in diminishing the tremor including propranolol, primidone, gabapentin, and topiramate but none are capable of stopping it. In the last 10 years, surgical therapy with deep brain stimulation has been shown to be very helpful.
Dystonia is a movement disorder characterized by involuntary muscle contraction leading to abnormal postures and twisting movements. The frequency of this disorder is similar to multiple sclerosis. Several types are known and they are classified according to age of onset, distribution of dystonia, and cause. The primary dystonias are diseases that are characterized with only dystonia as their clinical feature. They are classified as early onset or adult onset disease. The characteristic form of early onset form is called “primary childhood onset dystonia” otherwise known as Oppenheim’s dystonia or DYT1 dystonia. This disease begins frequently with dystonia in a limb and with onset under the age of 28. It characteristically progresses to involve other body parts and ultimately becomes generalized. It is a hereditary (autosomal dominant) disorder and the gene has been isolated. The adult onset dystonias are far more common and cervical distribution (otherwise known as spasmodic torticollis) is the most common type. The adult onset dystonias usually remain localized to specific areas such as neck, face or vocal cords. And they generally do not spread and are much less frequently hereditary. For cervical dystonia, typical age of onset is around 40 years and women are more affected than men. The cause of dystonia is unknown although genetic studies have shed some light on this. The primary treatment for the focal adult onset dystonias is Botulinum toxin. There are currently two types of toxins – Type A (3 different formulations) and Type B. Deep brain stimulation surgery similar to that utilized in Parkinson’s disease and essential tremor is very effective for those with generalized dystonia and for focal forms that no longer respond to the botulinum toxins.
Tourette’s syndrome is a common childhood onset hereditary neurological and behavioral disorder. It is characterized by the presence of motor or vocal tics but is also associated with several psychiatric disorders. The most common of these are attention deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD). The spectrum of Tourette’s syndrome is actually quite varied. Some patients can have a transient tic disorder that lasts less than a year and disappears while others can have the full-blown neurobehavioral disorder characterized by all of the features noted above and others as well. Some patients have chronic multiple motor tic disorder without vocal tics and the opposite is also true. The cause of this disease is unknown and the genetic basis of the disease also remains a mystery. There are several medical treatments for Tourette’s syndrome, including clonidine, dopamine antagonist agents and others, although they can be helpful in controlling tics and the behavioral disorders, they may be difficult to tolerate and only provide partial relief. Newer treatments are currently under investigation. This includes the use of deep brain stimulation. While some patients have a very mild form of Tourette’s syndrome, many of them may have it severe enough to interfere with their ability to participate in school and other important activities of childhood and adulthood.
These, and other movement disorders, are the focus of the Movement Disorders Program of Emory University. In the last 15 years, work in these disorders has been expanding and lead to the development of new treatments. For instance, Emory University physicians and scientists have been at the heart of the development of surgical therapies. Our goal is to provide comprehensive care for patients with these disorders. The key element for this goal is the employment of neurologists who have received subspecialty training in movement disorders above and beyond that of standard neurology residency.