Movement disorders are neurological conditions that affect the speed, fluency, quality, and ease of movement. Abnormal fluency or speed of movement (dyskinesia) may involve excessive or involuntary movement (hyperkinesia) or slowed or absent voluntary movement (hypokinesia).
Movement disorders include the following conditions:
Common dystonias include spasmodic torticollis, which affects muscles of the head, face, and neck, and blepharospasm, which causes involuntary closing of the eyelids.
Tourette's syndrome is an inherited disorder characterized by multiple motor and vocal tics (repeated muscle contractions). Symptoms of Tourette's usually develop during childhood or early adolescence. Patients with the disorder often develop behavioral problems such as hyperactivity, inattention, impulsivity, obsessions, and compulsions. In most cases, symptoms vary in frequency and in severity.
Tics are involuntary muscle contractions that interrupt normal activities. They often are preceded by a strong sensation or urge that is temporarily relieved following the muscle contraction. Examples of common tics include the following:
Causes and Risk Factors
Movement disorders occur as a result of damage or disease in a region located at the base of the brain (basal ganglia). The basal ganglia is comprised of clusters of nerve cells (neurons) that send and receive electrical signals and are responsible for involuntary movement. Movement disorders can result from the following:
Signs and Symptoms
Symptoms of movement disorders often vary and fluctuate. The severity of symptoms may be affected by factors such as anxiety, fatigue, medication, and stress.
Some movement disorders cause hyperkinesia (i.e., excessive spontaneous movement or abnormal involuntary movement) and others cause hypokinesia (i.e., absent or reduced ability to perform purposeful movement).
Abnormal movements may be rhythmical (e.g., essential tremor) or irregular and may be rapid and jerky (e.g., tics) or slowed and sustained (e.g., Parkinson's disease, dystonia). In most cases, irregular movement cannot be consciously controlled or suppressed.
Diagnosis of movement disorders involves taking a family history and a history of symptoms, and performing a physical examination (including neurological examination) and various tests (e.g., blood tests, imaging tests).
Blood tests may include a complete blood count (CBC), a creatine kinase test, and a DNA analysis. In some cases, a cerebrospinal fluid (CSF) analysis also is performed.
Cerebrospinal fluid analysis involves performing a spinal tap, or lumbar puncture. In this procedure, about 2 tablespoons of cerebrospinal fluid is drawn into a needle inserted between two lumbar vertebrae and then examined under a microscope.
Imaging tests, including computed tomography (CT scan), magnetic resonance imaging (MRI scan), and positron emission tomography (PET scan), may be used to detect damage (e.g., shrinkage) in the basal ganglia, structural abnormalities, and stroke.
An electromyogram (EMG) and an electroencephalogram (EEG) also may be performed. These tests are used to monitor electrical activity within the body and can help detect nerve and muscle disorders. EMG involves placing electrodes on the skin (surface EMG) or into the muscle (intramuscular EMG) to record electrical activity of the muscle. In an EEG, electrodes are attached to the scalp and connected to a machine that records electrical impulses in the brain.
A muscle biopsy may also be performed to distinguish between nerve and muscle disorders. This procedure, which is performed under local anesthesia, involves making a small incision and removing a sample of muscle for microscopic evaluation. Following the procedure, patients may experience minor pain and bruising at the biopsy site for about 1 week.
Treatment for movement disorders depends on the underlying cause. In most cases, the goal of treatment is to relieve symptoms. Treatment may include medication, botulinum toxin injection therapy (BOTOX® therapy), and surgery.
Medications that may be used include the following:
Side effects of antiepileptics include dizziness, drowsiness, nausea, and vomiting. Antiseizure medications may cause a lack of coordination and balance (ataxia), dizziness, nausea, and fatigue. Benzodiazepines may cause blood clots (thrombosis), drowsiness, and fatigue. Side effects caused by beta-blockers include slowed heart rate (bradycardia), depression, light-headedness, and nausea. Dopamine agonists may cause nausea, headache, dizziness, and fatigue.
Parkinson's disease may be treated using a number of different medications.
Botulinum toxin injection therapy (BOTOX® therapy) is used to treat some types of movement disorders (e.g., spasmodic torticollis, blepharospasm, myoclonus, tremor). In this treatment, a potent neurotoxin (produced by the bacterium Clostridium botulinum) is injected into a muscle to inhibit the release of neurotransmitters that cause muscle contraction.
In some cases, treatment is repeated every 3 to 4 months. Patients may develop antibodies to the toxin over time, causing treatment to become ineffective. Side effects include temporary weakness in the group of muscles being treated and rarely, flu-like symptoms.
When medication is ineffective, severe movement disorders may require surgery. In deep brain stimulation (DBS), a surgically implanted, battery-operated medical device (neurostimulator) is used to deliver electrical stimulation to areas of the brain that control movement. The electrical charge blocks nerve signals that trigger abnormal movement.
In DBS, an electrode (lead) is inserted through a small incision in the skull and is implanted in the targeted area of the brain. An insulated wire (extension) is then passed under the skin in the head, neck, and shoulder, connecting the lead to the neurostimulator, which is surgically implanted in the chest or upper abdomen.
Side effects of deep brain stimulation include:
Ablative surgery locates, targets, and then destroys (ablates) the clearly defined area of the brain that produces chemical or electrical impulses that cause abnormal movements.
In this surgery, a heated probe or electrode is inserted into the targeted area. The patient remains awake during the procedure to determine if the problem has been eliminated. A local anesthetic is used to dull the outer part of the brain and skull. The brain is insensitive to pain, so the patient does not feel the actual procedure. In some cases, it may be difficult to estimate how much tissue to destroy and the amount of heat to use.
This type of surgery involves either ablation in the part of the brain called the globus pallidus (called pallidotomy) or ablation of brain tissue in the thalamus (called thalamotomy). A related procedure, cryothalamotomy, uses a supercooled probe that is inserted into the thalamus to freeze and destroy areas that produce tremors.
Pallidotomy may be used to eliminate uncontrolled dyskinesia (e.g., jerky, involuntary movements) and thalamotomy may be performed to eliminate tremor. These procedures are successful in approximately 75% of cases.