What Is Focal Dystonia?

Dystonia is a movement disorder that causes the body's muscles to involuntarily spasm, stiffen, or change position—usually for a few minutes at a time. Focal dystonia affects only one or a few areas of the body. Dystonia can interfere with movement, and the lack of motor control may sometimes cause emotional distress.

Often, focal dystonia is caused by an underlying neurological problem, and several conditions can lead to focal dystonia. This movement disorder can be managed with medication or other interventions, and the prognosis varies according to the cause.

This article describes the types, symptoms, causes, diagnosis, and treatment of focal dystonia, as well as an overview of what you should expect If you have this condition and how to cope.

Types of Focal Dystonia 

The different types of focal dystonia can be described with reference to the affected area of the body, the cause, or the situation in which they occur.

Some types of focal dystonia based on the body area affected are:

• Blepharospasm: The eyelids close involuntarily.
  
• Cervical dystonia: Neck muscle spasms cause your head to turn to one side.
• Laryngeal dystonia: A spasm of the throat can cause impaired speech or swallowing.
• Oromandibular dystonia: Involuntary movements of the mouth or tongue are among the types of focal dystonia.
• Hand dystonia: For some people, dystonia may only affect the hand on one side of the body.

Dystonias may also be grouped by causes or situations:

• Idiopathic dystonia/primary dystonia: Sometimes focal dystonia can occur without an identifiable cause (idiopathic).
• Medication-induced dystonia: Dystonia may occur as a side effect of certain medications.
• Intention dystonia: This type of dystonia occurs only during certain actions.

There can be an overlap between different types of focal dystonia. For example, it’s possible to have idiopathic hand dystonia.

Focal Dystonia Symptoms 

Focal dystonia can occur intermittently, with recurrent episodes of stiffening or movement of the affected part of the body. It can occur multiple times per day, or it may occur infrequently—such as once a week, or even less often. The involuntary movement can have a duration of minutes or longer.

When someone has focal dystonia, it can look like they are intentionally moving their body normally (even though it is not on purpose), or it might be obvious that they are twisting or turning part of their body in a way that doesn’t have a purpose or may look comfortable.

Some people might make an effort to conceal focal dystonia by hiding the involuntary movement (such as putting their hand in their pocket).

The symptoms of focal dystonia depend on which part of the body is affected. For example, the hand may bend involuntarily and remain in that position for several minutes at a time. Laryngeal dystonia may cause difficulty in speaking, and it may affect breathing.

Common symptoms of focal dystonia can include:

• Repetitive mouth movements
• Leg or foot flexion (movement towards the body) or extension (movement away from the body)
• Grimacing of the face
• Difficulty using the hand, possibly only during certain actions
• Sudden movement of one or more fingers

Dystonia may occur along with other movement impairments or disorders, such as hemiparesis (weakness of one side of the body), dyskinesia (involuntary muscle movements), tremors, or bradykinesia (slow movements). 

Causes 

Dystonia occurs when there is recurrent, purposeless motor stimulation of part of the body. This can occur due to disruption of the pathways in the brain that cause movement or inconsistency of the neurotransmitters (chemical messengers for nerve cells) that trigger movement. It can occur due to a genetic condition, medical condition, or without a known underlying cause.

Damage or dysregulation of the basal ganglia, a brain region involved in mediating tone and muscle movement, can cause focal dystonia. This area of the brain is affected by Parkinson's disease.

Medical conditions that can cause dystonia include:

• Parkinson's disease: This is a neurodegenerative disorder that can cause tremors, slow movements, and abnormal movements, including focal dystonia.
• Parkinsonism: Symptoms similar to those of Parkinson's disease can be caused by medications, stroke, head trauma, or other types of brain damage affecting neurotransmitters of the basal ganglia.
• Neuroleptic medications: Prescriptions used to treat Parkinson's disease, certain mental health conditions, and some gastrointestinal conditions may cause focal dystonia.
• Stroke: A stroke (blockage of blood flow or bleeding in the brain) can cause damage to any region of the brain, including the basal ganglia or regions that are part of the movement pathway, potentially causing focal dystonia
• Multiple sclerosis (MS): This inflammatory disorder causes a deficiency of myelin, which is the protective coating of the nerves. This condition affects the brain, spinal cord, and optic nerves (nerves carrying messages from the eye's retina to the brain). It can cause focal dystonia when it affects specific regions in the basal ganglia pathway or the motor regions of the spinal cord. 
• Head trauma: An injury affecting the brain may cause symptoms corresponding to the brain's damaged regions, which may result in dystonia.
• Cerebral palsy: This disorder is present from birth and may cause physical weakness, uncontrolled postures, cognitive effects, and movement disorders such as focal dystonia.
• Spinal cord disease: Disease or damage to the spinal cord can cause muscle weakness and changes in muscle posture, including focal dystonia.
• Genetic conditions: Some gene mutations have been identified in association with hereditary focal dystonia.
• Encephalitis or meningitis: Infections or inflammatory disorders that affect the brain (encephalitis) or the meningeal tissue surrounding the brain (meningitis) can cause serious symptoms such as seizures. Dystonia may be among the symptoms. Usually, the symptoms resolve as the infection or inflammation resolves, but if areas of the brain become damaged during the acute phase, then focal dystonia may persist.
• Wilson's disease: This metabolic condition can cause brain damage and movement disorders, including focal dystonia.

Diagnosis 

Focal dystonia is a clinical diagnosis recognized based on symptoms and physical examination. You may have one or more episodes of dystonia during your medical evaluation. If your movement symptoms do not occur frequently, you might consider taking a photo or a video that you can share when you go in for a medical visit.

During your evaluation, you can expect an examination of your muscle strength, tone, reflexes, and sensation. Often these other signs can help in determining the cause of your dystonia. 

Sometimes diagnostic imaging tests are part of the assessment of focal dystonia.

This may include:

• Imaging tests of the brain or spinal cord can help identify regions that may show signs of MS or a stroke.
• In some situations, nerve conduction studies (NCV) or electromyography (EMG) can help in the diagnosis.
• Genetic testing may be helpful if there is concern about a hereditary cause of dystonia.

A measure of the severity of dystonia may be defined by using the Unified Dystonia Rating Scale, which can help assess changes in focal dystonia. This can be useful in evaluating whether your treatment is helping or whether your dystonia is getting worse.

Treatment 

There are several treatment options for dystonia. Sometimes a combination of treatments is necessary to treat ongoing dystonia and prevent worsening dystonia. The treatment is directed toward the cause and the symptoms.

Treatments can include:

• Medications that are used to treat movement disorders, such as Parkinson’s disease
• Disease-modifying therapy for MS
• Adjusting or stopping a medication that is causing dystonia
• Physical therapy or occupational therapy to facilitate movement and muscle control after a stroke
• Botox (onabotulinumtoxinA) injection
• Surgical nerve transection (cutting the nerve to prevent movement)
• Brain surgery, which may include deep brain stimulation (implantation of an electrical device), potentially in a specific region of the brain, such as the thalamus

You might need to continue some of these treatments for months or years, such as physical therapy or medication. Surgical procedures for treating focal dystonia aim to be curative and are not intended to be repeated.

Prognosis 

The prognosis of focal dystonia varies, depending on the cause and severity. In general, new-onset dystonia treated shortly after the symptoms start is expected to have a better prognosis than dystonia that has been going on for years or longer.

Dystonia can often be effectively treated with long-term medication or surgery. However, some types of dystonia can be permanent and might not respond well to medication. For example, focal dystonia associated with congenital conditions, such as cerebral palsy, might not respond well to treatment.

Coping 

Living with dystonia can be physically limiting, as well as stressful. You may notice a pattern of involuntary movements, or they may occur without predictability. 

It can help to discuss the physical, emotional, and psychological impact that dystonia is having on your life with your healthcare providers. While it may be obvious that you should get treatment for the physical symptoms, it can also be beneficial for you to get professional guidance regarding the emotional and psychological effects. 

You may need to seek accommodations at work if your focal dystonia is preventing you from doing certain tasks.

Summary 

Focal dystonia is a type of movement disorder that causes involuntary muscle stiffening of one or a few parts of the body. This can occur intermittently, and it can be frequent or infrequent, depending on the underlying cause and situation.

Dystonia is typically caused by abnormal brain, spinal cord, or neurotransmitter function. Sometimes focal dystonia can be treated quickly and permanently, but in some situations, it requires long-term medication and other therapy.

Dystonia can be distressing, both physically and emotionally, and it’s important for you to seek support so that you can maintain your best physical function and quality of life as you manage your dystonia and the underlying cause.