Focal dystonia

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Focal dystonia, also called focal task-specific dystonia, is a neurological condition that affects a muscle or group of muscles in a specific part of the body during specific activities, causing involuntary muscular contractions (spasms) and abnormal postures. There are many different types of focal dystonia, each affecting a different region of the body. For example, in focal hand dystonia, or writer's cramp, the fingers either curl into the palm or extend outward without control. In musicians, the condition is called musician's focal dystonia, or simply, musician's dystonia. In sports, it may be involved in what is commonly referred to as the yips. The condition appears to be associated with over-training, and individualized treatment strategies may involve medications, retraining techniques, and procedures.

Contents

Signs and symptoms

People with dystonia experience tightness, cramping, fatigue, involuntary sustained or repetitive muscle contractions that can be painless or painful and resulting in abnormal posturing, twisting motions, and even tremors. [1] [2] Focal dystonia typically presents in adults, more commonly in women ranging from ages 30 through 40. [1] Major types of focal dystonia affect the limbs, face, mouth, neck, and larynx. [3] These focal dystonias can be exclusive to specific tasks, like writing or playing an instrument. [4] Focal dystonia will typically have a subtle and slow onset before slowly worsening over years. [1] During the beginning stages, symptoms can be intermittent and without clear associations and provocation. [1] The progression of this disease can vary from person to person. [1] During the first couple years of onset, symptoms can partially or completely disappear for days to months, but return in other parts of the body. [1]

Causes

Current medical science does not precisely describe the causes of dystonia, however genetic and environmental factors may play a large role. [4] Misfiring of neurons in the sensorimotor cortex, a thin layer of neural tissue that covers the brain, is thought to cause contractions. This misfiring may result from impaired inhibitory mechanisms during muscle contraction. [5] When the brain tells a given muscle to contract, it simultaneously silences muscles that would oppose the intended movement. It appears that dystonia interferes with the brain's ability to inhibit those surrounding muscles, leading to loss of selectivity. [5]

The sensorimotor cortex is organized as discrete "maps" of the human body. Under normal conditions, each body part (such as individual fingers) occupies a distinct area on these cortical maps. In dystonia, these maps lose their distinct borders and overlap occurs. [6] Exploration of this initially involved over-training particular finger movements in non-human primates, which resulted in the development of focal hand dystonia. Examination of the primary somatosensory cortex in the trained animals showed grossly distorted representations of the maps pertaining to the fingers when compared to the untrained animals. [6] Additionally, these maps in the dystonic animals had lost the distinct borders that were noted in the untrained animals.

Imaging studies in humans with focal dystonia have confirmed this finding. [7] Also, synchronous afferent stimulation of peripheral muscles induces organizational changes in motor representations, characterized both by an increase in map size of stimulated muscles and a reduction in map separation, as assessed using transcranial magnetic stimulation. [8]

The cross-connectivity between areas that are normally segregated in the sensory cortex may prevent normal sensorimotor feedback and so contribute to the observed co-contraction of antagonist muscle groups, and inappropriately timed and sequenced movements that underlie the symptoms of focal dystonia. It is hypothesized that a deficit in inhibition caused by a genetically mediated loss of inhibitory interneurons may be the underlying cause of the deficits observed in dystonia. [5]

While usually painless, in some instances the sustained contraction and abnormal posturing in dystonia cause pain. Focal dystonia most typically affects people who rely on fine motor skills—musicians, writers, surgeons, etc. It is thought that the excessive motor training those skills require may contribute to the development of dystonia as their cortical maps become enlarged and begin to overlap. [9] Focal dystonia is generally "task-specific," meaning that it is only problematic during certain activities. [1]

Diagnosis

The diagnosis of focal dystonia is highly dependent on the history of the patient, as physical exam is typically normal, and ruling out other causes of movement disorder. [10] [11] The main types of are blepharospasm, oromandibular dystonia, spasmodic dysphonia, spasmodic torticollis, and limb dystonia, all affecting a different region of the body. [3] Labs and imaging may be ordered as workup to evaluate for other causes of dystonia. [12] A provider can rule in or out dopamine-responsive dystonia with a levodopa trial. [12]

Treatment

Treatment options would be based on the type of focal dystonia the patient has. [13] If possible, incorporating rest earlier to symptom onset has shown to have greater improvement in symptoms for writer's cramp. [2]

Physical therapy

Physical therapy is commonly used as an adjunct or main form of treatment for focal dystonia, however more studies for its benefit are needed. [14] Bass guitarist and instructor Scott Devine said that he wears a glove while playing bass guitar because of the condition. He finds that the glove stops the involuntary finger movements. He says it works for him but does not suggest that it may work for everyone with the condition. [15]

Medications

Anticholinergics such as Artane can be prescribed for off-label use, as some patients have had success. [16] Benzodiazepines, such as Clonazepam, can be used as a muscle relaxant. [13] Other oral medications have been studied for different types of focal dystonia, such as baclofen, tetrabenazine, amantadine, antipsychotics, and amphetamine [13]

Procedures

This condition is often treated with injections of botulinum neurotoxin type A (BoNT/A). BoNT/A reduces the symptoms of the disorder but it is not a cure for dystonia. Since the root of the problem is neurological, doctors have explored sensorimotor retraining activities to enable the brain to "rewire" itself and eliminate dystonic movements. The work of several doctors such as Nancy Byl and Joaquin Farias has shown that sensorimotor retraining activities and proprioceptive stimulation can induce neuroplasticity, making it possible for patients to recover substantial function that was lost to focal dystonia. [17] [18] [19] [20] [21] [22] For some dystonias, Deep brain stimulation may be considered where BoNT treatment fails. [13] If the dystonia is cause by an underlying nerve entrapment, surgical decompression has shown to have improvement in some cases. [2]

Prognosis

Recovery from focal dystonia has varying results, ranging from minimal improvement in function to complete recovery and ranging from weeks to years. [13]

Prevention

Though studies on prevention of focal dystonia is limited, it is believed for musician's dystonia that mindfulness of muscle use and proper rest can help prevent focal dystonia and injury. [2]

Performing arts medicine

Musician's dystonia

Musician's dystonia treatment studies have yielded varying results. [11] This condition can often be misdiagnosed as psychogenic, as this was previously thought to be its cause. [2] In this population, men are affected more than women from 20 to 60 years of age. [4] Evaluation of musician's dystonia should include history before and after symptom onset and observation of playing the instrument, as deficits can be subtle and considered minor to the general population. [2] Treatment modalities available, such as BoNT/A, leave many musicians unsatisfied due to muscle weakness and lack of improvement in muscle control. [11] In musicians, this is commonly associated with overuse or high volume of practicing. [4] Though musician's dystonia presents initially as task-specific, one study found that the dystonia can progress outside of playing their instrument. [2]

Treatments such as splinting and sensorimotor retraining for focal hand dystonia have shown to be beneficial with varying results. [2] It is important to consider the mental health and social aspect of this condition as a musician's self-identity and career can be affected considerably. [10] The approach to treating musician's dystonia requires an understanding and collaboration with the musician to obtain a complete history and tailor treatment and education effectively. [10] The most successful treatment for musician's dystonia has been a multidisciplinary approach, involving physicians, physical therapists, physiotherapists, psychologists, and music instructors, focusing on rehabilitation that can involve retraining the brain to play their instrument again and even learning to play other instruments. [11]

Noted patients

Related Research Articles

<span class="mw-page-title-main">Torticollis</span> Abnormal, asymmetrical head or neck position

Torticollis, also known as wry neck, is a painful, dystonic condition defined by an abnormal, asymmetrical head or neck position, which may be due to a variety of causes. The term torticollis is derived from Latin tortus 'twisted' and collum 'neck'.

<span class="mw-page-title-main">Myoclonus</span> Involuntary, irregular muscle twitch

Myoclonus is a brief, involuntary, irregular twitching of a muscle, a joint, or a group of muscles, different from clonus, which is rhythmic or regular. Myoclonus describes a medical sign and, generally, is not a diagnosis of a disease. It belongs to the hyperkinetic movement disorders, among tremor and chorea for example. These myoclonic twitches, jerks, or seizures are usually caused by sudden muscle contractions or brief lapses of contraction. The most common circumstance under which they occur is while falling asleep. Myoclonic jerks occur in healthy people and are experienced occasionally by everyone. However, when they appear with more persistence and become more widespread they can be a sign of various neurological disorders. Hiccups are a kind of myoclonic jerk specifically affecting the diaphragm. When a spasm is caused by another person it is known as a provoked spasm. Shuddering attacks in babies fall in this category.

Writer's cramp or focal hand dystonia (FHD) is an idiopathic movement disorder of adult onset, characterized by abnormal posturing and movement of the hand and/or forearm during tasks requiring skilled hand use, such as writing. Overcontraction of affected muscles, cocontraction of agonist and antagonist pairs, and activation of muscles inappropriate to a task all impair use of the affected hand.

<span class="mw-page-title-main">Dystonia</span> Neurological movement disorder

Dystonia is a neurological hyperkinetic movement disorder in which sustained or repetitive muscle contractions occur involuntarily, resulting in twisting and repetitive movements or abnormal fixed postures. The movements may resemble a tremor. Dystonia is often intensified or exacerbated by physical activity, and symptoms may progress into adjacent muscles.

<span class="mw-page-title-main">Athetosis</span> Condition of uncontrolled writhing movements

Athetosis is a symptom characterized by slow, involuntary, convoluted, writhing movements of the fingers, hands, toes, and feet and in some cases, arms, legs, neck and tongue. Movements typical of athetosis are sometimes called athetoid movements. Lesions to the brain are most often the direct cause of the symptoms, particularly to the corpus striatum. This symptom does not occur alone and is often accompanied by the symptoms of cerebral palsy, as it is often a result of this physical disability. Treatments for athetosis are not very effective, and in most cases are simply aimed at managing the uncontrollable movement, rather than the cause itself.

<span class="mw-page-title-main">Hyperkinesia</span> Excessive movements due to basal ganglia dysfunction

Hyperkinesia refers to an increase in muscular activity that can result in excessive abnormal movements, excessive normal movements, or a combination of both. Hyperkinesia is a state of excessive restlessness which is featured in a large variety of disorders that affect the ability to control motor movement, such as Huntington's disease. It is the opposite of hypokinesia, which refers to decreased bodily movement, as commonly manifested in Parkinson's disease.

Torsion dystonia, also known as dystonia musculorum deformans, is a disease characterized by painful muscle contractions resulting in uncontrollable distortions. This specific type of dystonia is frequently found in children, with symptoms starting around the ages of 11 or 12. It commonly begins with contractions in one general area such as an arm or a leg that continue to progress throughout the rest of the body. It takes roughly 5 years for the symptoms to completely progress to a debilitating state.

<span class="mw-page-title-main">Stiff-person syndrome</span> Neurological disorder

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<span class="mw-page-title-main">Monoplegia</span> Paralysis of a single limb

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<span class="mw-page-title-main">Spasmodic torticollis</span> Medical condition

Spasmodic torticollis is an extremely painful chronic neurological movement disorder causing the neck to involuntarily turn to the left, right, upwards, and/or downwards. The condition is also referred to as "cervical dystonia". Both agonist and antagonist muscles contract simultaneously during dystonic movement. Causes of the disorder are predominantly idiopathic. A small number of patients develop the disorder as a result of another disorder or disease. Most patients first experience symptoms midlife. The most common treatment for spasmodic torticollis is the use of botulinum toxin type A.

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<span class="mw-page-title-main">Meige's syndrome</span> Medical condition

Meige's syndrome is a type of dystonia. It is also known as Brueghel's syndrome and oral facial dystonia. It is actually a combination of two forms of dystonia, blepharospasm and oromandibular dystonia (OMD).

Myoclonic dystonia or Myoclonus dystonia syndrome is a rare movement disorder that induces spontaneous muscle contraction causing abnormal posture. The prevalence of myoclonus dystonia has not been reported, however, this disorder falls under the umbrella of movement disorders which affect thousands worldwide. Myoclonus dystonia results from mutations in the SGCE gene coding for an integral membrane protein found in both neurons and muscle fibers. Those suffering from this disease exhibit symptoms of rapid, jerky movements of the upper limbs (myoclonus), as well as distortion of the body's orientation due to simultaneous activation of agonist and antagonist muscles (dystonia).

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Joaquin Farias is a Spanish-born Canadian neuroscientist, researcher, and writer specializing in movement therapy for dystonia.

References

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Sources

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