Dystonia: Pt. 3

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The neck muscles are affected most. Cervical dystonia can produce mild to severe symptoms. If muscle spasms and contractions are frequent and severe enough, the individual may also experience stiffness and pain. Dopa-responsive dystonia primarily affects the legs. Onset occurs from ages This type of dystonia responds well to levodopa, a dopamine medication. The most common symptom is a stiff, unusual walk, with the sole of the foot bent upwards. In some cases, the foot may turn outwards at the ankle. The individual experiences spasms in the muscles on one side of the face.

Symptoms may be more prominent when the individual is under mental stress or physically tired. The muscles in the voice box larynx spasm. People with laryngeal dystonia may sound very quiet and breathy when they speak, or strangled - depending on which way the muscle spasms in or out. This type of dystonia affects the jaw and mouth muscles. The mouth can pull outwards and upwards. Some individuals will only have symptoms when the muscles of the mouth and jaw are being used, while others may experience symptoms when the muscles are not in use.

Some individuals may have dysphagia problems swallowing. Writer's cramp involves uncontrollable cramps and movements in the arm and wrist. This is a task-specific dystonia, because it affects people who do a lot of writing before symptoms appear. Generalized dystonia normally affects children at the beginning of puberty. Symptoms generally occur in one of the limbs and eventually spread to other parts of the body.

In this rare version of dystonia, muscle spasms and abnormal body movements only happen at specific moments. A paroxysmal dystonia attack can look like epilepsy during a seizure fit. However, the individual does not lose consciousness and will be aware of their surroundings, unlike epilepsy. An attack can last for just a few minutes, but in some cases, may persist for several hours.

The following triggers may bring on an attack:.

Primary dystonia - not related to another condition. No cause can be identified. In primary dystonia, no underlying cause is identified. Experts believe it may be a problem with a part of the brain called the basal ganglia. This region is responsible for involuntary movements. It may be that not enough, or the wrong types of neurotransmitters are produced in the basal ganglia, resulting in primary dystonia symptoms. It is also possible that enough is produced, but not the right type for proper muscle function.

Researchers believe that other brain regions are also involved. This type of dystonia is caused by a combination of various conditions and diseases; for example:. Parkinson's disease is also a neurodegenerative condition that affects the same part of the brain as dystonia - the basal ganglia.

Because of this, both conditions can sometimes appear in the same individual.

Dystonia: Symptoms, causes, and types

Certain drugs can cause dystonia. Cases of drug-induced dystonia normally occur after just one exposure to a drug.

In general, this is relatively easy to treat successfully. However, sometimes, dystonia can develop after taking a drug for some time, this is called tardive dystonia; Tardive dystonia is most commonly caused by drugs called neuroleptics, which are used to treat psychiatric, gastric, and movement conditions.

Defining Dystonic Tremor

Drugs that can cause drug-induced dystonia include:. However, the doctor will need to carry out some tests and ask targeted questions to determine whether they have primary or secondary dystonia.

Blood and urine tests - to determine whether there are any toxins or infections, and to check organ function such as the liver. Genetic test - to check for faulty abnormal, mutated genes and rule out other conditions, such as Huntington's disease. MRI scan - to reveal brain damage or a tumor. Levodopa - if symptoms improve rapidly after taking levodopa, the doctor will most likely diagnose early-onset dystonia. People diagnosed with dopa-responsive dystonia will be prescribed levodopa treatment. This medication raises levels of dopamine - a neurotransmitter. People taking levodopa may initially experience nausea, which should ease and disappear after the body gets used to the drug.

This powerful poison, which is safe when administered in very small doses, is often used as a first-line treatment for most other types of dystonia. In this review, we summarize recent advances in understanding the etiology, risk factors and pathophysiology of focal task specific dystonia FTSD , movement disorders characterized by abnormal motor activation during the performance of specific, repetitive actions. Recently updated consensus opinion classifies dystonias by two axes: The first axis, clinical characteristics, includes the age of onset, affected body region, temporal pattern, and associated neurologic or systemic features [ 1 ].

A subclassification includes focal task specific dystonias FTSD , which are a diverse group of focal dystonias affecting an isolated body part and are triggered, at least initially, by a specific action. In , clerks in the British Civil Service were noted to develop difficulty with writing. Sport-related FTSD have also been described in golfers, pistol shooters and ping-pong players, among others.

We then discuss emerging findings on the etiology, pathophysiology and treatment of FTSD. FTSD typically begins in adulthood with symptom onset in the third to sixth decade. Unlike other adult onset primary focal dystonias, FTSD is more common in men, and it usually affects the arm, facial muscles or larynx [ 9 ]. Overall prevalence estimates for FTSD in the general population range from 7 to 69 per million [ 10 , 11 ]. FTSD typically presents as an insidious, painless loss of dexterity triggered by performance of a specific, often over-practiced task.

Symptoms progress over time to trigger uncontrolled activation of muscle groups, leading to abnormal postures and movements. Early in the disease course, the dystonia typically is triggered only by the performance of a specific task, but over time spreads to involve other tasks, or even spreads to previously unaffected areas of the body.

As with other types of dystonias, sensory tricks, or geste antagonistes , may temporarily reduce the dystonic symptoms of FTSD [ 14 ]. Typically, the distal muscles of the upper extremity are affected, but dystonia may progress to include more proximal muscle groups, may be triggered by other activities, and can even spread to the opposite non-dominant hand.

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Average age of onset is in the fourth decade, and once present, symptoms rarely remit [ 8 ]. FTSD seen in musicians, a group that may be at risk due to overly practiced fine motor tasks, typically manifests in two phenotypes based on the particular instrument: Dystonia typically occurs in the hand that performs the more demanding tasks, such as the right hand in pianists and the left hand in violinists [ 16 ].

The specific pattern of abnormal muscle activation varies by instrument. For example, abnormal flexion of the fingers is typically seen in pianists and violinists, while in woodwind or brass players, extension due to lumbrical activation can occur [ 15 ]. FTSD may be exquisitely task specific, triggered by playing one instrument, but sparing the hand when a patient plays a different instrument. Embouchure dystonia may affect brass and woodwind players, with age of onset in the fourth decade [ 6 ].

Embouchure dystonias may be further classified by the pattern of abnormal movements, including embouchure tremor, involuntary lip movements and jaw closure [ 6 ]. In recent years, much effort has focused on understanding the etiology, risk factors and pathophysiology of FTSD and potential therapeutic interventions. We will review these in turn. The etiology of FTSD remains unknown, although recent lines of evidence suggest that both genetic and environmental factors are important [ 17 ].

This finding suggests that reduced interhemispheric inhibition may serve as a possible endophenotypic marker of genetic susceptibility for developing FTSD [ 23 ]. In addition to repetitive, over-practicing of a motor task, other environmental factors may contribute to the risk factors of developing FTSD. Possible risk factors include personality traits, such as perfectionism and anxiety, anatomical factors, such as hand size and joint mobility, as well as delayed onset of age of musical training [ 17 , 24 , 25 ].

The pathophysiology of FTSD has been linked to abnormalities in inhibition, plasticity, and motor networks. Interestingly, this abnormality was found in the bilateral hemispheres of patients, despite unilateral symptoms. Recent research has therefore postulated that decreased SICI may not directly cause abnormal motor activation but rather facilitate the development of FTSD through other mechanisms [ 27 , 28 ].

Dystonia: Pt. 3

Specifically, one suggested mechanism, found in several studies of FTSD patients, is the development of impaired surround inhibition, a neural inhibitory mechanism responsible for the selective recruitment and activation of muscles necessary for a particular task with inactivation of the neighboring muscles that are unnecessary [ 27 , 29 , 30 ]. Another interesting abnormality that may contribute to FTSD pathology is maladaptive neural plasticity. While plasticity is believed to be critical to the processes of learning and memory, maladaptive neuroplastic responses in both the motor and sensory cortices have been examined in conditioning protocols using repetitive stimuli from TMS [ 34 ].

Such abnormalities included increased facilitation with spread to non-median nerve innervated muscles in addition to the absence of a typical cortical silent period [ 35 ]. Such aberrant somatotopy may be reversible with associated improved fine motor control using constraint-induced therapy [ 40 — 42 ]. However, another study of somatotopic mapping discovered bilateral misrepresentation of digits despite unilateral dystonic symptoms, suggesting that the disturbed somatotopy is an endophenotype for vulnerability to develop FTSD [ 43 ].

Regardless of the etiology of the aberrant somatotopy, the evidence suggests that maladaptive plasticity of FTSD impairs sensorimotor integration. Finally, results from recent investigations have suggested a network disorder leading to FTSD, whereby involvement of the entire sensorimotor network contributes to dystonia [ 44 ].

Cerebellar dysfunction has also been suggested to contribute to FTSD, although the specific abnormality is not well understood.

Introduction

Further research is warranted to understand the precise network abnormalities; however, evidence of aberrant connections between the basal ganglia and cerebellum leading to dystonia is supported by research demonstrating that interruption of this connection leads to improvement of the dystonic symptoms [ 52 ]. Current treatment modalities for FTSD include oral medication, chemodenervation, surgery and physical therapy. Anticholinergic agents like trihexyphenidyl, as well as other medications, such as primidone, baclofen, and phenytoin have been tried with inconsistent responses and frequent intolerable side effects [ 53 — 55 ].

Each of the seven known BoNT serotypes types A—G targets a specific SNARE protein for degradation in peripheral cholinergic neurons, thereby preventing the downstream release of acetylcholine into the neuromuscular junction. As a result, chemodenervation and subsequent muscle paralysis occur and persist for several months until the eventual degradation of BoNT and regeneration of SNARE proteins [ 56 ]. Treatment of limb dystonia with BoNT has demonstrated transient increased intracortical inhibition on par with normal levels of inhibition as measured by transcranial magnetic stimulation [ 62 ].

Furthermore, recent research suggests that BoNT may additionally have non-SNARE cellular targets involved in wide-ranging activities, such as cell division and apoptosis, neuritogenesis and gene expression [ 63 ]. Of the seven BoNT serotypes, only serotype A and to a lesser extent serotype B are available for clinical use, with specific formulations of each serotype characterized by different potency, immunogenicity, preparation, compound stability and heat tolerance.

Notably, BoNT type B is only formally approved for the treatment of cervical dystonia, while BoNT type A has approved indications in the treatment of both neurologic and non-neurologic conditions [ 64 ]. Multiple studies have demonstrated long-lasting treatment benefits of BoNT in FTSD, but there is a delicate balance between reducing dystonic symptoms without inducing concurrent residual weakness resulting in loss of motor function [ 53 , 65 — 68 ].

Even with treatment, many affected musicians are no longer able to play professionally, due to the high level of fine motor skill required for continued professional performance. In recent years, emerging studies have investigated the role of surgery and sensorimotor retraining as therapeutic options.

Thalamotomies have been performed as treatment of a variety of movement disorders since the s [ 69 ]. However, larger long-term follow-up studies will be necessary to evaluate the lasting efficacy of this intervention. Additionally, a small case series has investigated the role of deep brain stimulation DBS in the treatment of FTSD with promising results [ 73 ]. Given the invasive nature of both thalamotomies and DBS, these procedures have primarily been reserved for medically refractory cases.

Based on the idea of excessive motor excitability and aberrant sensorimotor integration in the development of FTSD, sensorimotor retraining may hold promise. Home Contact Us Help Free delivery worldwide. Description Diagnosis, Classification, and Pathophysiology of Dystonia: Product details Format Paperback 56 pages Dimensions x x 6mm Descartes' Error Antonio Damasio. Sensorimotor Control and Learning James Tresilian.

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