Primary Torsion Dystonia
Primary torsion dystonia
Description, Causes and Risk Factors:
Primary torsion dystonia is a progressive movement disorder characterized by sustained, twisting muscle spasms. With time, the frequency and duration of these spasms increases, leading to joint contractures and progressive disability. Spasms may be slow or rapid shock-like jerks, which are repetitive and may be rhythmic, and which are often made worse by voluntary movement, stress and fatigue.
Individuals with primary torsion dystonia have normal early development and normal intelligence. Primary torsion dystonia is a clinically and genetically heterogeneous condition, age at onset is a relevant variable for the clinical presentation and the prognosis. The de?nition of early onset dystonia is based on the identi?cation of a threshold age to use for classifying patients. The age of 21 years has been originally set by a consensus of experts, but later observations have proposed to increase the threshold for this terminology up to 26 years. PTD may occur sporadically or in familial aggregation; one PTD gene (named DYT1) and three di?erent loci (named DYT6, DYT7, and DYT13) have been identi?ed. The natural history of PTD is characterized by focal onset and occasional spread to other body parts with a variable natural course. In adult-onset cases, dystonia usually remains restricted to a single body district or has a limited di?usion to other body regions; in patients with early onset dystonia the symptoms tend to generalize. DYT1 PTD is the best characterized form of dystonia; the typical DYT1 phenotype is with early limb onset, rapidly progressive course towards generalization, and no involvement of cranial segments. By contrast, limited data are available on the clinical features and the natural course of non-DYT1 dystonia, particularly in the European population.
Average age of onset and severity are variable. Individuals who experience onset in the foot or leg generally begin to do so by age 9, while those with onset in the arm begin by age 15, on average. If a person has not developed contractures by 30, they are unlikely to do so later in life. Overall, dystonia will spread into the limbs and torso in 60% to 70% of patients. About 11% to 18% of cases will experience dystonia in the cranial muscles.
Primary torsion dystonia was observed more frequentlyin women than in men. In all patientsonset was focal, most frequently a cranial dystonia(50.4%), followed by cervical (22.0%), upper limb(15.4%), laryngeal (8.3%) or lower limb dystonia(2.6%). Cranial onset was more frequently observed inwomen, whereas upper limb onset prevailed in men. Patients with cranial onsethad the highest mean age at disease onset. Patients with lower limb onset had thelowest age. Overall, age atdisease onset was lower in men than in women. Cranial and laryngealonset occurred earlier in men than in women, whereas upper limb onsetoccurred earlier in women.
RESEARCH: Four hundred and sixty records of patients with primary torsion dystonia (296 women and 164 men) were evaluated. The mean age at disease onset was 48.3 ± 17.7 years; 13 patients carried the DYT1 CAG deletion. The distribution of age at onset was represented by a bi-modal curve, with a nadir at 21 year separating early onset from late onset cases. In 15.9% of cases there was a positive family history of dystonia. Cranial, cervical or lower limb onset was more common amongst women (M:F ratios were 1:2.7, 1:1.9, and 1:3); by contrast, onset in the upper limb was more common in men (M:F ratio 2.2:1). As expected, disease progression was more pronounced in cases with early onset; it was reckoned that onset at or above 32 years was associated with a negligible likelihood to progress to a generalized form. The mean age at onset of familial cases was 44.8 ± 11.2 years, signi?cantly lower than the mean age at onset of sporadic cases (53.5 ± 13.4 years). Familial cases were characterized by more sites involved throughout disease course. Familial cases had a higher tendency to progress to a segmental or generalized form than sporadic cases.
Primary torsion dystonia is characterized by involuntary, repetitive, sustained muscle contractions. These contractions can cause twisting of the body, poor posture, difficulty grasping objects, cramps and foot drag. An arm or a leg is usually the first body part to be affected.
The severity of muscle contractions varies widely, even within affected families. Some people with primary torsion dystonia are incapacitated by their symptoms, while in others the only manifestation of the disease is writer's cramp. People who develop symptoms later in life tend to have more mild disease. Many people with primary torsion dystonia remain ambulatory throughout their lives and maintain a good quality of life.
No cognitive problems are associated with primary torsion dystonia.
If a young person develops symptoms typical of primary torsion dystonia, genetic testing can be used to confirm the diagnosis. In people over 26 years of age, genetic testing for DYT1 mutations is usually reserved for people who show signs of the disease and have a family history of early-onset primary torsion dystonia.
There are forms of dystonia (uncontrolled muscle contractions) other than primary torsion dystonia. These other forms can be caused by mutations in genes other than DYT1, or by non-genetic factors such as strokes, tumors, infections, drugs, toxins and metabolic disorders. The symptoms of early-onset Parkinson's can also mimic symptoms of primary torsion dystonia.
Therapy for most people with dystonia is symptomatic, directed at controlling the intensity of the dystonic contractions.
Early diagnosis and start of treatment for dystonia, though not proven to alter its course or increase the likelihood for remission, may improve quality of life and alleviate the disability of patients with dystonia.
Available therapies for dystonia include oral medications, intramuscular or subcutaneous botulinum toxin injections, surgical procedures, and physical and/or rehabilitation therapies.
Overall, about 40% of patients improve with oral therapy. Adverse effects of the particular agents used can limit the benefits.
Overall, the goals of therapy should be directed at increasing movement, alleviating pain, preventing contractures, restoring functional abilities, and minimizing adverse effects from medical therapy.
Although no curative treatment for dystonia is available, treatment of the underlying disorder may help reverse symptoms in patients with secondary forms of dystonia (eg, from Wilson disease or DRD).
NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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