Early-onset generalized dystonia is characterized by the twisting of the limbs, specifically the foot and leg or hand and arm. The spasms may spread to involve twisting contractions of other parts of the body.
Early onset dystonia can be broadly divided into two major categories: DYT1 early onset generalized dystonia and non-DYT1 early onset dystonia. The distinction is that DYT1 generalized dystonia is known to be caused by a specific mutation in the DYT1 gene. However, not all primary generalized dystonias that begin in childhood are caused by this specific mutation in this gene. These forms are simply referred to as non-DYT1 generalized dystonia.
DYT1 dystonia is primary. Non-DYT1 dystonia may be primary or secondary.
Terms used to describe DYT1 generalized dystonia include: Oppenheim’s dystonia, primary torsion dystonia, early onset dystonia, childhood onset dystonia, idiopathic torsion dystonia. Lesser-used terms include: dystonia musculum deformans
Terms used to describe non-DYT1 generalized dystonia include: Primary torsion dystonia, early onset dystonia, childhood onset dystonia, idiopathic torsion dystonia. Lesser-used terms include: dystonia musculorum deformans
Historically, early-onset generalized dystonia has also been referred to as idiopathic torsion dystonia and dystonia musculorum deformans.
Symptoms of early-onset generalized dystonia can include:
• Twisted postures, for example in the torso or limbs
• Turning in of the foot or arm
• Muscle spasms, with or without pain
• Unusual walking with bending and twisting of the torso
• Rapid, sometimes rhythmic, jerking movements (often “myoclonic jerks”)
• Progression of symptoms leading to areas of the body remaining in sustained or fixed postures
Symptoms often begin in one area of the body and spread to other areas. Factors such as age and the part of the body where symptoms begin play a significant role in the progression. The younger the age of onset, the more likely the dystonic symptoms will begin in one of the legs, spread upward to other areas, and possibly become generalized. However, if symptoms begin in the arm or neck, the progression to other body areas may be less likely. The age of onset varies, but the peak period is between the ages of seven and ten years with symptoms progressing, then stabilizing, within a five-year period.
Symptoms commonly begin with a specific action and are not present at rest. For example, if symptoms begin in one leg, they may only be present when walking and disappear when the individual runs or walks backwards.
In generalized dystonia that begins in the arm, symptoms may be task-specific, i.e. apparent only during specific activities such as writing or playing a musical instrument. If the disorder progresses, the symptoms of arm dystonia may appear when another part of the body is engaged in voluntary motor activity. If the dystonia spreads to involve parts of the body other than then limb of onset, it will first move to adjacent segments of the body and then outward to areas farther from the site where symptoms began.
Dystonia is usually present continually throughout the day whenever the affected body part is in use and may disappear with sleep.
Features such as cognition, strength, and the senses, including vision and hearing, are normal. While is a chronic disorder, it is not fatal.
Most—but not all—people with early onset generalized dystonia have a specific genetic mutation. The gene responsible for early-onset generalized dystonia, termed DYT1, was discovered in 1997. Early onset generalized dystonia of this kind may be referred to as DYT1 dystonia or Oppenheim’s dystonia. (Generalized forms of dystonia that occur in childhood with no mutation in the DYT1 gene may simply be called non-DYT1 early onset generalized dystonia.)
The mode of inheritance for DYT1 dystonia is autosomal dominant. This means that a person only needs to inherit the mutation from one parent to develop symptoms. For reasons scientists do not yet understand, approximately 30% of persons who inherit the DYT1 mutation will develop dystonia. This means that 70% of persons who inherit the abnormal gene never develop symptoms. If an individual inherits the DYT1 mutation but does not develop symptoms by age 30, symptoms may never develop. There is no way yet to predict whether a person with the abnormal gene will develop symptoms of the disorder. Also, the severity may differ markedly from person to person, including family members.
The DYT1 gene mutation may also be referred to as a “GAG deletion,” referring to the specific section of DNA that is missing. Exactly how the abnormal gene causes dystonia is presently unknown, and a major focus of research efforts.
For persons with early onset generalized dystonia who do not have the DYT1 mutation, the cause is presumed to be primary, meaning that there is some genetic component that has yet to be identified. Secondary forms of generalized dystonia, such as dystonia secondary to cerebral palsy, may also begin in childhood.
The diagnosis of early onset generalized dystonia is not made by one definitive test, but rather primarily by information from the individual and the physical and neurological examination. In most cases, assorted laboratory tests are normal and used to rule out other disorders.
A genetic test is available to detect the DYT1 gene mutation to confirm a DYT1 dystonia diagnosis.
Oral medications are often the mainstay of treatment for early onset generalized dystonia, both DYT1 and non-DYT1 forms. Although there is no single drug that helps an overwhelming number of individuals, there are many that may be of benefit. These oral medications include levodopa, trihexyphenidyl, benztropine, diazepam, lorazepam, clonazepam, baclofen (oral and intrathecal—especially for dystonia and spasticity), carbamazepine, tetrabenazine (with lithium), and triple therapy such as a “cocktail” that includes tetrabenazine, fluphenazine, and trihexyphenidyl.
Botulinum toxin injections can be used to treat specific body parts that may be affected, such as the neck, jaw, hands, or feet.
Several surgical techniques may be appropriate for select individuals who do not respond to medications and botulinum toxin injections. These include ablative surgeries such as pallidotomy and thalamotomy, intrathecal baclofen, and deep brain stimulation.
Complementary therapies may be explored, particularly physical therapy, aquatic physical therapy, and regular relaxation techniques.