Good Practice Guide


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Early onset inherited or idiopathic dystonias

Early onset dystonias tend to be generalised. Many are of known genetic origin. There are currently more than 20 known types of dystonia caused by gene mutations. Some of these affect children including:

  • A mutation in the DYT1 gene which causes generalised dystonia
  • A mutation in the DYT5 gene which causes dopa-responsive dystonia which is treatable with L-dopa

The majority of genetic forms of dystonia are autosomal dominant although some types of genetic dystonia occur in an autosomal recessive or x linked manner. Heritable childhood onset dystonia is more common amongst some ethnic groups (for instance DYT1 dystonia is more common in Ashkenazi Jewish people).

If a parent is found to be positive for a DYT1 gene mutation, this does not mean that their children will automatically get dystonia. The child may not inherit the gene and, even if the child does inherit the gene, the penetrance is only around 30%. It is important for the parents to speak to a geneticist before any decisions are made about future children, in order to be able to make an informed decision.

Children and young people with early-onset motor symptoms of genetic disorders such as dystonia-myoclonus (DYT11) and benign hereditary chorea (TITF1) may inadvertently be suspected of exhibiting features of attention-deficit hyperactivity disorder (ADHD) because of their apparent ‘fidgetiness’.

Inherited dystonias are relatively rare and their prevalence is dwarfed by that of children with acquired dystonia manifesting in infancy.

Early onset acquired dystonias

Early onset acquired dystonia can result from a wide variety of neurological conditions, inherited metabolic defects or environmental causes.

Environmental causes include disorders associated with reproductive casualty such as premature birth, perinatal brain damage (including birth asphyxia, also known as hypoxic ischaemic encephalopathy, and perinatal jaundice, also known as kernicterus), head trauma, hypoxia and haemorrhage and a variety of drugs or toxins that affect the basal ganglia, thalamus or brain stem. At least 15% of children and young people who have cerebral palsy may have persistent dystonic symptoms (Carr 2009). Dystonic symptoms may be overlooked and underdiagnosed
(Lin, 2011; McClelland 2011).

Making an appropriate diagnosis can be difficult in children with normal brain imaging. Such normal imaging may be found in up to 20% of children diagnosed with cerebral palsy (Korzeniewski 2008) but normal scans may be found in up to 50% of children with dystonia of prematurity (Towsley 2011). However ‘normal imaging’ may prompt the need for a search for a neurometabolic or genetic cause of dystonia or may reflect the lack of power for current imaging techniques to detect small changes.

Dystonia symptoms may be associated with other hereditary neurological syndromes such as Huntington’s disease, Wilson's disease and Ataxia telangiectasia. Metabolic disorders causing acquired dystonia include Lesch-Nyhan syndrome, Niemann-Pick disease, Leigh's disease and neurodegeneration with brain iron accumulation (NBIA): and newly described forms of NBIA such as BPAN (see Hayflick 2013).

A relatively new class of causes of dystonias in childhood are the ‘interferonopathies’ producing infantile, late infantile and childhood nigrostriatal necrosis such as Aicardi-Gouttierres Syndrome Type 6 (Rice 2012) and other interferon-related biomarkers (Rice 2013) opening up a whole new spectrum of progressive dystonias with possible new therapeutic approaches.

Autoimmune mechanisms of dystonia are increasingly recognised in children and young people under 20 years of age, including other acute movement disorders such as chorea and myoclonus with and without neuroimaging changes (Hacohen 2012, 2013). Untreated in the acute phase of the illness, these autoimmune encephalopathies can result in long-standing and often very disabling movement disorders, for instance after herpes simplex type 1 encephalitis (Hacohen 2013).

Although many of these conditions are very rare (Edwards, Quinn & Bhatia 2008) in adult practice they are collectively more common in children’s hospitals with neurological, neurodisability and metabolic services.

Age at onset, co-morbidities and progression in early onset dystonia

The following information is based on a cohort of 279 children referred to a UK specialist paediatric movement disorder service including 18% children with inherited / idiopathic dystonia, 72% non-progressive acquired dystonia and 10% hederodegenerative dystonia.

Median onset ages in this cohort were 3 years for inherited / idiopathic dystonia and 0.25 years for acquired dystonias. Only 33% of the children experienced a period of normal motor development.

In this sample, co-morbidities were identified in 63% of all cases and spasticity co-morbidity was present in 34% of children with acquired dystonia.

At referral (which was median 4.8 years after onset for inherited / idiopathic dystonia and 7.8 years after onset for acquired dystonia), carers perceived dystonia deterioration in 60% of cases, stabilisation in 32% and improvement in 8% (Lin 2014).

Last reviewed April 2014

Disclaimer
The Dystonia Society provides the information on this page as general information only. It is not intended to provide instruction and you should not rely on this information to determine diagnosis, prognosis or a course of treatment. It should not be used in place of a professional consultation with a doctor.
The Dystonia Society is not responsible for the consequences of your decisions resulting from the use of this information, including, but not limited to, your choosing to seek or not to seek professional medical care, or from choosing or not choosing specific treatment based on the information. You should not disregard the advice of your physician or other qualified health care provider because of any information you receive from us. If you have any health care questions, please consult the relevant medical practitioner.

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