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Other primary dystonias (dystonia-plus syndromes) 

Other primary dystonias (dystonia-plus syndromes)
Chapter:
Other primary dystonias (dystonia-plus syndromes)
Author(s):

Ivan Donaldson

, C. David Marsden

, Susanne A. Schneider

, and Kailash P. Bhatia

DOI:
10.1093/med/9780192619112.003.0952
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date: 06 June 2020

This chapter describes the characteristics of other primary dystonias (dystonia-plus syndromes), including where appropriate their historical backgrounds, classification, pathology, investigation and management; focus is on dopa-responsive dysktonia and myoclonic dystonia. Dystonia with marked diurnal fluctuation (dopa-responsive dystonia) has no accepted precise clinical definition. The disorder, however, is characterized by several features including 1) dystonia commencing in childhood or adolescence, usually in the lower limbs, 2) the appearance of parkinson-like features, and 3) dramatic improvement with l -dopa administration.

To this may now be added the presence of the abnormal gene(s), as it has been found that the disorder is due to a defective gene on chromosome 14q at the site of the for the enzyme guanosine triphosphate (GTP) cyclohydrase 1. The concentration of the major metabolite of dopamine, homovanillic acid (HVA), has been reported to be reduced in the cerebrospinal fluid (CSF) in dopa-reponsive dystonia (Ouvrier 1978, Fink et al. 1988) and to show a dramatic increase with l –dopa administration (Ouvrier 1978). Electromyography shows changes similar to other types of dystonia.

Thus, during involuntary dystonic movements and on attempted voluntary activity, there is activation of antagonists as well as agonists and this spreads to involve muscle groups other than those needed to carry out the action. Unlike most other dystonic disorders, this condition responds dramatically to l -dopa administration and patients may even appear normal. A small initial dose should be given and gradually increased until optimum improvement occurs.

In 1926 Davidenkow described the association of shock-like myoclonic jerks and slow involuntary movements which commenced in two siblings in their fifth decade. He entitled this ‘subacute hereditary myoclonic dystonia’. Myoclonic dystonia is in many (but not all) patients due to mutations

in the epsilon sarcoglycan gene (SGCE, DYT11) and is characterized by: 1) dominant mode of heritance, 2) childhood onset of myoclonus and dystonia, which particularly involves upper limbs and neck, 3) absence of other major neurological abnormality, and 4) marked relief of involuntary movements with alcohol ingestion. Onset occurs in childhood, frequently between 2 and 5 years of age, with regular myoclonic or ‘lightning-like’ jerks. These are usually spontaneous but can sometimes be provoked by auditory, visual, or tactile startle. The movements may be symmetrical or asymmetrical and synchronous or asynchronous. The arms and neck are usually affected first and remain the most prominently affected regions. The trunk may also develop such movements, but lower limbs are spared or only slightly involved. These jerks are frequently exacerbated by menstruation. Myoclonus may respond to clonazepam, alcohol treatment is often effective but may lead to addiction. Rapid-onset dystonia-parkinsonism, X-linked dystonia-parkinsonism and dystonia in benign hereditary chorea are also discussed.

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