Definition of dystonia
Dystonias constitute a heterogeneous group of motor-muscular disorders, unfortunately destined to often worsen during old age. The spasms and involuntary contractions of the musculature force the subject to assume uncomfortable, abnormal and bizarre positions, as well as postural, sometimes painful twists. Given the various types of dystonia currently diagnosed, this article will be devoted exclusively to the classification of dystonic forms.
General classification
Dystonia can be classified into three large groups, each of which is divided into further sub-categories, summarized below in the table *. Dystonias are cataloged according to:
- Localization, ie based on the interest of the various anatomical sites affected by dystonia (focal dystonia)
- Age of onset of movement disorder (generalized dystonia)
- Causative cause (secondary dystonia)
| Focal dystonias ** | Generalized dystonia | Secondary dystonia |
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Focal dystonia
We have classified various types of focal dystonias: these movement alterations seem to be typical of the adult and it is almost unlikely that infants will be affected. Given the complexity of the subject, the entire next chapter will be devoted to focal dystonia.
Generalized dystonia
The classification of dystonia is complex and it is not always possible to distinguish one form from another; so much so that some authors do not speak of generalized dystonia proper, but of generalized idiopathic dystonias, thus mixing in this category also secondary dystonic characters.
However, generalized forms have a much more violent and rapid onset than focal and segmental forms. Moreover, if the target of focal forms is represented by adults, children aged between 6 and 10 are more at risk of generalized dystonia. In 1988 a study was conducted (Fahn's case study) on a sample of 762 dystonic patients: it emerged that 14% of these had generalized dystonia, 52% focal dystonia and the remaining 34% multifocal-segmental dystonia.
It is believed that generalized dystonias perfectly frame the symptomatology of deforming muscular dystonia [taken from I gangli and movement disorders, by A. Albanese].
Secondary dystonia
As we have seen, idiopathic, symptomatic and iatrogenic dyskinesias are classified as secondary-type dystonia. In the symptomatic form, dyskinesia is not the only disorder present, since it is the consequence of degenerative-metabolic diseases, in which the nuclei of the brain base are involved; otherwise, in idiopathic dystonia, in which the triggering cause is not perfectly identified, involuntary muscle spasms represent the only symptom that can be diagnosed to the patient [taken from www.distonia.it]. The diagnosis of idiopathic type dystonias must be more precise, since the search for possible tremors, tics and motor hindrances is essential, considering the three most important spy factors of idiopathic forms. Recently, the gene implicated in the manifestation of fluctuating dystonia, a sub-category of idiopathic dystonia, has been identified.
The pathological evolution in the negative sense of idiopathic dystonia is defined, by many authors, as "stormy", when it appears for the first time during childhood and adolescence. With age, the symptoms of dystonia seem to stabilize and, in some patients, the disease seems to fade and alleviate symptoms.
