Cerebellar ataxia: definition
Cerebellar ataxias represent a heterogeneous group of diseases that identify precise cerebellar syndromes: the cerebellar forms, like all ataxias, frame neurodegenerative disorders, responsible not only for the progressive motor uncoordination of the lower and upper limbs, but also for involuntary ocular wave movements (oculomotor defects) and difficulty in articulating the word (dysarthria). Cerebellar ataxias are genetically transmitted, in an autosomal-dominant, autosomal-recessive, or X-linked manner; they are classified according to the mutated gene, the affected chromosomal locus or, again, based on the mode of genetic transmission of the ataxic syndrome.
Incidence
The medical statistics report interesting data on the incidence of cerebellar ataxia. Distinguishing the dominant transmission forms from the recessive ones, the latter seem to be much more frequent; in fact, autosomal-dominant cerebellar ataxia affects 0.8-3.5 subjects per 100, 000 healthy individuals, while autosomal-recessive cerebellar ataxia occurs in approximately 7 cases per 100, 000. Another difference between the two forms of genetic transmission is the onset of the disease: the autosomal-dominant forms tend to present themselves late, around 30-50 or even 60 years. The cerebellar ataxias with autosomal-recessive transmission tend instead to begin around 20 years of age.
Symptoms
The disease begins with walking and postural deficits, and with difficulty in coordinating joint movements; subsequently, cerebellar ataxia evolves in the negative sense, causing serious damage to the eye, such as optic atrophy, nystagmus, pupil abnormalities, retinitis pigmentosa (it starts first with reduced vision, and then creates night blindness in the forms of severity) and ophthalmoplegia (paralysis of the eyeball musculature). Other notable symptoms include: cerebellum hypoplasia, hyporeflexia, asthma, emphysema, muscle spasticity, diabetes, speech impairment and behavioral disorders. [taken from www.atassia.it/]
However, these symptoms do not always occur in all patients with cerebellar ataxia; in some cases, in fact, the eye disorders are absent, in others the degenerative damage involves only the cerebellum, in others the lesions can affect the retina, the optic nerve, the basal ganglia, the cerebellum etc. The symptom picture can sometimes be confused with Friedreich's ataxia; for this reason, the diagnosis must be correct and careful.
Causes
The causes of cerebellar ataxia transmission lie in genetics and gene mutation:
- Instability of expanded alleles, which causes early onset of cerebellar ataxia;
- Abnormal expansion of repeated nucleotide triplets (especially for forms with autosomal-dominant transmission);
- Mutation against apratassin or frataxin.
A certain correlation has also been observed between cerebellar ataxia and vitamin E deficiency. Some forms of cerebellar ataxia are also associated with hypogonadotropic hypogonadism, celiac disease, neoplasms, inflammatory and vascular lesions of the cerebellum.
Diagnosis and treatment
The neurological examination is certainly the most effective diagnostic option for identifying the symptoms of cerebellar ataxia; the neurological test must also be accompanied by a brain MRI. Blood tests are also recommended in order to ascertain the hereditary form. Molecular tests are useful for the recognition of the mutated gene.
Unfortunately, although scientific research has made great strides in the molecular field, the therapy aimed at fighting cerebellar ataxia has not yet been identified. However, there are palliative therapies, able to dampen the symptoms: physiotherapy helps, in fact, to alleviate pain and improve the quality of life of the ataxic patient [from www.telethon.it]
