Clinical and genetic evaluation of eight Brazilian families with spinocerebellar ataxia type 10

THESES

Clinical and genetic evaluation of eight Brazilian families with spinocerebellar ataxia type 10(Abstract)^*. Thesis. Curitiba, 2004

Hélio Afonso Ghizoni Teve^**

Spinocerebellar ataxia type 10 (SCA10) is an autosomal dominant ataxia caused by an expansion of a pentanucleotide (ATTCT) repeat in an intron of the SCA10 gene on chromosome 22. SCA10 has been previously reported only in Mexican families, in which the disease presented with a unique combination of pure cerebellar ataxia and epilepsy. So far, SCA 10 has not been reported in a non-Mexican population. Thus, this may very well be the first description of SCA 10 series outside Mexico.

We report on 47 patients with the SCA10 mutation on 8 new Brazilian families. All patients showed pure cerebellar ataxia without epilepsy, suggesting a different phenotype of the SCA 10 mutation in Brazilian families, when compared to their Mexican counterparts.

Cerebellar ataxia (gait ataxia, dysarthria and nystagmus) was seen in all Brazilian patients, whereas saccadic eye movement dysmetria was present in 76.6% of this population. Brisk deep tendon reflexes and lower limbs spasticity were observed in 10.63% and 6.38%, respectively. Peripheral neuropathy was not diagnosed in the Brazilian series.

Patients became symptomatic at the mean age of 35 years old and their illness last an average of 13.59 years.

Neuroimaging studies displayed signs of cerebellar atrophy in all cases. Molecular genetic studies showed an expansion repeat (ATTCT) on gene SCA 10, between 1350 and 2370, with an average of 1820. A correlation between age of clinical onset and type of expansion could be clearly established, as follows: the earlier the clinical onset, the longer the expansion (r=0,44, t=2,5). There is a difference between the average size of expansions in Brazilian (1820) and Mexican (2838) families.

Comparison between SCA 10, SCA 3 and other SCA patients revealed distinguished clinical features. In SCA 10 cases the phenotype is rather peculiar, including pure cerebellar ataxia and saccadic eye movement dysmetria. SCA 3 patients, on their turn, show cerebellar ataxia, ophthalmoplegia, diplopia, eyelid retraction, facial fasciculation, pyramidal signs and peripheral neuropathy.

Key words: spinocerebellar ataxia type 10, autosomal dominant cerebellar ataxia, pure cerebellar ataxia.

Publication Dates

• Publication in this collection
  02 Mar 2006
• Date of issue
  Sept 2005