Founder Effects of Spinocerebellar Ataxias in the American Continents and the Caribbean

Spinocerebellar ataxias (SCAs) comprise a heterogeneous group of autosomal dominant disorders. The relative frequency of the different SCA subtypes varies broadly among different geographical and ethnic groups as result of genetic drifts. This review aims to provide an update regarding SCA founders in the American continents and the Caribbean as well as to discuss characteristics of these populations. Clusters of SCAs were detected in Eastern regions of Cuba for SCA2, in South Brazil for SCA3/MJD, and in Southeast regions of Mexico for SCA7. Prevalence rates were obtained and reached 154 (municipality of Báguano, Cuba), 166 (General Câmara, Brazil), and 423 (Tlaltetela, Mexico) patients/100,000 for SCA2, SCA3/MJD, and SCA7, respectively. In contrast, the scattered families with spinocerebellar ataxia type 10 (SCA10) reported all over North and South Americas have been associated to a common Native American ancestry that may have risen in East Asia and migrated to Americas 10,000 to 20,000 years ago. The comprehensive review showed that for each of these SCAs corresponded at least the development of one study group with a large production of scientific evidence often generalizable to all carriers of these conditions. Clusters of SCA populations in the American continents and the Caribbean provide unusual opportunity to gain insights into clinical and genetic characteristics of these disorders. Furthermore, the presence of large populations of patients living close to study centers can favor the development of meaningful clinical trials, which will impact on therapies and on quality of life of SCA carriers worldwide.

Is fatigue an important finding in patients with spinocerebellar ataxia type 10 (SCA10)?

Spinocerebellar ataxia type 10 (SCA10) is a rare dominantly inherited neurodegenerative disorder characterized by cerebellar ataxia, dysarthria, ocular dysmetria, and seizures in some populations. Fatigue has been described in SCA1, SCA3, but has not been objectively investigated in SCA10. Our aim is to investigate the presence and related causal factors of fatigue among SCA10 patients. Twenty-eight patients with SCA10 and matched healthy controls were included and assessed using the Scale for the Assessment and Rating of Ataxia (SARA), Modified Fatigue Impact Scale (MFIS), Beck Inventory Depression (BDI) and Epworth Sleepiness Scale (ESS). Fatigue was evidenced in 32% of SCA10 versus 3.6% for the control group (p = 0.005). The following independent variables were not significant predictors for MFIS-BR: duration of disease, SARA and BSS. Age at onset of disease (r = -0.307, p = 0.021) and EDS (r = -0.347, p = 0.014) were mild to moderate predictors of fatigue. Similar to other SCAs, fatigue is common in SCA10 patients, suggesting a possible role of a common topographic degenerative pattern in its pathophysiology.

Nonmotor Symptoms in Patients with Spinocerebellar Ataxia Type 10

Nonmotor symptoms (NMS) have been described in several neurodegenerative diseases but have not been systematically evaluated in spinocerebellar ataxia type 10 (SCA10). The objective of the study is to compare the frequency of NMS in patients with SCA10, Machado-Joseph disease (MJD), and healthy controls. Twenty-eight SCA10, 28 MJD, and 28 healthy subjects were prospectively assessed using validated screening tools for chronic pain, autonomic symptoms, fatigue, sleep disturbances, psychiatric disorders, and cognitive function. Chronic pain was present with similar prevalence among SCA10 patients and healthy controls but was more frequent in MJD. Similarly, autonomic symptoms were found in SCA10 in the same proportion of healthy individuals, while the MJD group had higher frequencies. Restless legs syndrome and REM sleep behavior disorder were uncommon in SCA10. The mean scores of excessive daytime sleepiness were worse in the SCA10 group. Scores of fatigue were higher in the SCA10 sample compared to healthy individuals, but better than in the MJD. Psychiatric disorders were generally more prevalent in both spinocerebellar ataxias than among healthy controls. The cognitive performance of healthy controls was better compared with SCA10 patients and MJD, which showed the worst scores. Although NMS were present among SCA10 patients in a higher proportion compared to healthy controls, they were more frequent and severe in MJD. In spite of these comparisons, we were able to identify NMS with significant functional impact in patients with SCA10, indicating the need for their systematic screening aiming at optimal treatment and improvement in quality of life.