Depression in Patients with Spinocerebellar Ataxia Type 3 (SCA3)

Abstract

We thank Saute et al. for their insightful letter commenting on our recent article in Cerebellum [1]. The data they obtained in their current study as well as the results of their previous study [2] further emphasize the relevance of depressive symptoms in spinocerebellar ataxia type 3 (SCA3) patients. Whereas our SCA3 group comprised 15 patients, representing one out of four SCA subgroups studied, Saute et al. focused on SCA3 and evaluated depressive symptoms in a group of 49 SCA3 patients, applying also the Beck Depression Inventory (BDI). Within this large group of SCA3 patients, a varying severity of depression was detected, including moderate and severe depression, whereas we found only mildly depressed mood in our SCA3 group with BDI. Our study revealed a major correlation of depressed mood with dominant hand performance and only a weak correlation with Scale for the Assessment and Rating of Ataxia (SARA) scores, which rather reflect disease severity in general than motor function alone. Saute et al. further demonstrated correlations of BDI scores to neurological disability as assessed by the Barthel Index [2], and now also to SARA scores. This does not necessarily represent conflicting data. First, the different results may simply be due to different group sizes, i.e., the trend obtained in our study might have reached significance given a larger number of patients. Second, we studied outpatients—thus patients whose mobility and severity of ataxia may differ substantially from those studied by Saute et al. This is supported by differences regarding disease duration and disease severity (SARA score) between both studies: Whereas our SCA3 group had on average a disease duration of 5.7±3.5 years and a SARA score of 8.2±6.4, Saute et al. investigated more severely affected patients (SARA score 14.5±7.5) with longer disease duration (9.96±6.4 years). Third, and most important, our data indicate that impairment of motor functions most relevant to performing everyday tasks (dominant hand) may be more important for self-reported mood than an overall measure of disease severity which includes also aspects of the disease, which have less direct effects on the routine activities of daily living. Saute et al. did not provide direct measures of motor function with different test instruments. It is possible that they also might have found stronger correlations to direct measures of motor function. Interestingly, Saute et al. did not find a correlation of BDI scores with CAG repeat expansion or regional brain volume. Thus, findings of both studies emphasize the relevance of Response Letter to the Letter to the Editor entitled “Depressive mood is associated with ataxic and non-ataxic neurological dysfunction in SCA3 patients” by Saute et al., commenting on our article recently published in Cerebellum (Klinke et al. Neuropsychological Features of Patients with Spinocerebellar Ataxia (SCA) Types 1, 2, 3, and 6. Cerebellum. 2010).