Patients with cerebellar ataxia made riskier decisions than controls, suggesting this may be a unique cerebellar cognitive symptom.
In a recently published cross-sectional study in Parkinsonism & Related Disorders, findings showed significantly worse performance with the Iowa Gambling Task (IGT) in patients with cerebellar ataxia (CA) compared with the controls.1 These results suggest that impaired decision making is a distinctive cognitive symptom in CA.
In a cohort of 60 patients with CA, IGT total scores were significantly lower than the controls (-5.30 [±37.53] vs. 21.30 [±37.37], P = .004). Additionally, IGT total scores observed in patients with CA did not correlate with ataxia severity, measured by Scale of Assessment and Rating of Ataxia (SARA) scores (Pearson r = −0.02, P = .922) or with depressive symptoms, measured by Patient Health Questionnaire-9 (PHQ-9) scores (Pearson r = 0.19, P = .182).
Senior author Sheng-Han Kuo, MD, associate professor of neurology at Columbia University Irving Medical Center, told NeurologyLive®, “It’s a newly recognized symptom for cerebellar ataxia. Therefore, early recognition may lead to proper treatment and intervention for this population.”
Among the participants with CA recruited from the Ataxia Clinic at Columbia University Medical Center, 33 patients had genetic ataxia whereas 27 had non-genetic ataxia. Participants enrolled had a prior or comorbid neurologic or psychiatric disorder associated with impulsivity. Those enrolled completed the IGT online and had performance in each of the five 20-trial blocks compared between groups.2
The progression of patients' performance was also assessed using simple linear regression models and subgroup analyses were conducted with both genetic and non-genetic patients with CA. The severity of motor dysfunction in ataxia was measured with the SARA (n = 37) and symptoms of depression were determined using the PHQ-9 (n = 51).3,4
In an AVOVA, the IGT scores had a significant main effect of group (F = 10.07, P = .002) and a significant main effect of block (F = 10.14, P <.001), but no interaction between group and block (F = 1.22, P = 0.303). When separating each block, patients with CA had lower IGT scores in all blocks (CA cases vs. controls: Block 1: −3.77 [±6.68] vs. −0.40 [±6.46], P = .022; Block 2: −1.40 [±8.70] vs. 4.33 [±8.24], P = .005; Block 3: −0.12 [±9.79] vs. 5.87 [±9.14], P = 0.011; Block 4: 0.57 [±9.86] vs. 4.90 [±11.35], P = .112; Block 5: −0.58 [±10.63] vs. 6.60 [±10.25], P = 0.006), which showed that patients with CA made riskier decisions consistently throughout the task.
In the linear regressions, IGT scores across blocks demonstrated a slope of 1.46 (±0.53; P= .007) for controls and a slope of 0.83 (±0.38;P = 0.028) for patients with CA, indicating that both groups improved over time in their IGT scores. In a one-way ANOVA, a significant difference was observed between the IGT total scores of controls, patients with genetic ataxia, and patients with non-genetic ataxia (F = 4.98, P = .009). Also, in a post-hoc analyses, controls (21.30 [±37.37]) had higher IGT scores than both genetic and non-genetic CA, whereas no difference was shown between genetic and non-genetic CA. (−5.33 [±35.90] vs. −5.26 [±40.13], P >.999).
“There are ample of research, being cited in the paper, that the cerebellum has been found to be important for reward processing and modulation in animal models. Specifically, the cerebellum and ventral tag mental area connections is important to modulate the reward signals. In addition, several types of neurons in the cerebellum can encode the reward signals as well. Our data support that the decision making deficits may be the consequences of reward processing impairment,” Kuo added.
As for the limitations, participants with CA were of a heterogenous patient population which limits the possibility that other brain regions contributed to risky decision making. In addition, 100 trials may not be sufficient to observe subtle differences with performance in the IGT, as patients with CA and controls in this study had similar learning curves to those trials.
In prior research, patients with CA have been observed to be more impulsive and compulsive than controls in behaviors including gambling, hobbyism-punding, and excessive medication use.5,6 Investigators noted that future studies could further the understanding of the mechanisms underlying impaired decision-making in CA and broaden the spectrum of cerebellar cognitive affective syndrome.
“Clinicians should have a high suspicion of impulsive and compulsive symptoms for patients with cerebellar ataxia. Iowa Gambling Task may be used to detect more subtle decision making deficits in patients. In addition, we recently published the Cerebellar Impulsivity and Compulsivity Scales with a good sensitivity and specificity, which can be used in bedside,” Kuo said.