A Comparative Study of Tower of London Scoring Systems and Normative Data

Objective

Tower of London (ToL) is a planning ability task that includes multiple versions. The original ToL was developed by Shallice together with two scoring systems (ToL-SS). Another two ToL-SS were proposed by Anderson et al. and Krikorian et al. The purpose of this study is to provide normative data for four ToL-SS and explore the effects of demographic variables on ToL performance. Furthermore, we aimed to determine the discriminative validity of these ToL-SS in clinical samples.

Method

Four groups were included in the study: a normative sample of healthy adults (HC; n = 298); patients with Parkinson's disease with mild cognitive impairment (PD-MCI; n = 52) and without cognitive impairment (PD-ND; n = 57); and patients with schizophrenia (SCH; n = 28). The effects of demographic variables on ToL-SS were examined in the HC group. Between-groups comparisons of ToL-SS were conducted using regression analysis with dummy codes.

Results

All four ToL-SS were not significantly affected by age, whereas the effect of gender and education is not consistent. ToL-SS significantly (p < .05) differentiate HC from PD-MCI and SCH. Cohen's effect size coefficients d range from 0.68 to 1.29. Internal consistency coefficients (Cronbach's α) of ToL-SS range from 0.33 to 0.60.

Conclusions

Despite poor to questionable internal consistency of ToL-SS, the discriminative validity and clinical utility for assessing planning deficits in PD-MCI and SCH are high. This study provides normative standards for all four ToL-SS on an adult population for use in clinical practice.

Cognition in Parkinson's Disease

Cognitive decline is now recognized as a common nonmotor symptom of Parkinson's disease, and it has been the subject of increasing research in recent decades. Cognitive deficits in Parkinson's disease can be distinguished as dopaminergically mediated executive dysfunction seen in the milder stages vs a global dementia syndrome that can occur with disease progression. The neural basis of these deficits has been explored from the perspective of multimodal imaging techniques to measure the structural, functional, and metabolic correlates of cognitive decline in Parkinson's disease. Increasingly, changes in neurotransmitter systems beyond dopamine, including the noradrenergic, serotonergic, and cholinergic systems, are being recognized for their contribution to cognitive decline. The impact of certain genetic variations on cognitive function has also been established, including links between cognitive decline and polymorphisms affecting COMT, MAPT, APOE, and GBA genotypes. Although therapeutic options for cognitive decline are still far less established than for motor systems, both pharmacological and nonpharmacological strategies are continuing to develop.

Measuring functional impact of cognitive impairment: validation of the Parkinson's disease cognitive functional rating scale

BACKGROUND

Little is known on the impact of cognitive impairment on instrumental activities of daily living (IADL) in pre-dementia stages of Parkinson's disease (PD).

OBJECTIVE

To investigate the clinimetric properties, applicability and responsiveness of a brief questionnaire (twelve-item; maximum score = 24) for rating functional abnormalities associated to cognitive impairment in non-demented PD patients (ND-PD).

METHODS

Two studies were carried-out: (1) a clinimetric study validated the Parkinson's Disease-Cognitive Functional Rating Scale (PD-CFRS) against the Older Americans Resource Survey (OARS-IADL) in 53 ND-PD patients and 53 matched controls; (2) A prospective multicenter 6-month responsiveness study involving 120 ND-PD patients explored sensitivity to change.

RESULTS

In the clinimetric study the PD-CFRS showed intermediate concurrent validity (ICC = 0.50), high test-retest (ICC = 0.82), inter-rater reliability (ICC = 0.80) and internal consistency (Cronbach's α = 0.79), and higher coefficient of variation to detect dysfunction in ND-PD patients (PD-CFRS 86.6% vs. OARS-IADL 8.1%). There was a strong relationship between the PD-CFRS and the global cognitive status determined with the PD-Cognitive Rating Scale (r = -0.72, p < 0.0001). The responsiveness study recruited 63 patients with normal cognition and 57 with mild cognitive impairment (MCI); an increase of 2 points in the PD-CFRS after 6 months was associated with a clinically significant worsening of the cognitive functional status. According to a discriminant analysis a PD-CFRS cut-off score of ≥3 was found to be optimal for detecting functional impairment in PD-MCI patients.

CONCLUSIONS

Cognitive impairment exerts measurable impact on IADL in ND-PD patients that can be reliable measured with the PD-CFRS, a PD-validated instrument that can be useful in clinical and research settings.