Apraxia profiles predict general cognitive deficits in patients with biomarker-verified Alzheimer's pathology

BackgroundApraxia represents a core feature of Alzheimers disease, a neurodegenerative disorder associated with increased {beta}-amyloid plaques and tau deposition. However, descriptions of apraxic deficits in AD patients are still scarce. Here, we comprehensively investigate apraxia profiles and their impact on general cognitive deficits in patients with biomarker-verified Alzheimers pathology. MethodsWe characterized the frequency and patterns of apraxic deficits in patients with biomarker-verified Alzheimers pathology (n=45) using a battery of standardized apraxia tests. Demographic variables and apraxia scores were related to patients general cognitive impairment using hierarchical regression analyses. ResultsApraxic deficits were found in 78% of patients with biomarker-verified Alzheimers pathology. AD patients were more impaired in imitating finger gestures (than hand gestures: 76.6% vs. 87.8%, p < 0.001), and imitating complex hand movements (than single hand movements: 76.3% vs. 96.7%, p < 0.001), even when controlling for general cognitive impairment. Apraxia assessments explained about 60% of the variance related to the severity of general cognitive deficits, with deficits in pantomiming object use (beta coefficient: 0.55, p = 0.017) and imitating finger gestures (beta coefficient: -0.51, p < 0.001) being significant predictors of general cognitive impairment. ConclusionsThese findings underline the relevance of apraxia in patients with biomarker-verified Alzheimers pathology. Data revealed distinct apraxia profiles independent of patients general cognitive status and showed that praxis performance, especially apraxic deficits in pantomiming the use of objects and imitating finger gestures, predicts general cognitive functioning in Alzheimers disease. What is already known on this topicApraxic deficits have been commonly reported in patients with suspected Alzheimers disease (AD). Current diagnostic criteria of AD include disease-specific biomarkers (i.e., amyloid and tau) reflecting the neuropathological changes in AD. However, little is known about the prevalence and characteristics of apraxia in patients with biomarker-verified Alzheimers pathology. What this study addsIn a well-defined sample of patients with evidence of Alzheimers pathology based on positive amyloid and tau biomarkers in cerebrospinal fluid (CSF) or positron emission tomography (PET), apraxic deficits are common, show differential patterns even after controlling for general cognitive deficits, and account for variance in the severity of the patients general cognitive impairment. How this study might affect research, practice or policyThis study shows that in patients with biomarker-verified Alzheimers pathology apraxic deficits are a relevant symptom that can predict general cognitive performance in mild to moderate disease stages. Our results warrant further investigation into the neuropathology underlying apraxic deficits in Alzheimers disease by examining the relationship between apraxic deficits and regional amyloid and tau deposition in the brain.