Matthew Rizzo

Vision and cognition in Alzheimer's disease.

Alzheimers disease (AD) is known to affect visual pathways, but potential concomitant effects on vision and cognitive performance are not well understood. We studied 43 individuals with AD of mild severity and 22 individuals without dementia on a battery of tests designed to measure multiple aspects of basic and higher-order visual perception and cognition. All subjects performed on the same visual and cognitive test batteries. The results showed no differences between groups on tests of static visual acuity, stereoacuity, dynamic visual acuity or motion direction discrimination. However, individuals with AD performed significantly worse on tests of static spatial contrast sensitivity, visual attention, shape-from-motion, color, visuospatial construction and visual memory. Correlation analyses showed strong relationships between visual and cognitive scores. The findings show that AD affects several aspects of vision and are compatible with the hypothesis that visual dysfunction in AD may contribute to performance decrements in other cognitive domains. The pattern of involvement indicates that AD affects multiple visual neural pathways and regions. It is possible that better understanding of vision-related dysfunction could aid diagnosis and interventions to improve functional capacity in patients with dementia.

Visual dysfunction in Parkinson disease without dementia

Objective: To determine the profiles of visual dysfunction and their relationship to motor and cognitive dysfunction and to disability in mild to moderate Parkinson disease (PD) without dementia. Methods: Seventy-six independently living participants with mild to moderate PD and 161 neurologically normal older adults were studied using a comprehensive battery to assess visual acuity, contrast sensitivity (CS), visual speed of processing and attention, spatial and motion perception, visual and verbal memory, visuoconstructional abilities, executive functions, depression, and motor function. Results: Participants with PD scored significantly worse on all tests of vision and cognition compared with normal elderly persons. Reduced CS contributed to deficits on tests of spatial and motion perception and attention in participants with PD. Impairments in visual attention and spatial perception predicted worse cognitive function. Worse performances on tests of visual speed of processing and attention, spatial and motion perception, visual construction, and executive functions correlated with measures of postural instability and gait difficulty (in the Motor section of the Unified Parkinsons Disease Rating Scale). Impairments in motor function, visual memory, mood, and executive functions predicted worse disability as measured by Schwab–England Activities of Daily Living Scale. Conclusions: Patients with mild to moderate Parkinson disease showed impaired visual perception and cognition compared with elderly control subjects. Visual dysfunction contributes to parkinsonian disability through its influences on cognition and locomotion.

Simulated Car Crashes at Intersections in Drivers With Alzheimer Disease

Current evidence suggests that car crashes in cognitively impaired older drivers often occur because of failure to notice other drivers at intersections. We tested whether licensed drivers with mild to moderate cognitive impairment due to Alzheimer disease (AD) are at greater risk for intersection crashes. In this experiment, 30 participants drove on a virtual highway in a simulator scenario where the approach to within 3.6 seconds of an intersection triggered an illegal incursion by another vehicle. To avoid collision with the incurring vehicle, the driver had to perceive, attend to, and interpret the roadway situation; formulate an evasive plan; and then exert appropriate action on the accelerator, brake, or steering controls, all under pressure of time. The results showed that 6 of 18 drivers with AD (33%) experienced crashes versus none of 12 nondemented drivers of similar age. Use of a visual tool that plots control over steering wheel position, brake and accelerator pedals, vehicle speed, and vehicle position during the 5 seconds preceding a crash event showed inattention and control responses that were either inappropriate or too slow. The findings were combined with those in another recent study of collision avoidance in drivers with AD that focused on potential rear end collisions. Predictors of crashes in the combined studies included visuospatial impairment, disordered attention, reduced processing of visual motion cues, and overall cognitive decline. The results help to specify the linkage between decline in certain cognitive domains and increased crash risk in AD and also support the use of high-fidelity simulation and neuropsychologic assessment in an effort to standardize the assessment of fitness to drive in persons with medical impairments.

Practice Parameter update: Evaluation and management of driving risk in dementia Report of the Quality Standards Subcommittee of the American Academy of Neurology

Objective: To review the evidence regarding the usefulness of patient demographic characteristics, driving history, and cognitive testing in predicting driving capability among patients with dementia and to determine the efficacy of driving risk reduction strategies. Methods: Systematic review of the literature using the American Academy of Neurologys evidence-based methods. Recommendations: For patients with dementia, consider the following characteristics useful for identifying patients at increased risk for unsafe driving: the Clinical Dementia Rating scale (Level A), a caregivers rating of a patients driving ability as marginal or unsafe (Level B), a history of crashes or traffic citations (Level C), reduced driving mileage or self-reported situational avoidance (Level C), Mini-Mental State Examination scores of 24 or less (Level C), and aggressive or impulsive personality characteristics (Level C). Consider the following characteristics not useful for identifying patients at increased risk for unsafe driving: a patients self-rating of safe driving ability (Level A) and lack of situational avoidance (Level C). There is insufficient evidence to support or refute the benefit of neuropsychological testing, after controlling for the presence and severity of dementia, or interventional strategies for drivers with dementia (Level U).

Predictors of driving safety in early Alzheimer disease

Objective: To measure the association of cognition, visual perception, and motor function with driving safety in Alzheimer disease (AD). Methods: Forty drivers with probable early AD (mean Mini-Mental State Examination score 26.5) and 115 elderly drivers without neurologic disease underwent a battery of cognitive, visual, and motor tests, and drove a standardized 35-mile route in urban and rural settings in an instrumented vehicle. A composite cognitive score (COGSTAT) was calculated for each subject based on eight neuropsychological tests. Driving safety errors were noted and classified by a driving expert based on video review. Results: Drivers with AD committed an average of 42.0 safety errors/drive (SD = 12.8), compared to an average of 33.2 (SD = 12.2) for drivers without AD (p < 0.0001); the most common errors were lane violations. Increased age was predictive of errors, with a mean of 2.3 more errors per drive observed for each 5-year age increment. After adjustment for age and gender, COGSTAT was a significant predictor of safety errors in subjects with AD, with a 4.1 increase in safety errors observed for a 1 SD decrease in cognitive function. Significant increases in safety errors were also found in subjects with AD with poorer scores on Benton Visual Retention Test, Complex Figure Test-Copy, Trail Making Subtest-A, and the Functional Reach Test. Conclusion: Drivers with Alzheimer disease (AD) exhibit a range of performance on tests of cognition, vision, and motor skills. Since these tests provide additional predictive value of driving performance beyond diagnosis alone, clinicians may use these tests to help predict whether a patient with AD can safely operate a motor vehicle. AD = Alzheimer disease; AVLT = Auditory Verbal Learning Test; Blocks = Block Design subtest; BVRT = Benton Visual Retention Test; CFT = Complex Figure Test; CI = confidence interval; COWA = Controlled Oral Word Association; CS = contrast sensitivity; FVA = far visual acuity; JLO = Judgment of Line Orientation; MCI = mild cognitive impairment; MMSE = Mini-Mental State Examination; NVA = near visual acuity; SFM = structure from motion; TMT = Trail-Making Test; UFOV = Useful Field of View.

Visual attention impairments in Alzheimer's disease.

Background: Impaired attention can hinder information processing at multiple levels and may explain aspects of functional decline in aging and dementia. Impairments of attention in early AD may contribute to performance reductions in other cognitive domains, including memory and executive functions. Method: The authors analyzed the scores on a battery of tests of attention and cognitive abilities in 64 older individuals: 42 with mild AD and 22 control subjects without dementia. The authors tested the hypotheses that patients with AD would have impairments of visual attention, and that these impairments would correlate with dysfunction in other key cognitive domains. Results: Patients with AD performed significantly worse than control subjects on measures of sustained attention, divided attention, selective attention, and visual processing speed. The differences were not due to differences in age, education, or basic visual function. Strong relationships were identified between reduced attention skills and overall cognitive impairment. Conclusions: Deterioration of attention abilities occurs in early stages of AD, and likely contributes to functional decline in these patients. More routine assessment of visual attention deficits could give a more accurate measure of functionally useful perception in patients with AD who show normal visual acuity and visual fields, perhaps providing useful clues to diagnosis and staging.

Driver route-following and safety errors in early Alzheimer disease

Objective: To assess navigation and safety errors during a route-following task in drivers with Alzheimer disease (AD). Design/Methods: Thirty-two subjects with probable AD (by National Institute of Neurological and Communicative Disorders criteria) of mild severity and 136 neurologically normal older adults were tested on a battery of visual and cognitive tests of abilities that are critical to safe automobile driving. Each driver also performed a route-finding task administered on the road in an instrumented vehicle. Main outcome variables were number of 1) incorrect turns; 2) times lost; and 3) at-fault safety errors. Results: The drivers with mild AD made significantly more incorrect turns, got lost more often, and made more at-fault safety errors than control subjects, although their basic vehicular control abilities were normal. The navigational and safety errors were predicted using scores on standardized tests sensitive to visual and cognitive decline in early AD. Conclusions: Drivers with Alzheimer disease made more errors than neurologically normal drivers on a route-following task that placed demands on driver memory, attention, and perception. The demands of following route directions probably increased the cognitive load during driving, which might explain the higher number of safety errors.

Impaired Visual Search in Drivers with Parkinson's Disease

To assess the ability for visual search and recognition of roadside targets and safety errors during a landmark and traffic sign identification task in drivers with Parkinsons disease (PD).

Responding to requests from adult patients for neuroenhancements: Guidance of the Ethics, Law and Humanities Committee

In the last decade, persons who have no diagnosed medical or mental health condition are increasingly seeking and utilizing, for the ostensible purpose of enhancing their memory or cognitive skills, prescription drugs that were originally developed to improve executive function or memory in persons diagnosed with disorders such as attention deficit hyperactivity disorder or Alzheimer disease. Evidence suggests that this practice, now known as neuroenhancement, is gathering momentum. As a result, neurologists may be encountering patients without a diagnosed illness asking for medications with the goal of improving their memory, cognitive focus, or attention span. Strong arguments have been made for and against this practice, often reflecting strongly held convictions concerning the appropriate practice of medicine. The purpose of this report is to provide neurologists with an overview of the ethical, legal, and social issues surrounding the use of pharmaceuticals prescribed to enhance or augment normal cognitive or affective functioning, as well as practical guidance for responding to an adult patient’s request for neuroenhancement.

Driver landmark and traffic sign identification in early Alzheimer’s disease

Objective: To assess visual search and recognition of roadside targets and safety errors during a landmark and traffic sign identification task in drivers with Alzheimer’s disease. Methods: 33 drivers with probable Alzheimer’s disease of mild severity and 137 neurologically normal older adults underwent a battery of visual and cognitive tests and were asked to report detection of specific landmarks and traffic signs along a segment of an experimental drive. Results: The drivers with mild Alzheimer’s disease identified significantly fewer landmarks and traffic signs and made more at-fault safety errors during the task than control subjects. Roadside target identification performance and safety errors were predicted by scores on standardised tests of visual and cognitive function. Conclusions: Drivers with Alzheimer’s disease are impaired in a task of visual search and recognition of roadside targets; the demands of these targets on visual perception, attention, executive functions, and memory probably increase the cognitive load, worsening driving safety.