Posterior cortical atrophy syndrome

MONDAY, Dec. 23, 2024 -- Humans aren’t the only ones who lose a step or two brain-wise as they age. Artificial intelligence (AI) programs start to show signs of mild cognitive impairment as they grow older, a new study published Dec. 20 in the journal the BMJ says. Older versions of chatbots, like older patients, tend to perform worse on tests of cognitive ability. “Not only are neurologists unlikely to be replaced by large language models any time soon, but our findings suggest that they may soon find themselves treating new, virtual patients -- artificial intelligence models presenting with cognitive impairment,” wrote a research team led by Dr. Roy Dayan , a neurologist with Hebrew University in Jerusalem. For this study, researchers assessed the cognitive abilities of the leading publicly available AI programs, which are also called “large language models [LLMs].” AI is being tested for its ability to help in medical treatment, but “if we are to rely on LLMs for medical diagnosis and care, we must examine their susceptibility to human impairments such as cognitive decline,” researchers wrote in a journal news release. The AI programs responded to questions from the Montreal Cognitive Assessment (MoCA) test, a standard test used to check for signs of brain aging and early dementia in seniors. The maximum score on the test is 30 points, with a score of 26 or above generally considered normal, researchers said. ChatGPT 4o had the highest score on the test, at 26 out of 30, results show. ChatGPT and Claude 3.5 “Sonnet” both scored 25, and Gemini 1.0 scored only 16. “None of the large language models ‘aced’ the MoCA test, in the parlance of one American president,” researchers wrote. All the AI programs performed poorly at visuospatial skills and organizational tasks, like connecting numbers and letters in an ascending order. “The chatbots seem to have difficulty in tasks that demand both visual executive function and abstract reasoning, as opposed to tasks requiring textual analysis and abstract reasoning, such as the similarity test, which were performed flawlessly,” researchers wrote. In fact, this pattern of impairment resembled human patients with posterior cortical atrophy, a variant of Alzheimer’s disease , researchers said. “Moreover, as in humans, age is a key determinant of cognitive decline: ‘older’ chatbots, like older patients, tend to perform worse on the MoCA test,” the researchers added. For example, the Gemini 1.0 and Gemini 1.5 AI models differed by six points in test results. “As the two versions of Gemini are less than a year apart in ‘age,’ this may indicate rapidly progressing dementia,” researchers wrote. These flaws underscore the uphill battle AI will face in replacing human doctors. Or, to put it more mildly -- “These findings challenge the assumption that artificial intelligence will soon replace human doctors,” the research team concluded. Whatever your topic of interest, subscribe to our newsletters to get the best of Drugs.com in your inbox.

WEDNESDAY, Jan. 24, 2024 -- Strange visual disturbances occur early in about 10% of Alzheimer's cases, and when this happens it almost always signals the impending arrival of the disease, a new study finds. The condition is called posterior cortical atrophy (PCA). It involves a sudden difficulty in performing vision-related tasks -- for example writing, judging whether an object is moving or stationary, or easily picking up a dropped item. Everyday tasks like these become difficult despite the fact that a person's eye exam comes out fine. “We need more awareness of PCA, so that it can be flagged by clinicians,” said study co-lead author Marianne Chapleau , of the University of California, San Francisco's department of neurology. “Most patients see their optometrist when they start experiencing visual symptoms and may be referred to an ophthalmologist who may also fail to recognize PCA,” she said in a UCSF news release. “We need better tools in clinical settings to identify these patients early on and get them treatment.” To determine just how predictive of dementia PCA might be, Chapleau's team analyzed data on over 1,000 patients at 36 sites in 16 countries. PCA tended to emerge at a fairly young age -- 59, on average. Patients with PCA often failed to accurately copy simple diagrams, had trouble gauging an object's location or had difficulty visually perceiving more than one object at a time, the research showed. Math and reading skills also began to falter. In 94% of cases, people experiencing PCA went on to develop Alzheimer's disease , the UCSF team found. The remaining 6% developed other dementias such as Lewy body disease or frontotemporal lobar degeneration. The researchers pointed out that's far more predictive of dementia than a condition such as memory loss: Only 70% of people with failing memories go on to develop dementia, they said. Many people may show no cognitive issues when first stricken with PCA, but the study found that by about four years later, mild or moderate deficits in memory, executive function, behavior, and speech and language became apparent. The findings were published Jan. 22 in The Lancet Neurology journal. Renaud La Joie , also from UCSF's department of neurology and the university's Memory and Aging Center, is first author of the study. He believes that because PCA typically emerges years before actual dementia, it could point to patients who might be helped by newly approved Alzheimer's medications. Some of those medications target tau, a protein that builds up in the brains of people with Alzheimer's disease. “Patients with PCA have more tau pathology in the posterior parts of the brain, involved in the processing of visuospatial information, compared to those with other presentations of Alzheimer’s. This might make them better suited to anti-tau therapies,” he explained. “It’s critical that doctors learn to recognize the syndrome so patients can receive the correct diagnosis, counseling and care," added senior study author Dr. Gil Rabinovici , who directs the UCSF Alzheimer’s Disease Research Center. “From a scientific point of view, we really need to understand why Alzheimer’s is specifically targeting visual rather than memory areas of the brain," he added. "Our study found that 60% of patients with PCA were women -- [getting a] better understanding of why they appear to be more susceptible is one important area of future research.” Sources University of California, San Francisco, news release, Jan. 22, 2024 Disclaimer: Statistical data in medical articles provide general trends and do not pertain to individuals. Individual factors can vary greatly. Always seek personalized medical advice for individual healthcare decisions. Posted January 2024 More news resources FDA Medwatch Drug Alerts Daily MedNews News for Health Professionals New Drug Approvals New Drug Applications Drug Shortages Clinical Trial Results Generic Drug Approvals Subscribe to our newsletter Whatever your topic of interest, subscribe to our newsletters to get the best of Drugs.com in your inbox.

A team of international researchers has completed the first large-scale study of posterior cortical atrophy, a baffling constellation of visuospatial symptoms that present as the first symptoms of Alzheimer's disease. These symptoms occur in up to 10% of cases of Alzheimer's disease. A team of international researchers, led by UC San Francisco, has completed the first large-scale study of posterior cortical atrophy, a baffling constellation of visuospatial symptoms that present as the first symptoms of Alzheimer's disease. These symptoms occur in up to 10% of cases of Alzheimer's disease. The study includes data from more than 1,000 patients at 36 sites in 16 countries. It publishes in the Lancet Neurology on Jan. 22, 2024. Posterior cortical atrophy (PCA) overwhelmingly predicts Alzheimer's, the researchers found. Some 94% of the PCA patients had Alzheimer's pathology and the remaining 6% had conditions like Lewy body disease and frontotemporal lobar degeneration. In contrast, other studies show that 70% of patients with memory loss have Alzheimer's pathology. Unlike memory issues, patients with PCA struggle with judging distances, distinguishing between moving and stationary objects and completing tasks like writing and retrieving a dropped item despite a normal eye exam, said co-first author Marianne Chapleau, Ph.D., of the UCSF Department of Neurology, the Memory and Aging Center and the Weill Institute for Neurosciences. Most patients with PCA have normal cognition early on, but by the time of their first diagnostic visit, an average 3.8 years after symptom onset, mild or moderate dementia was apparent with deficits identified in memory, executive function, behavior, and speech and language, according to the researchers' findings. At the time of diagnosis, 61% demonstrated "constructional dyspraxia," an inability to copy or construct basic diagrams or figures; 49% had "space perception deficit," difficulties identifying the location of something they saw; and 48% had "simultanagnosia," an inability to visually perceive more than one object at a time. Additionally, 47% faced new challenges with basic math calculations and 43% with reading. We need better tools and training to identify patients "We need more awareness of PCA so that it can be flagged by clinicians," said Chapleau. "Most patients see their optometrist when they start experiencing visual symptoms and may be referred to an ophthalmologist who may also fail to recognize PCA," she said. "We need better tools in clinical settings to identify these patients early on and get them treatment." The average age of symptom onset of PCA is 59, several years younger than that of typical Alzheimer's. This is another reason why patients with PCA are less likely to be diagnosed, Chapleau added. Early identification of PCA may have important implications for Alzheimer's treatment, said co-first author Renaud La Joie, Ph.D., also of the UCSF Department of Neurology and the Memory and Aging Center. In the study, levels of amyloid and tau, identified in cerebrospinal fluid and imaging, as well as autopsy data, matched those found in typical Alzheimer's cases. As a result, patients with PCA may be candidates for anti-amyloid therapies, like lecanemab (Leqembi), approved by the U.S Food and Drug Administration in January 2023, and anti-tau therapies, currently in clinical trials, both of which are believed to be more effective in the earliest phases of the disease, he said. "Patients with PCA have more tau pathology in the posterior parts of the brain, involved in the processing of visuospatial information, compared to those with other presentations of Alzheimer's. This might make them better suited to anti-tau therapies," he said. Patients have mostly been excluded from trials, since they are "usually aimed at patients with amnestic Alzheimer's with low scores on memory tests," La Joie added. "However, at UCSF we are considering treatments for patients with PCA and other non-amnestic variants." Better understanding of PCA is "crucial for advancing both patient care and for understanding the processes that drive Alzheimer's disease," said senior author Gil Rabinovici, M.D., director of the UCSF Alzheimer's Disease Research Center. "It's critical that doctors learn to recognize the syndrome so patients can receive the correct diagnosis, counseling and care. "From a scientific point of view, we really need to understand why Alzheimer's is specifically targeting visual rather than memory areas of the brain. Our study found that 60% of patients with PCA were women -- better understanding of why they appear to be more susceptible is one important area of future research."