HEALTHPLAN MAGAZINE

New research, published on October 11 in the journal Current Biology, suggests that encountering difficulties with navigation while walking could serve as an early warning sign of Alzheimer's disease. The study proposes that "impaired path integration," which pertains to one's understanding of distance and direction to perceive their location, may be an early indicator of Alzheimer's disease (AD).

Scientists explored the prospect of walking difficulties as an early symptom of Alzheimer's by utilising a virtual reality model that simulated the walking patterns of healthy elderly individuals. This virtual model was subsequently compared to data gathered from individuals afflicted with mild cognitive impairment (MCI).

The study included evaluations of both younger and older individuals without cognitive impairments, as well as older individuals suffering from mild cognitive impairment (MCI). A clear differentiation became evident: the key distinguishing factor lay in their capacity to perceive spatial orientation and accurately assess their location, with those having MCI showing notable deficits in this regard.

So, what exactly is path integration in spatial navigation?

Path integration entails the cognitive capacity to comprehend one's location within a space and determine how to navigate within it. Dr. John Dickson, a neurologist in the Memory Disorders Unit at the Department of Neurology at Massachusetts General Hospital, describes it as the cognitive ability to recognise one's position in space, as well as how they are moving (such as speed and direction). It also involves the calculations necessary for modifying movements in response to their current location and desired destination.

Crucially, parts of the brain associated with path integration are among the first to be affected by Alzheimer's, including the entorhinal cortex.

“This part of the brain contains special cells that are called ‘grid cells.’ Grid cells help people understand their position in space, similar to the way a grid can aid with localization in a two-dimensional plane. Grid cells can integrate information like location, distance, and direction.” explains Dr Dickson, adding that “Since the entorhinal cortex is affected early in Alzheimer’s disease, it is reasonable to assume the grid cells would also be affected, leading to impaired function regarding navigation.

In addition to the entorhinal cortex the parietal lobes are also affected in Alzheimer’s disease.”

The parietal lobes play a crucial role in visualising the spatial relationships among objects, and this capacity also has implications for navigation skills.

Dr. Andrew Newberg, a neuroscientist and director of research at the Marcus Institute of Integrative Health and a physician at Jefferson University Hospital, who was not involved in the study, pointed out that “One of the targeted brain regions in [Alzheimer’s] is the parietal lobe which is involved in spatial orientation of the body which probably interferes with knowing how a person is oriented.”

“Alzheimer’s also affects the temporal lobes which have structures involved in body sensation so if that is affected, you will have trouble turning and knowing where your body is,” he continued.

Dr. Dickson emphasised the need for further research to pinpoint precisely which regions of the brain are affected in the early stages.

“While the authors generally think the grid cells in the entorhinal cortex may be particularly involved in their findings, this study does not specifically demonstrate that changes in grid cells mediate the deficits noted,” the neurologist said.

“The authors note that further research is needed to determine the exact changes in the brain that cause the deficits in path integration they see in this study.”

What are the early signs of Alzheimer's?

Short-term memory loss stands out as the most common initial symptom of the disease. Other early indicators may encompass losing track of dates or location, difficulty finding words, trouble with complex task planning and problem-solving, as well as changes in mood or personality. It's important to note that these symptoms may occasionally overlap with typical age-related cognitive changes in the earliest stages, making it challenging to distinguish between normal ageing and Alzheimer's. If individuals experience cognitive changes that concern them, it's advisable to discuss these with their doctor to ascertain whether further evaluation is warranted.

According to Dr. Arman Fesharaki-Zadeh, an assistant professor of psychiatry and neurology, and the medical director of dementia and behavioural neurology at Yale School of Medicine, “The family members and loved ones of AD patients would often express concern about patient’s increasing difficulties to smoothly navigate in familiar locations, manifested as episodes of disorientation and even getting lost in familiar locations.

“Episodic memory deficits could be described as difficulties with recall of recent conversations or events and asking the same question about the content of a recent discussion repeatedly.”

Diagnosing Alzheimer's in Its Early Stages

For those wondering about the diagnosis of early-stage Alzheimer's, modern healthcare experts have developed more precise diagnostic methods. The detection of amyloid and phosphorylated Tau in cerebrospinal fluid (CSF) now permits the confirmation of AD diagnoses, even in the early stages, with high accuracy.

“Alzheimer’s disease biomarkers of amyloid-beta and/or tau are growing in their use and importance in the clinical diagnosis of patients in the early stages of Alzheimer’s disease,” Dr Dickson noted.

Biomarker tests entail a lumbar puncture to collect CSF for measuring amyloid-beta and tau levels. Imaging-based techniques involving positron emission tomography (PET) also assess amyloid-beta or tau levels in the brain, and they have received FDA approval. Unfortunately, insurance coverage for these tests remains limited for most people but is progressively utilised in research studies. The Centers for Medicare and Medicaid Services (CMS) has proposed extending coverage for amyloid PET scans, which could increase their clinical use if finalised.

Additionally, blood-based biomarkers for amyloid-beta and tau have been developed, although they are not yet widely used in clinical settings. However, they may become a convenient means of obtaining biomarker information via a simple blood test. In addition to these biomarkers, Alzheimer's disease diagnostic evaluations include an in-depth medical history and examination, cognitive assessments, and brain magnetic resonance imaging (MRI) Dr Dickson added

Talking to your doctor

If you're concerned about Alzheimer's, discussing cognitive symptoms with your doctor is crucial to determine whether further evaluation is necessary.

One current point of interest in Alzheimer's research is anti-amyloid therapy, a new class of medications designed to eliminate amyloid-beta from the brain.

While there is no cure for the disease, new drugs have emerged to help delay its symptoms. For instance, lecanemab received full FDA approval earlier in 2023. However, it's important to note that this medication comes with potential serious side effects, such as brain swelling or bleeding, so its use should be carefully considered.

“Patients should discuss with their doctors right away if they have noticed changes in their thinking and memory. Alzheimer’s disease is not the only cause of changes in memory and thinking and your doctor should order blood work and brain imaging to rule out alternative causes,” said Dr. Vives-Rodriguez.

Furthermore, tests that assess thinking and memory are essential for detecting subtle cognitive changes that may exceed typical age-related expectations. If further concerns persist, a neuropsychologist may conduct formal neuropsychological testing.

Finally, if concerns persist, consulting with a neurologist is advisable for a comprehensive evaluation to assess the possibility of Alzheimer's disease or other neurological disorders presenting with cognitive changes. A neurologist can guide patients toward advanced testing that can assist in early Alzheimer's disease diagnosis and treatment.

In summary, research highlights the potential connection between difficulty with navigation during movement and early indications of Alzheimer's disease. Alongside navigation issues, early signs of AD encompass short-term memory loss, word-finding difficulties, trouble with complex task planning and problem-solving, and mood or personality changes.

Alzheimer's disease biomarkers have gained importance in diagnosing early-stage patients, with CSF-based and imaging-based approaches becoming pivotal tools. The inclusion of blood-based biomarkers may further enhance early diagnosis in the future.

It is essential to discuss cognitive symptoms with your doctor if you have concerns about Alzheimer's disease. Consideration of anti-amyloid therapy should also be weighed carefully.

While there is no cure, there are medications available to help delay symptoms. If cognitive changes persist, consulting with a neurologist is recommended for advanced testing and assessment.

Source: HealthLine