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Remembering and forgetting.

Risky surgeries.

Text: Sabine Goldhahn

Surgical interventions alleviate suffering and can save lives. For older patients in particular, however, operations are sometimes followed by memory problems. A research group at the University of Basel is studying this phenomenon in the hope of finding ways to keep the symptoms at bay.

No surgical procedure is entirely risk-free. When a patient appears confused in the wake of an operation, or reports significant memory loss perhaps even weeks later, researchers and clinicians call this a perioperative neurocognitive disorder. But is it a reason to forgo surgery? The following answers to key questions help shed light on the dilemma.

Are memory problems following surgery a cause for concern?

Yes. If memory problems occur in the wake of surgery, this is considered a complication: in this case, an impairment of brain function. The phenomenon is also known as “postoperative cognitive dysfunction”, or POCD. It is distinct from post- operative delirium, another brain disorder that can also occur after surgical procedures. Severe cases of postoperative delirium can result in lasting disorientation, loss of independence, or even increased mortality.

What form do these memory problems take and when do they occur?

The symptoms of POCD resemble a mild form of Alzheimer’s disease, and generally occur within a few weeks to months after surgery. Affected patients are forgetful and struggle to learn new things. Relatives occasionally report that they are no longer themselves. Symptoms can be very subtle, and often go unnoticed by those affected.

How is a case of POCD identified?

There is a high number of undiagnosed cases. Even for medical experts, it can be difficult to recognize POCD and distinguish it from age-related memory loss. Special memory tests, some of which are used in Alzheimer’s, are required for diagnosis. For the diagnosis to be accurate, the first test must be carried out before the operation. This provides a benchmark that specialists can subsequently use to determine whether the patient’s memory has deteriorated.

Are POCD assessments performed routinely?

No, in routine practice, this is often not possible yet. At the moment, POCD-related diagnostics are almost exclusively limited to research projects, for instance at University Hospital Basel. Here and at the Memory Clinic at the Felix Platter Hospital, researchers from the University of Basel developed the CogCheck tablet app, specifically to allow faster testing of their patients. The app includes key neurocognitive tests that patients can complete without external assistance, for example before undergoing a surgical procedure. The results are compared against data from a large number of healthy subjects of the same age and gender, and a similar level of education. If an individual’s test results show a significant deviation from the norm, this suggests an existing cognitive impairment.

How frequent is POCD and who is most likely to be affected?

There are few exact figures. What we do know is that POCD is particularly common among older people – above the age of 60, the likelihood is around 40 percent – or patients already suffering from dementia or impaired memory function before the intervention. It is much rarer for younger people to develop POCD.

Are there any particular risk factors?

Aside from age or pre-existing memory problems, the primary factors are the extent and type of the operation. For instance, delirium and POCD are particularly common following open-heart surgery. However, it has also been observed in the wake of hip operations or other major surgery. As far as we know, neither the anesthetic drugs used nor the type of anesthesia affect the likelihood of POCD.

What are the possible causes?

Any operation puts strain on the body, eliciting a stress reaction by the immune system. This triggers inflammatory processes that can directly influence neurons. That said, the exact mechanism behind perioperative neurocognitive disorders is not yet known. In all likelihood, there are a number of factors that contribute to the occurrence of POCD.

How is POCD treated?

POCD symptoms generally disappear after around a year. Until that happens, there is no specific treatment, such as medication. Nonetheless, patients are encouraged to stay physically and mentally active. This could involve anything from social contact, sports, and games to train the memory.

How great is the risk of not regaining full cognitive function?

There are no exact figures on this, but it is relatively rare. If symptoms persist for longer than a year, it is likely that the patient was already suffering from some form of memory problem, but it was slight enough to go unnoticed until the operation. An increasing number of anesthesiologists and surgeons are careful to tell their high-risk patients that surgery may unmask mild forms of dementia.

Are there precautions that can be taken against POCD?

Given the different risk factors at play, there is currently no sure-fi re way to prevent POCD. There is no proven prophylactic drug at present. That said, everyone can take steps to minimize the potential negative effects of surgery. This could involve dedicated exercises to boost physical fitness and memory for several months leading up to the procedure. The positive effects of this kind of “prehab” are known from cancer treatment. A targeted prevention strategy for perioperative neurocognitive disorders has considerable prospects of success.

Clinical Study

Anesthesiologists Nicolai Göttel and Luzius Steiner are currently conducting a clinical study at the University of Basel in the hope of identifying a structural biomarker for postoperative cognitive dysfunction. The underlying idea: Alzheimer’s disease causes the hippocampus – the region of the brain where memories are formed – to shrink. The researchers’ assumption is that POCD is also accompanied by shrinkage of the hippocampus. They hope to use magnetic resonance imaging (MRI) to document this reduction in brain volume and compare it against the results of memory tests conducted on both surgical patients and healthy test subjects. The aim of the study is to expand knowledge regarding POCD with a view to developing both treatment strategies and prophylactic measures.

More articles in the current issue of  UNI NOVA.

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