Risk of cognitive decline following epilepsy surgery

In severe epilepsies, surgical intervention is often the only remedy — usually with great success. But while neuropsychological performance can recover in the long term after successful surgery, on rare occasions, unexpected declines in cognitive performance occur. Researchers at the University of Bonn have now been able to show which patients are at particularly high risk for this.

An epilepsy disorder cannot always be controlled with medication. In such cases, sufferers should seek advice as to whether surgery is an option. During the procedure, surgeons selectively remove damaged brain tissue from which seizures originate. This often provides a complete cure for the patients.

“Surgery has revolutionised the treatment of severe epilepsies,” said Dr Juri-Alexander Witt, a neuropsychologist at the University Hospital Bonn. “However, with epilepsy surgery, there is always a risk of cognitive decline. That said, long-term studies have shown that brain performance can recover in the long term after successful surgery.”

However, in a small proportion of sufferers, unexpected drops in performance do not occur until months or years after the surgery. Researchers in Professor Albert Becker’s group at the University of Bonn wanted to know the reason behind this and so drew on the University Hospital Bonn’s extensive experience in epilepsy surgery, gaining access to brain tissue samples that had in some cases been taken decades ago.

“We analysed a total of 24 samples from men and women who had been diagnosed with serious cognitive decline months or even years after surgery,” Reimers said. In the course of this, the researchers came across a striking finding: in those affected, the removed tissue was damaged by secondary disease at the time of surgery — either through inflammation or incipient Alzheimer’s dementia.

“With these pre-existing conditions, the body’s defences are particularly active,” Becker said. “It’s possible that the trauma of the surgical procedure further stimulates the immune system in the brain to attack healthy brain tissue.”

With their work now published in the Annals of Neurology, the researchers plan to study samples from other epilepsy centres to corroborate their finding. The results may help identify affected individuals for whom surgery should be avoided, with Witt noting, “We currently have various diagnostic methods at hand that we can use for this purpose.”

For instance, all patients complete an extensive battery of psychometric tests prior to surgery to determine their cognitive performance. When considered together with brain scanner images and the examination of cerebrospinal fluid by means of a lumbar puncture, some of the results already allow conclusions to be drawn about concomitant diseases.

“If such tests indicate inflammation or the onset of neurodegenerative disease, entirely new treatment options emerge, such as anti-inflammatory pharmaceuticals, which may make surgery unnecessary,” Becker said.

Image caption: Looking at a neuropathological large slice preparation — Prof Dr Albert Becker, Dr Juri-Alexander Witt and Annika Reimers at the University Hospital Bonn. Image ©Barbara Frommann/University of Bonn.

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