In need of more thorough sterilisation? Getty

Surgical instruments may need to be cleaned more thoroughly after brain operations, following the news that they might be spreading proteins linked to Alzheimer’s disease.

There’s no evidence yet that spreading these proteins from one person to another can cause Alzheimer’s disease itself. But a study of eight people suggests that unclean instruments may sometimes lead to a rare and potentially fatal kind of brain bleeding disorder.

People who have Alzheimer’s disease typically have plaques of sticky amyloid proteins in their brains, although it remains unclear whether these are a cause or a consequence of the condition. But when amyloid builds up in blood vessels in the brain, it can sometimes make them so brittle that they leak or burst. This condition, called cerebral amyloid angiopathy (CAA), usually doesn’t develop until people reach their sixties or older.


But Sebastian Brandner, at University College London, and his team have been investigating the cases of eight people who developed CAA under the age of 60. Scouring their medical records, the team found that all eight of these people had undergone brain surgery during childhood or their teenage years for a variety of reasons.

Spreading proteins

Of the eight people, at least three have already died from strokes, which can be caused by CAA. They died between the ages of 37 and 57.

None of these people have known gene variants that would raise the risk of developing CAA early. Brandner’s team says the most likely explanation is that amyloid proteins were seeded into their bodies during childhood brain surgery, from instruments previously used for surgeries on people with Alzheimer’s disease. Creutzfeldt-Jakob Disease (CJD), a brain disease caused by prion proteins, is already known to have been spread in a similar way.

There has previously been evidence that Alzheimer’s proteins may have been spread to people in grafts of brain material, and injections of cadaver extracts used to boost growth – a procedure that was halted in the UK in 1985 when it was discovered that it carries a risk of spreading CJD. Last year, questions were raised over whether amyloid might also spread through blood transfusions.

But the new findings are the first to implicate surgical instruments as a means for transmitting amyloid.

Better sterilisation

Brandner’s team report that none of the eight people developed Alzheimer’s disease itself, or any other kind of dementia. However, this doesn’t rule out the possibility that amyloid spread through surgery could prime the brain for Alzheimer’s in later life.

Brandner says it may be wise to improve sterilisation procedures following brain surgery on adults, or introduce “single-use” instruments. Studies in animals have shown that amyloid proteins resist boiling, drying and exposure to formaldehyde.

But people who have had neurosurgery shouldn’t be too worried about developing amyloid-related diseases. It takes a long time for amyloid to build up in the body, so children would be most likely to be affected in this way within their lifetime. However, most children who need neurosurgery are operated on at children’s hospitals, where the instruments used are unlikely to have ever come into contact with an adult with Alzheimer’s disease.

“Any study that investigates potential links between contaminated neurosurgical instruments and the transmission of disease is to be welcomed, as the more we understand about eliminating risk, the greater the benefit for patients,” said a joint statement issued today by the Royal College of Surgeons and the Society of British Neurological Surgeons.

These organisations say that new guidance on sterilisation was issued in the UK in 2006 to prevent transmission of CJD, and that similar guidance could now be recommend to stop any spreading of amyloid.

Journal reference: Acta Neuropathologica, DOI: 10.1007/s00401-018-1822-2

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