Once again, scientists have raised the specter of Alzheimer’s as an infectious disease, theorizing it could be transmitted through some medical procedures and surgeries. Though this possibility is purely theoretical, the “circumstantial evidence for such transmission” is growing, say Swiss and Austrian researchers.

Their new study focuses on patients with Creutzfeldt-Jakob disease, who, many years before their deaths, had received surgical grafts of dura mater, the membrane that covers the brain and spinal cord. During autopsies, researchers discovered amyloid-β protein, the hallmark of Alzheimer’s disease, in the grey matter and blood vessels of their brains. Such results seemed unusual in patients so young — they were between the ages of 28 and 63 — especially since none had a family history of early-onset dementia.

For comparison purposes, then, the scientists performed another round of autopsies on 21 control patients who died of Creutzfeldt-Jakob disease at similar ages but had not received surgical grafts. However, none of these 21 comparison cases had the pathological signs associated with Alzheimer’s disease.

Based on this outcome, the researchers say it is “plausible” that the Alzheimer’s pathology may have resulted when small seeds of amyloid-β protein, a hypothesized trigger for dementia, were transferred from the grafts and transplanted in the patients' tissues. The grafts having been prepared from human cadavers provides added weight to this theory.

“Yet, alternative explanations are also possible,” wrote the team in their published paper. Despite this caveat, their research echoes a previous study published this past September.

Sterilized Surgical Instruments May Be Contaminated

In September, University College London scientists theorized that the signature Alzheimer’s proteins had spread via a hormone treatment prepared from cadavers based on their own autopsy results. Here, the British researchers conducted autopsies, including extensive brain tissue sampling, on eight patients with Creutzfeldt-Jakob disease.

While all the brains revealed the signature signs of Creutzfeldt-Jakob, six exhibited the amyloid-β pathology associated with Alzheimer’s as well. At death, these patients had been between the ages of 36 and 51. Once again, these patients were unusually young to display even the earliest signs of Alzheimer’s, yet none had a genetic history of early-onset Alzheimer’s.

One thing they did have, though, was a shared history of treatments with human growth hormone extracted from cadaver-sourced pituitary glands. The hormone treatments began in 1958 and ceased by 1985 following reports of Creutzfeldt-Jakob disease occurring among recipients — some of the treatments had been contaminated with prions, the infectious agent linked to that disease.

Analyzing the data, the British scientists hypotheisized Alzheimer’s may be transmissible in a manner similar to Creutzfeldt-Jakob disease. Potentially, the proteins found in the brains of Alzheimer’s patients could be spread to others by way of contaminated surgical instruments because the proteins are able to survive sterilization with formaldehyde.

Blood transfusions may also be a route of transmission, the scientists said, as is the case with Creutzfeldt-Jakob disease.

However, the scientists warn their findings are hypothetical. Strictly speaking, if transmission did occur, that only happened by way of the cadaver-derived human growth hormone injections, no longer in use. Cadaver-derived hormones and membranes have since been replaced with synthetic growth hormones and synthetic membranes.

Source: Frontzek K, Lutz MI, Aguzzi A, Kovacs GG, Budka H. Amyloid-β pathology and cerebral amyloid angiopathy are frequent in iatrogenic Creutzfeldt-Jakob disease after dural grafting. Swiss Medical Weekly. 2016.

Jaunmuktane Z, Mead S, Ellis M, et al. Evidence for human transmission of amyloid-β pathology and cerebral amyloid angiopathy. Nature. 2015.