Introduction to Parkinson's Science/Q Page 90

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What is the Braak model?
It would be easier to address the issue of spreading if we knew exactly what the infective agent was! Reading most literature on the subject you might get the impression that the disease is all about a part of the brain called the sbstantia nigra, but, whatever the agency is that is at work, it leaves its footprints all over the place. These take the form of dead and dying neurons containing clumps of a protein called alpha synuclein, better known as Lewy bodies and neurites.

Professor Heiko Braak works at the Institute of Clinical Neuroanatomy, Johann Wolfgang Goethe-Universit, Frankfurt am Main, and he had the idea of following the trail of footprints back to its source.

He published the results in 2003/4 and and divided the pathway into a number of sequential stages:-

This, coupled with the observation that one of the earliest symptoms of the disease is a reduction in the sense of smell, would appear to imply that the infective agency is inhaled.

Hawkes et al (1997) studied this aspect of the disease and concluded:-

"Olfactory damage in Parkinson's disease is consistent and severe and may provide an important clue to the aetiology of the disease. "