Parkinson’s disease could be much more complex than what has been believed up till now and, in particular, various sub-types of the disease could exist. If this were the case, all patients would have to be assessed individually, and each one would need customized treatment.

Taking stock of the situation regarding this illness, which is still to a certain extent mysterious and “controversial”, is a review of the available studies published in the Journal of Parkinson’s Disease by Per Borghammer and Nathalie Van Den Berge, two researchers from the University of Aarhus, Denmark. The researchers thoroughly examined the most recent data, obtained by a number of international teams through imaging studies (MRIs and other examinations), as well as through assessments of tissue samples, taken from the brains of humans and animals suffering from the disease.

In recent years – write the Danish researchers – there is an increasingly popular hypothesis that Parkinson’s disease may originate from aggregations of an altered form of the alpha-synuclein protein (a very important protein for the body). These aggregations are not formed in the brain, as was always thought, but in the enteric nervous system (and from there they are transported via the vagus nerve and are accumulated in the brain, destroying dopaminergic cells). However, according to various observations made, especially in autopsies, this is not the case for all sufferers. Therefore, it is possible that there are at least two large families of this disease: the form of Parkinson’s disease that actually does have its origins in the innervation of the intestine (called gut-first) and hence initially causing damage to the peripheral nervous system; and a second “family”, defined as brain-first, in which Parkinson’s originates in the brain and is then passed on to the nerve fibres of the intestine and other peripheral areas.

If this dual-hit hypothesis is confirmed, it will become easier to find the right diagnosis and therapy for different types of patients. And not only this. Research could be more “targeted”, in an attempt to understand what triggers the disease initially at peripheral level (other than the intestine, the olfactory bulb also seems to be a possible cause of the initial damage) or, on the contrary, at central level, and to define specific treatment programmes to slow down its development. For example, in the case of the gut-first form of the disease, ad hoc anti-inflammatories could be studied, but also therapies like faecal microbiota transplants or special probiotics.

According to the latest estimates, Parkinson’s disease (which is the second most common age-related neuro-degenerative disease after Alzheimer’s) affects 3% of over 65 year-olds and up to 5% of people over 85.