In this 2018 paper, Zorec & Verkhratsky discusses the brain biology and processes leading to neurodegenerative illness, such as Alzheimer’s, Parkinson’s and various forms of sclerosis (ALS/MS). 

WHIPCON finds the paper interesting because several scientific studies points towards repeated concussions / mTBI / traumatic brain injury as a leading cause of memory and learning problems, also called cognitive decline (ref) (ref) (ref), (ref), to Parkinson’s’  (ref) and to Alzheimer’s (ref) (ref).

What brain condition precedes Alzheimer’s, Parkinson’s and other neurodegenerative diseases?

In a normal functioning brain we see a type of ‘glue’ cells, called astrocytes residing between nerve cells. Their job is to clean the brain and retain the balances in the brains inner environment, and they have multiple other functions as well. See the star like shape of the astrocytes in the illustration.

In order to do their work properly the astrocytes need to be fed with a substance called noradrenaline, or NA**, which is produced in the brain stem, in a small gland called locus coeruleus (LC). Additionally NA is released throughout the brain in the endings (NA-projections) of specific nerves that links to the LC gland in the brain stem. This is illustrated with red arrows in the figure.

If there is not enough NA around for the astrocytes to function normally and keep the fine balances in the brain and spinal environment – processes leading to neurodegenerative illness will be the result (with building up tau-protein deposits in the brain). Therefore, possible methods to assure sufficient NA supply discussed.

NA drop can happen at insufficient blood supply to the LC gland, which is illustrated as narrow egg (white with red edge) in the brain stem. Illustration reproduced with Prof. Verkhratsky’ s kind acceptance.

Verkhratsky

WHIPCON finds it highly likely that the impaired blood supply to the brainstem happens after a combined mild traumatic brain and neck injury, because:

  • In a personal correspondence with Professor Francis Smith (the famous radiologist, who held the key speech at the 100 years anniversary of the American Radiology Association), Prof. Smith explain why neck injury (such as whiplash) could be the cause of the impaired vascularization in the brain stem, as presented in an upright fMRI scan. This and similar findings (ref) could be key in explaining why a combined mild traumatic brain- and neck injury could lead neurodegenerative illness. After all, people frequently hit their head and neck at the same time, especially women, whose neck is not as strong as that of men. 
  • After an initial rise in NA after a mild traumatic brain injury (concussion) (ref), likely representing an increased “demand for cleaning”, over time the turnover of NA drops to an abnormally low level.

Related Reading

Injury cascades in TBI-related neurodegeneration (ref).

Explanatory

*Astrocytes are the cells that clean up the brain while we sleep. Astrocytes balance a number of conditions in the brain and of the rest of the central nerve system. They are involved in blood supply. Their supportive functions include neurotransmitter clearance, ion buffering, metabolite delivery, the immune system. 

**NA is called norepinephrine in USA, noradrenaline in Europe). NA is a neurotransmitter; i.e. a chemical that chemically can send nerve signals from one nerve to another, in the gaps where neurons meet (called synapsis).