MYERS & COMPANY
Wiring, Plumbing and Insulation: the Different Types of Structures Injured Concussion (mTBI)
mTBI triggers multiple neurodegenerative cascades. They cut a wide swath and damage all sorts of different structures and systems.
Grey matter and white matter are both essential parts of the brain. About 40 percent is grey matter and 60 percent is white matter.
Grey matter and white matter are made up of different parts of brain cells called neurons.
Grey matter is made up of (and gets its coloration) from neuronal cell bodies and their dendrites. (The dendrites receive incoming signals.)
White matter is made up of axons, myelin and glial cells. It gets its coloration from the myeline sheaths. These structures comprise the transmission lines that carry messages between neurons and form the communication networks in the brain.
That’s a lot of terms. Here’s a image showing them and where they’re located:
Magnetic resonance imaging (MRI) scans can show damage to the white matter. The damages shows up in bright white on the scan. There are a bunch of different types of white matter injury.
When axons are injured, communication gets de-regulated and choppy. This is called: Diffuse Axonal Injury.
Axonal injury shows up on an MRI as a white matter hyper intensities (WMH).
But axonal injury isn’t the only condition that shows up as a WMH.
Across the whole population, the most frequent cause of WMH are microvascular ischemic changes. (Ischemia means that part of the body isn’t getting enough blood flow or oxygen.)
Microvascular ischemia can be caused by conditions like high blood pressure and diabetes—but it’s also caused by mTBI.
That makes sense. The mechanical forces of the collision and subsequent swelling can injure delicate blood vessels. And they’re also susceptible to the metabolic “cascade” that follows brain injury.
Another cause of these WMHs is “demyelination.” The myelin sheath has three functions:
Protects the axon (like insulation around a wire).
Allows signals to travel between neurons.
Maintains the strength of the signal (basically by re-charting it) as it travels down the axon.
When a myelin sheath is damaged—for example, in a mTBI—the electrical signal is slowed or stopped. Damage to the myelin sheath is what I referred to before as “demyelination.”
MRIs aren’t perfect. And different types show different things in the brain.
But If you have an MRI after an mTBI and it shows some bright white areas in the white matter it might make sense to get more specific imaging to determine whether the issue is being caused by your wiring (axons), plumbing (microvascular) or insulation (myelin).