Olfactory dysfunction is common in traumatic brain injury because head impacts can shear off olfactory neurons.

“Now, speaking of brain injury, olfactory dysfunction is a common theme in traumatic brain injury for the following reason, these olfactory neurons as I mention extend wires into the mucosa of the nose, but they also extend a wire up into the skull. And they extend up into the skull through what's called the cribriform plate, it's like a Swiss cheese type plate where they're going through. And if you get a head hit, that bone, the cribriform plate, sheers those little wires off and those neurons die.”