1. Nervous System Sensitization

2. Peripheral Sensitization
Increased chemical and inflammatory response to tissue damage
Upregulation of existing peripheral receptors = mechanical and thermal hyperalgesia
Increased excitability and sensitivity of cell body in dorsal root ganglion, making them sense pain more easily
Collateral sprouting of new peripheral receptors
Smudging along spinal nerve root levels so that each nerve root now picks up information from a broader area, and they overlap more
More likely to have increased response to HEAT as well as mechanical inputs (movement, stretch, pressure)

3. Central Sensitization
Changes in dorsal horn of spinal cord
Increased excitability of dorsal horn neurons
Increased sensitivity for neuron’s chemical receptors (lower threshold for activation)
Sprouting of more receptors
Changes in motor and sensory cortex (smudging, disorganization)
Sympathetic nervous system on hyper-alert with increased perception of threat
Associated endocrine response – increased stress hormones
Associated immune response – pro-inflammatory

4. Central Sensitization: What it looks like
Nervous system wind-up
Pain persists, spreads, worsens, becomes less predictable
Smaller and smaller threshold for movement before pain
Pain linked more to thoughts and feelings
Pain linked to any perceived threat in life
Increased sensitivity for all senses (but not heat)
Allodynia: things that shouldn’t cause pain, do
Hyperalgesia: things that should just hurt a little, hurt a lot
The world/life gets progressively smaller and more exhausting

5. Motor Cortex and Sensory Cortex

6. Smudging

7. Smudging
For example, in chronic low back pain, there’s commonly a smudging in the motor cortex representing back muscles. This results in a loss of ability to differentially use and control key muscles that stabilize the spine, including multifidus and erector spinae muscles. Patients with chronic low back pain also commonly lose their ability to sense where their body is in space, and the sense of graphesthesia, or being able to determine words written on the body via the sense of touch

8. Graded Motor Imagery Left/Right Discrimination Motor Imagery
Mirror Therapy

9. Left/Right Discrimination

10. Motor Imagery

11. Mirror Therapy