Does nerve growth factor cause more pain in muscle or fascia?

Nerve growth factor (NGF) is known to greatly induce hyperalgesia (heightened sensitivity to pain).Researchers from Heidelberg University and Mannheim, Germany explored patterns of NGF sensitization in muscle and fascia of distal and paraspinal sites. The study was published in Muscle and Nerve Journal.

The researchers compared the effects of injecting nerve growth factor (an agent that causes sensitization to mechanical stimuli) to 8 subjects, to the tibialis anterior and erector spinae muscles and their fasciae.

The spatial extent of pressure sensitization, pressure pain threshold, and mechanical hyperalgesia was assessed at days 0.25, 1, 3, 7, 14, and 21. Chemical sensitization was also explored.

The results showed that the time-course and magnitude of nerve growth factor injection-induced sensitization to mechanical stimuli were generally similar across muscle and fascia. They were also mostly similar across two different muscle groups (the tibialis anterior and lumbar erectors). However, the spatial extent of mechanical sensitization in the tibialis anterior musculature was larger in the fascia than in the muscle and displayed a tendency to peak at 3 days post-injection. Pressure pain thresholds were lower, tonic pressure pain ratings, and citrate buffer evoked pain higher in fascia than in muscle.

The authors concluded that Spatial mechanical sensitization differs between muscle and fascia. Thoracolumbar fasciae appear more sensitive than tibial fasciae and may be major contributors to low back pain, but the temporal sensitization profile is similar between paraspinal and distal sites.