Resources > What a Diagnostic Nerve Block Can Tell Us About Your Spasticity
What a Diagnostic Nerve Block Can Tell Us About Your Spasticity
A diagnostic nerve block (DNB) is a low-risk, in-clinic procedure that helps us better understand what’s causing your muscle tightness. It answers two key questions:
- Is the tightness mainly from nerve overactivity, or are the muscles and joints themselves stiff or shortened?
- How likely is it that treatments like botulinum toxin or phenol injections will help?
How the Test Works
Imagine your nerves as branches of a tree and your muscles as leaves. If we temporarily numb one branch, we can see which leaves respond. A diagnostic nerve block works the same way: we “pause” the activity of a specific nerve to see how the muscles connected to it behave.
This is done by injecting a small amount of local anesthetic, similar to what a dentist uses, around a motor nerve.
What the Results Tell Us
If the spastic muscle becomes easier to stretch or move, that tells us nerve overactivity is the main cause—and treatments like botulinum toxin or phenol are more likely to help.
If there’s little or no change, the issue may be a fixed contracture, tendon shortening, or joint stiffness. In those cases, we might recommend stretching, bracing, therapy, or a surgical consultation instead.
We typically use ultrasound and/or electrical stimulation to guide the injection. Ultrasound helps us see the nerve directly, and electrical stimulation confirms we’re in the right spot by producing a small, temporary muscle twitch.
Why This Matters
Diagnostic nerve blocks are especially useful when we’re unsure what’s driving the spasticity. They help us:
- Set realistic treatment expectations with you and your caregivers
- Avoid unnecessary injections when tightness isn’t nerve-driven
- Tailor treatment plans when multiple muscles are involved
- Refine your goals, especially when standard treatments haven’t helped
For example, if your goal is to open your hand more easily, but a nerve block doesn’t make any difference, we might shift focus toward assistive devices or surgical options rather than continuing with repeated injections.
What to Expect
- The entire procedure takes less than 20 minutes and is done right in the clinic.
- You may feel temporary numbness or weakness in the area for a few hours.
- There’s minimal downtime, and we’ll usually ask you to try a few movements before and after the injection to compare.
Key Takeaways
- A diagnostic nerve block helps us understand whether tightness is due to spasticity or contracture.
- It guides decisions about botulinum toxin, phenol, stretching, or surgery.
- It supports clearer communication, more targeted treatment, and better goal-setting.
Final Thoughts
We don’t use diagnostic nerve blocks for everyone but when there’s uncertainty about what’s really causing your symptoms, they’re one of the most valuable tools we have to personalize your care and improve your outcomes.