As you know, nerves are the slowest healing structures of the human body.  This can make time really slow down for patients who have had nerve injuries!  Functional recovery can take weeks to months. It can be frustrating for the patientfor obvious reasons, but also the clinician as I tend to get the same question day in and day out, “is my nerve healing and how much longer?”.  Now everyone is different, but I have posted several pictures of examination procedures I proceed with and rationale in order to better answer this question for us, but also the patient.

To get a better background that is beyond the content of this post, check out nerve injury definitions here.

General rule is that nerves re-grow at about 1 mm a day, which is about the depth of a dime, or simply one inch a month.  Some literature say 0.5mm to 9mm but I typically go with 1mm in clinical practice. This depends obviously on age, amount of time the nerve was compressed prior to decompression (either surgically –which can hamper growth–or through physical therapy), comorbidities, site of lesion, etc.  You can also read more about “Rule if 18” here but typically used for peripheral nerves.

So in case a patient arrives to your clinic after surgery to decompress the L5 nerve root,  the following is examples of examination assuming a positive response to surgery and nerve has started to regrow:

Reflex hammers do not get used in physical therapy practice as much as I would like to see!  Bring them out!  Not a huge reliability source but does add significant value (in my opinion) to the neurological exam.

L4 Reflex
S1 Reflex

Motor Function

Manual muscle testing again does not give very reliable data but can be of significant benefit in this case.  We all can pick up differences with experience, and I feel performing MMT on the following muscle groups is the most reliable (more difficult to determine important differences in more proximal muscles in my opinion, as well as pain from low back can hinder results).  Don’t press down for 1-2 seconds, but perform a short-duration testing of at least 5 seconds to actually pick up differences.

Anterior Tibialis--L4
Extensor Hallucis Longus--L5

Sensory Disturbance

I find that motor regeneration occurs prior to sensory.  However, the sensory disturbances can be usually what you hear most from the patient (meaning, still having numbness in a particular area, etc).  The symptoms can be allodynic to mild palpation.  I do not have any hard evidence on measuring the sensory disturbance from most proximal region using monofilament (or you can also use two-point discrimination) and tape measure (such as starting from bony prominence as fibular head) but find it can be useful.

Testing sensory disturbance change using monofilament and tape measure

Functional recovery following nerve injury can be very difficult to measure.  I use these neurological tools as appropriate to help with determining nerve growth.  What are your thoughts?  Any comments on what you use to educate patients about this slow process?  Any other measuring guides available (other than EMG/NCV)?




    1. Good point Dr. E. Definitely need to differentiate between all 3, physiologically weak, neurologically weak or just simply inhibited. Will certainly make a difference in overall outcome of assessment but lead to treatment.

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