Abstract of The Week: Negative Neurodynamic Tests Do Not Exclude Neural Dysfunction in Patients With Entrapment Neuropathies by Larissa T. Baselgia, MSca, David L. Bennett, PhDb, Robert M. Silbiger, MScc, and Annina B. Schmid, PhDb.
We chose this abstract to highlight this week because ULTT are commonplace in clinical practice. As with all tests, sound clinical reasoning is imperative and each test requires a sound clinical perspective. In this case the researchers propose that a negative neural dynamic testing with CTS may indicate small fiber involvement. Also, that 54% of patients who have positive EMG testing for CTS will have negative upper limb tension tests biasing the median nerve. It is also interesting to note that the researches did both the median nerve biases in this study (you will have to read the study to see the breakdown of these specific tests).
At IFOMPT 2016 in Glasgow, Dr. Schmid (co-author of this paper) provided an excellent lecture addressing nerve entrapment and posed the following questions:
What if a patient presents with numbness in the hand and appears to have nerve entrapment but, …
- Neurological tests are negative?
- Neurodynamic tests are negative?
- Symptoms are extraterritorial?
For those of us who commonly utilize a scanning examination and perform ULTT these clinical conundrums occur frequently. The answer appears to lie in two important anatomical facts.
Firstly, the composition of a peripheral nerve. A typical peripheral nerve is comprised of small and large fibers (and may subsets of these fibers for detection of vibration, heat, pain, etc.). The small fibers (unmyelinated C fibers and thinly myelinated A delta fibers) comprise of 80% of the conductive tissue and the large fibers care the remaining 20%. EMG testing only can confirm large fiber compromise, and qualitative sensory testing (QST) has to be performed to further assess sensory deficits. In this study, the subjects with positive ULTT had increased thermal and mechanical detection thresholds and those with negative had decreased thermal detection. So, thermal was the only dominant positive and negative with thermal detection. Therefore, the authors concluded that in this study, 54% of the time, a positive EMG study, with negative ULTT indicates both large and small fiber compromise.
Secondly, the small fibers (A delta) of the peripheral nerve innervate the epineurium. One of the features of neurodynamic testing is mechanosensitivty, theorized to come from these fibers. If they are compromised, a pain response may not be possible. Therefore, it may be possible that a negative ULTT in the presence of other factors indicating nerve entrapment may indicate a positive for small fiber compromise.
In conclusion, the next time you have a patient who presents with signs and symptoms of nerve entrapment, do not relay on the one tests (EMG, ULTT, reflex Testing, sensation, etc.), but do a thorough assessment using keen clinical reasoning considering both the complex anatomy and physiology of the peripheral nerve. The patient with CTS signs and symptoms who presents with a negative ULTT may have significant nerve compromise, which may be confirmed with EMG testing. But, if they have negative ULTT and negative EMG testing, it is possible that the small fibers are compromised. This indicates entrapment which may only be picked up with QST or in this case the negatives indicate a positive.
What do you think? Leave a comment, or better yet, let's discuss in person at one of our manual therapy courses coming up across the country!
*Abstract of the Week Shared by NAIOMT instructor Terry Pratt, MS, PT, COMT, FAAOMPT