SMALL FIBRE SENSORY TESTING
Previously I thought of neurological testing as part of the “ruling out” process when trying to identify patients with cervical radiculopathy and other conditions. After listening to the podcast and
reading this paper by Ridehalgh et al (2018), I can now see that it is important to examine both the large diameter and small diameter nerve fibres.
Ridehalgh, Sandy-Hindmarch & Schmid (2018) developed a testing procedure which involves combining warm/cold and mechanical pain threshold assessment to identify small fibre degeneration (SFD). Their results showed that:
Normal warm (WDT) or cold (CDT) sensation is highly sensitive (0.98) to rule out SFD, but has low specificity.
Reduction in pinprick is high specific (0.88) to rule in SFD.
Warm/cold detection
First the examiner used a coin at room temperature (cold testing) and assessed the lateral upper arm and palmar side of the index finger asking the patient to rate the temperature as same, colder or warmer. If the answer was “warmer at the finger” this would indicate a deficit in cold detection.
The the examiner would repeat the procedure with a coin that had been in their pocket for 30 minutes (warm testing).
No change in rating of cold/warm testing was interpreted as an indication that no small fibre degeneration was present.
Mechanical pain threshold
The examiner could use either a neurotip or toothpick.
The median nerve was tested by comparing detection of a “sharp” sensation at the ventral forearm and palmar tip of the index finger. Again the patient was asked to rate the sensation as same, sharper, less sharp.
The radial nerve was tested using the lateral upper arm and the palmar aspect of the index finger.
As you can see, both of these simple bedside tests for small fibre conduction can be easy to incorporate in your overall examination of a patient with potential TOS. I am eager to also try the CBSQ with suspected patients to assist with my overall clinical reasoning and differential diagnosis. I want to thank Jo Gibson and David Pope for sharing such valuable information on their blog and helping to guide me in the right direction with my assessment and management of these patients in the future.
Sian Smale is an Australian-trained Musculoskeletal Physiotherapist. Sian completed her Bachelor of Physiotherapy through La Trobe University in 2009 and in 2013 was awarded a Masters in Musculoskeletal Physiotherapy through Melbourne University. Since graduating from her Masters program, Sian has been working in a Private Practice setting and writing a Physiotherapy Blog "Rayner & Smale". Prior to moving to San Francisco, Sian worked at Physical Spinal and Physiotherapy Clinic and has a strong background in manual therapy and management of spinal spine, headaches and sports injuries. Since moving to the Bay area, Sian has become a Physiotherapist for the Olympic Winter Institute of Australia, traveling with their Para Alpine teams. Sian currently works full time at TherapydiaSF as a physical therapist and clinical pilates instructor.
instagram @siansmale_SF
References:
Hooper, T. L., Denton, J., McGalliard, M. K., Brismée, J.-M., & Sizer Jr, P. S. (2010). Thoracic outlet syndrome: a controversial clinical condition. Part 1: anatomy, and clinical examination/diagnosis. The Journal of manual & manipulative therapy, 18(2), 74.
Hooper, T. L., Denton, J., McGalliard, M. K., Brismee, J. M., & Sizer, P. S., Jr. (2010). Thoracic outlet syndrome: a controversial clinical condition. Part 2: non-surgical and surgical management. The Journal of manual & manipulative therapy, 18(3), 132-138.
Illig, K. A., Donahue, D., Duncan, A., Freischlag, J., Gelabert, H., Johansen, K., ... & Thompson, R. (2016). Reporting standards of the Society for Vascular Surgery for thoracic outlet syndrome. Journal of vascular surgery, 64(3), e23-e35.
Kaczynski, J., & Fligelstone, L. (2013). Surgical and Functional Outcomes After Thoracic Outlet Syndrome Decompression via Supraclavicular Approach: A 10-Year Single Centre Experience. Journal of Current Surgery, 3(1), 7-12.
Peet, R. M., Henriksen, J. D., Anderson, T., & Martin, G. M. (1956). Thoracic-outlet syndrome: evaluation of a therapeutic exercise program. Paper presented at the Proceedings of the staff meetings. Mayo Clinic.
Ridehalgh, C., Sandy-Hindmarch, O. P., & Schmid, A. B. (2018). Validity of clinical small–fiber sensory testing to detect small–nerve fiber degeneration. journal of orthopaedic & sports physical therapy, 48(10), 767-774.
Sanders, R. J. (2013). Anatomy of the Thoracic Outlet and Related Structures Thoracic Outlet Syndrome (pp. 17-24): Springer.
Sanders, R. J., Hammond, S. L., & Rao, N. M. (2007). Diagnosis of thoracic outlet syndrome. Journal of vascular surgery, 46(3), 601-604.
Watson, L. A., Pizzari, T., & Balster, S. (2009). Thoracic outlet syndrome part 1: Clinical manifestations, differentiation and treatment pathways. Manual therapy, 14(6), 586-595.
Watson, L. A., Pizzari, T., & Balster, S. (2010). Thoracic outlet syndrome Part 2: Conservative management of thoracic outlet. Manual therapy, 15(4), 305-314.
