3/4/2019 9:28:29 AM
Seeking insight on a finding in the evaluation of carpal tunnel evaluations
I am hopeful that I can obtain some insight regarding a particular finding in the evaluation of carpal tunnel evaluations that I am seeing from time-to-time. Specifically, I perform a 14/7 cm antidromic SNAP study and obtain a mid-palm latency of 1.9 ms with an amplitude of 20 uV and a 14 cm SNAP with a latency of 4.4 ms and amplitude of 15 uV. I am comfortable with an assessment of focal slowing of the median sensory fibers to the third digit across the wrist consistent with the diagnosis of the patient’s clinical symptoms of CTS. However, when performing the median CMAP evaluation, I obtain a 8 cm wrist value of 3.8 ms with an amplitude of 7 mV and an antecubital fossa result of 7.7 ms, with a resulting conduction velocity of 46 M/s. The median motor DML appears fine as does the amplitude, but the NCV is low. The temperature over the APB is 34 degrees C, and I have checked and re-checked my distance. What is going on?