PMC6445876_01
(A) The ulnar nerve compound motor action potential at the abductor digiti minimi (ADM) shows 65% drop in amplitude with 30% drop in the area and 63% prolongation in the duration when the nerve is stimulated below the elbow as compared to stimulation at the wrist. There was a slowing in conduction velocity across the elbow. The last trace, shows no motor response from ADM when stimulating the median nerve at the elbow. (B) The ulnar nerve compound motor action potential at the first dorsal interossei (FDI) shows 47% drop in amplitude with 53% drop in the area and 17% prolongation in the duration when the nerve is stimulated below the elbow as compared to stimulation at the wrist. There was a slowing in conduction velocity across the elbow. (C) The last area where the amplitude was partially maintained before the 63% amplitude drop occurred (when recording from ADM) 6 cm below the elbow, indicating that the maximum area of focal demyelination occurs just proximal to that point at around 5 cm below the elbow.
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F1
The ulnar motor conduction amplitude when distally stimulating the ulnar nerve and recording at the abductor digiti minimi at the wrist was normal; however, there was a 63% amplitude drop when stimulating below the elbow compared to distal stimulation at the wrist (Figure 1A). There was no motor response from ADM when stimulating the median nerve at the elbow (Figure 1A). In addition, ulnar motor conduction amplitude when stimulated below the elbow and recorded at the first dorsal interossei showed a 47% amplitude drop when compared to distal stimulation at the wrist (Figure 1B). In order to rule out pathology in the forearm on the right that might explain the conduction block, we traced the right ulnar nerve motor potential up to the elbow (Figure 1C).
Surgical photograph of the right elbow demonstrating the released ulnar nerve from the cubital tunnel placed over the flexor muscle mass, in preparation to complete the transposition under a fascial sling. The edematous segment of the ulnar nerve shown is the segment that normally runs between the two heads of FCU muscle. The red vessel loop encircles the posterior branches of the medial antebrachial cutaneous nerve that crosses the surgical incision.
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F2
Surgical transposition was conducted and showed nerve swelling distal to the medial epicondyle between the two heads of FCU (Figure 2). FCU and the HUA with no additional cause of entrapment was identified at that segment during the surgical exploration (Figure 2). Follow up at 6 months after the surgery, the patient has reported complete resolution of the symptoms including absence of tingling sensation and normal sleep.