Double anastomosis of median-ulnar and ulnar-median nerves: report of an electrophysiologically proven case

From the brachial plexus to the hand, multiple connections between the median and ulnar nerves may serve as bypass routes for nerve fibres

Axons from the median and ulnar nerves can pass to each other through aberrant connections between them. Multiple interconnections between the nerves may provide a detour route for nerve fibres going to the hand. We investigated the incidence of variations and the associations between them in 90 cadaveric upper limbs. In 91% of upper limbs, one to five variations were found, with several statistically significant associations. The contribution of the C8 nerve to the lateral cord was positively associated with an accessory contribution of the lateral cord to the ulnar nerve. The latter variation showed positive association with the occurrence of any of the variations in the hand itself. Ulnar innervation of the superficial head of the flexor pollicis brevis was positively associated with the Riche-Cannieu communication. The co-existence of the variations and their associations may be the explanation for unusual clinical findings related to median and ulnar conduction, which appear contrary to anatomical knowledge.

Ulnar Dominant Hand and Forearm

An ulnar-to-median anastomosis in the forearm is a rare condition, but may be present in any electromyographic case. A thorough approach to this condition is required to avoid misinterpretation of the electrodiagnostic report and confusion during the test. Prior to concluding that an anomaly is present, technical reason should be taken into consideration. The presence of volume-conducted potentials from various nearby muscles may confuse the electromyographer. Therefore, instead of using surface electrodes with unintended supramaximal intensity of stimulation, the needle electrodes may be used (in some cases) to localize specific muscles and to minimize volume-conducted potentials by not utilizing supramaximal stimulation intensity. The authors will discuss ulnar-to-median anastomosis in the forearm. This is the first attempt to put together all the information available in the literature about such an anastomosis.

[Constitutional anomalies of the terminal branches of the brachial plexus in the axial and brachial regions. Results of 42 cases and review of the literature]

The authors report anatomical variations of the terminal brachial plexus branches in 42 cadaveric dissections. The results are compared with results reported in literature which revealed a new variation: ulnar nerve originating in posterior beam. This study demonstrates that there exist not one but several brachial plexes which could have potential clinical implications.

Median-ulnar anastomosis to thenar, hypothenar, and first dorsal interosseous muscles: collision technique confirmation

Median-ulnar anastomosis (Martin-Gruber anastomosis; MGA) is traditionally diagnosed based upon changes in compound muscle action potential (CMAP) amplitude following proximal stimulation. We describe a rare patient with a MGA innervating thenar, hypothenar, and first dorsal interosseous muscles. Proximal stimulation, however, evoked CMAPs with striking changes in morphology and area but only minimal amplitude changes, due to concomitant diagnoses of carpal tunnel syndrome and polyneuropathy. Collision studies were therefore required for diagnostic confirmation of the MGA.