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.

Although numerous reports have found accessory or supernumerary muscles throughout the human body, multiple appearances of these variations biased toward one side of body are rare. We report a 76-yr-old male cadaver with an accessory head of the biceps brachii and palmaris profundus, and a muscular slip between the biceps femoris and semitendinosus on the left side in addition to a bilateral accessory belly of the digastric muscle. No remarkable nervous, vascular, or visceral variation accompanied these variations. An interruption of normal somitogenesis or myogenesis may be a cause of these variations.

IntroductionThe axillary and cephalic veins are used for various clinical purposes but their anatomy is not fully understood. Increased knowledge and information about them as well as superficial veins in the upper arm would be useful.ObjectiveThe aim of this study is to contribute to the literature regarding the anatomy of the venous drainage of the upper extremity.MethodsThe veins of forty upper extremities from twenty one adult cadavers were injected and their axillary regions dissected. The course and pattern of drainage of the venous tributaries in the axillary region were identified and recorded.ResultsThe basilic, brachial, subscapular, lateral thoracic and superior thoracic veins drained mainly into the axillary vein, in common with most textbook descriptions. However, the thoracoacromial veins were observed to drain into the cephalic vein in 70.0% of upper limbs. In addition, a venous channel connecting the distal part and proximal part of the axilla was found along the posterolateral wall of the axilla in 77.5% of the upper limbs. In 95.0% of upper limbs, we discovered a superficial vein which ran from the axillary base and drained directly into the axillary vein.ConclusionThe veins from the inferomedial part of the axilla drain into the axillary vein, whereas the veins from the superolateral part of the axilla drain into the cephalic vein. The venous drainage of the axilla is variable and in common with venous drainage elsewhere, does not necessarily follow the pattern of the arterial supply.

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