Two variations of the median nerve described in the Lanz study as type 3 anomalies
were found during dissection. In the first case the median nerve splits in the cubital
fossa and descends through the carpal tunnel to the palm of the hand. In the second
of the reported cases the median nerve splits 45 mm before entering the carpal
tunnel and is accompanied by a persistent median artery. Surgeons should take such
variations into consideration in order to plan surgical approaches judiciously

A, Król

A, Palczak

KS, Jędrzejewski

English

Via Medica Journals

Folia Morphol. Vol. 64, No. 4, pp. 341–344Copyright © 2005 Via MedicaISSN 0015–5659www.fm.viamedica.plC A S E   R E P O R T341Address for correspondence: Aleksander Król, Department of Normal Anatomy, Medical University of Łódź, ul. Narutowicza 60, 90–136 Łódź,Poland, tel: +48 42 630 49 49, +48 42 630 07 49, e-mail: kajed@toya.net.plSplit median nerve. A report of two casesAleksander Król, Artur Palczak, Kazimierz S. JędrzejewskiDepartment of Normal Anatomy, Medical University of Łódź, Poland[Received 13 May 2005; Revised 3 November 2005; Accepted 3 November 2005]Two variations of the median nerve described in the Lanz study as type 3 anomalieswere found during dissection. In the first case the median nerve splits in the cubitalfossa and descends through the carpal tunnel to the palm of the hand. In the secondof the reported cases the median nerve splits 45 mm before entering the carpaltunnel and is accompanied by a persistent median artery. Surgeons should take suchvariations into consideration in order to plan surgical approaches judiciously.Key words: median nerve variations, split median nerve, persistentmedian artery, carpal syndromeINTRODUCTIONThe median nerve (MN) is often involved in patho-logical states such as the carpal tunnel syndrome orvarious injuries of the palm and forearm. Anomaliesof MN have been precisely described by Lanz [9] andcan be classified into four types: motor branch vari-ations, a distally arising accessory branch, a high di-vision of MN and a proximally arising accessorybranch. There have also been reports of a split MNaccompanied by a persistent median artery (PMA). Inthis study two Lanz type 3 anomalies are presented.MATERIAL AND METHODSThe two variations were found during routinedissection of upper limbs in the Department of Nor-mal Anatomy of the Medical University of Łódź. Thesespecimens were fixed with a 4% solution of formal-dehyde. The skin, the superficial fascia, the retinacu-lum flexorum and the aponeurosis palmaris wereremoved. In both cases observations were made ofthe limbs separated from the cadaver body.RESULTSIn the first of the cases presented MN origi-nates from the brachial plexus in the typical man-ner as a connection between two branches of thelateral and medial cord. In the arm MN runs downin the medial groove of the biceps muscle at firstlaterally and then posteriorly to the brachial ar-tery (BA). The MN then crosses the brachial arteryposteriorly before entering the cubital fossa. Thearteries of this limb do not show any divergencefrom the pattern usually described in manuals andtextbooks.In the cubital fossa the common trunk of MN di-vides into two branches. The major branch, as wehave termed it, which resembles a typical MN, pass-es between the heads of the pronator teres muscleand descends on the forearm under the flexor digi-torum superficialis muscle (FDSM).On exiting the carpal tunnel the major branchsplits into common digital nerves and gives branch-es to the thenar, a ramus palmaris passing throughthe retinaculum and a communicating branch withthe minor branch of MN (Fig. 1).The minor branch, which could be considereda third common digital nerve of MN of very earlyorigin, splits from MN, covered by the ulnoradial headof the pronator teres muscle, by which the minorbranch is also pierced. At the distal third of the fore-arm the minor branch lies on the tendons of FDSM,covered only by the palmaris longus muscle.The minor branch passes in the carpal tunnelcentrally and superficially to the flexor tendons.342Folia Morphol., 2005, Vol. 64, No. 4Before crossing the superficial palmar arch frombelow, the minor branch receives two connectingbranches: one from the ulnar nerve and the secondthe afore-mentioned communicating branch fromthe major branch. Finally the minor branch dividesinto two proper digital nerves, which innervate thelateral part of the of the fourth finger and the me-dial part of the third finger (Fig. 2).The second of the cases presented is an early di-vision of MN accompanied by a perisistent medianartery (PMA). The MN described divides into twobranches 45 mm before entering the carpal tunnel.In this case the minor branch does not receive anycommunicating branches. The minor branch, simi-larly to the minor branch of the first case, splits intotwo proper digital nerves at the level of the metac-arpophalangeal joints. The major branch divides intotwo common digital nerves at the level of the the-nar. In both cases only the major branch participatesin the thenar muscle innervation (Fig. 3).The PMA is a long but slender vessel which orig-inates from the ulnar artery and descends with MNto the palm of the hand. In the carpal tunnel PMA issituated superficially to the branches of MN On thepalm under the aponeurosis PMA splits into two com-mon digital arteries supplying the thumb, the sec-ond finger and the lateral part of the third finger.No connections were found with the ulnar artery orthe superficial branch of the radial artery.DISCUSSIONCases of a split MN are observed mostly dur-ing surgical interventions or anatomical dissection,more rarely during preoperative sonographic orMR imaging, and appear with a frequency rangeof 1–3% (2.8% according to the Lanz study [9]).The division occurs on different levels but mosttypically on the distal third of the forearm [1, 9].The minor branch is usually situated more super-ficially on the forearm than the major branch andpasses centrally through the carpal tunnel withthe flexor tendons, making it more susceptible tocompression and injury.The coexistence of the split MN with other anoma-lies, such as an abnormal insertion of a muscle or PMA,appears to be quite frequent [1, 8]. Ebied [6] de-scribes an improper insertion of the palmaris longusmuscle which entraps the split MN. Sanudo et al. [11]Figure 1. The bifurcation of the median nerve in the cubital fossa — first case; 1 — median nerve; 2 — major branch; 3 — minorbranch; 4 — ulnar head of the SDFM (pulled away).343Aleksander Król et al., Split median nerveFigure 3. Second case. 1 — major branch; 2 — PMA; 3 — minor branch.Figure 2. View of the distal forearm and carpus — first case; 1 — major branch; 2 — communicating branch from the major branch;3 — minor branch; 4 — communicating branch from the ulnar nerve; 5 — ulnar nerve; 6 — superficial palmar arch.344Folia Morphol., 2005, Vol. 64, No. 4present a highly dividing MN which forms a ringaround PMA just below the distal margin of thepronator teres muscle.The PMA has been described as originating fromthe ulnar, anterior interosseus, radial or brachial ar-tery [1, 10] and either terminates on the forearm ordescends to the palm of the hand. On the palm PMAmay, according to Coleman and Anson’s study [4],form an arch (medioulnar or radiomedioulnar) ordivide into its terminal branches without forming anysuperficial arterial connections. The PMA presentedoriginates from the ulnar artery and does not anas-tomose with any other superficial artery, making itresemble Coleman’s type 1.Variations of MN have, as some authors claim[3, 7, 13], significant clinical implications. The mi-nor branch is more susceptible to injury than thetypical MN [12]. Carpal tunel syndrome is morelikely to appear and presents more treatment prob-lems. When a bifid MN is encountered during sur-gical release both branches should be decom-pressed [13]. In some cases a split MN has forcedsurgeons to convert endoscopic to open release[3]. The PMA, because of prolonged compressionin the carpal tunnel, is more susceptible to throm-botic changes [2] and may also complicate treat-ment.In conclusion, emphasis should be put on knowl-edge of the variations of MN in order to avoid acci-dental injuries and also to increase the effectivenessof surgical approaches.REFERENCES1. Adachi B (1928) Das Arteriensytem der Japaner. Ada-chi B (ed.). Verlag der Kaiserlich-Japanischen Univer-sität zu Kyoto, Kyoto.2. Aulicino Pl, Klavans SM, Dupuy TE (1984) Digital is-chemia secondary to thrombosis of persistent medianartery. J Hand Surg, 9: 820–823.3. Cavallo AV, Slattery PG, Barton RJ (2003) Endoscopiccarpal tunnel release and congenital anomalies of themedian nerve. Hand Surg, 8: 265–270.4. Coleman SS, Anson BJ (1961) Arterial patterns in thehand based upon a study of 650 specimens. Surg Gy-necol Obstetr, 113: 409–424.5. Doyle J (2003) Surgical anatomy of the hand and up-per extremity. Lippincott Williams and Wilkins.6. Ebied AM (1999) Split median nerve. Microsurgery, 19:404–405.7. Ianniceli E, Chianta GA, Salvini V, Almberger M,Monaceli G, Passariello R (2000) Evaluation of bifidmedian nerve with sonography and MR imaging. J Ul-trasound Med, 19: 481–485.8. Lacoste P, Dalle M (1966) Anomalie arteriele de l’avant-bras et de la main. Essais d’interpretation embry-ologique. Compte rendus de l’Association des Anato-mist, 132: 563–570.9. Lanz U (1997) Anatomical variations of the mediannerve in the carpal tunnel. J Hand Surg, 2: 44–53.10. Lippert H, Pabst R (1985) Arterial variations in man.Springer, New York.11. Sanudo JR, Chkwe J, Evans SE (1994) Anomalous me-dian nerve associated with persistent median artery.J Anat, 185: 447–451.12. Sunderland S (1978) Nerves and nerve injuries. 2nd ed.Churchill Livingstone, New York.13. Takami H, Takahashi S, Ando M (2001) Bipartite mediannerve with double compartment within the transversecarpal canal. Arch Orthop Trauma Surg, 121: 230–231.

Split median nerve. A report of two cases

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Split median nerve. A report of two cases

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