Duplicated abducent nerve and its course: microanatomical study and surgery-related considerations

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Object. The anatomy of the abducent nerve is well known; its duplication (ranging from 5 to 28.6%), however, has rarely been reported in the literature. The authors performed a microanatomical study in 100 cadaveric specimens (50 heads) to evaluate the prevalence of this phenomenon and to provide a clear anatomical description of the course and relationships of the nerve. The surgery-related implications of this rare anatomical variant will be highlighted.

Methods. The 50 human cadaveric heads (100 specimens) were embalmed in a 10% formalin solution for 3 weeks. Fifteen of them were injected with colored neoprene latex. A duplicated abducent nerve was found in eight specimens (8%). In two (25%) of these eight specimens the nerve originated at the pontomedullary sulcus as two independent trunks: in one case the superior trunk was thicker than the inferior and in the other it was thinner. In the other six cases (75%) the nerve originated as a single trunk, splitting in two trunks into the cisternal segment: in two of them the trunks ran below the Gruber ligament, whereas in four specimens one trunk ran below and one above it. In all the specimens, the duplicated nerves fused again into the cavernous sinus, just after the posterior genu of the internal carotid artery.

Conclusions. Although the presence of a duplicated abducent nerve is a rare finding, preoperative magnetic resonance imaging should be performed to rule out this possibility, thus tailoring the operation to avoid postoperative deficits.

Article Information

Address reprint requests to: Giorgio Iaconetta, M.D., Via Gravina, 2, 80055 Portici (NA), Italy. email: iaconetta@libero.it.

© AANS, except where prohibited by US copyright law.

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Figures

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    Intraoperative photographs. Left: Left presigmoid approach. The abducent nerve originates as two independent trunks piercing the dura mater in two different pores (arrowheads). The seventh–eighth cranial nerve complex has been reflected downward (arrow). Right: Right presigmoid approach. It is possible to visualize the two root exit zones of the nerve trunks (arrows).

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    Intraoperative photographs. Upper: Right side. The cavernous sinus and posterior fossa are opened after drilling the petrous bone and removing the tentorium; the trigeminal ganglion, V1, V2, and V3 have been resected. Both nerve trunks ran below the Gruber ligament and were posteriorly reflected (arrowhead); they are in close relationship with the posterior bend of the ICA, fusing at the level of the horizontal portion of the vessel (arrow). The cavity of Meckel can also be observed (double arrows). Lower: Right subtemporal transpetrosal approach. The basilar artery (BA) gives rise to two AICAs. The duplication of the abducent nerve is then associated with a double AICA. The superior AICA (arrow) passes between the two trunks (arrowheads), elevating the thicker one in proximity of the root exit zone.

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    Intraoperative photograph demonstrating the left presigmoid approach. The abducent nerve splits into two trunks, piercing the petroclival dura in two different pores.

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    Intraoperative photograph showing the right cavernous sinus opened; the trigeminal ganglion, V1, V2, and V3 have been resected. The fusion point of the two trunks (arrow) can be appreciated on the lateral wall of horizontal ICA.

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    Intraoperative photograph demonstrating the abducent nerve on the right side. The cavernous sinus, superior orbital fissure, and orbital roof have been opened. The anulus of Zinn has been resected. The abducent nerve passes through the superior orbital fissure and runs laterally to reach the lateral rectus muscle. The terminal branches of the nerve can also be seen (arrow).

References

  • 1.

    Bremer JL: Aberrant roots and branches of the abducent and hypoglossal nerves. J Comp Neurol 18:6196391908Bremer JL: Aberrant roots and branches of the abducent and hypoglossal nerves. J Comp Neurol 18:619–639 1908

  • 2.

    Brunner FX: Über die Arterien des Hirnstammes Vorkommen Zahl Durchmesser und Variationen. DissertationUniversity of WurzburgWurzburg, Germany1978Brunner FX: Über die Arterien des Hirnstammes Vorkommen Zahl Durchmesser und Variationen. Dissertation University of Wurzburg Wurzburg Germany 1978

  • 3.

    Destrieux CVelut SKakou Met al: A new concept in Dorello's canal microanatomy: the petroclival venous confluence. J Neurosurg 87:67721997Destrieux C Velut S Kakou M et al: A new concept in Dorello's canal microanatomy: the petroclival venous confluence. J Neurosurg 87:67–72 1997

  • 4.

    DiDio LJBaptista CATeofilovski-Parapid G: Anatomical variations of the abducent nerve in humans. Arch Ital Anat Embriol 95:1671721990DiDio LJ Baptista CA Teofilovski-Parapid G: Anatomical variations of the abducent nerve in humans. Arch Ital Anat Embriol 95:167–172 1990

  • 5.

    Dorello P: Considerazioni sopra la causa della paralisi transitoria dell'abducente nelle flogosi dell'orecchio medio in Ferrari G (ed): Atti della Clinica Oto-Rino-Laringoiatrica. Roma: Tipografia del Campidoglio1905 pp 209217Dorello P: Considerazioni sopra la causa della paralisi transitoria dell'abducente nelle flogosi dell'orecchio medio in Ferrari G (ed): Atti della Clinica Oto-Rino-Laringoiatrica. Roma: Tipografia del Campidoglio 1905 pp 209–217

  • 6.

    Iaconetta GFusco MPütz KMet al: La confluenza venosa sfeno-petro-clivale. Studio anatomo-chirurgico su cadavere. XLVIII National Congress of Italian Neurosurgical Society. Copanello, Italy: NCINS1999 p 102 (Abstract)Iaconetta G Fusco M Pütz KM et al: La confluenza venosa sfeno-petro-clivale. Studio anatomo-chirurgico su cadavere. XLVIII National Congress of Italian Neurosurgical Society. Copanello Italy: NCINS 1999 p 102 (Abstract)

  • 7.

    Jain KK: Aberrant roots of the abducent nerve. J Neurosurg 21:3493511964Jain KK: Aberrant roots of the abducent nerve. J Neurosurg 21:349–351 1964

  • 8.

    Knosp EMuller GPerneczky A: The blood supply of the cranial nerves in the lateral wall of the cavernous sinus in Dolenc VV (ed): The Cavernous Sinus. New York: Springer-Verlag1987 pp 6780Knosp E Muller G Perneczky A: The blood supply of the cranial nerves in the lateral wall of the cavernous sinus in Dolenc VV (ed): The Cavernous Sinus. New York: Springer-Verlag 1987 pp 67–80

  • 9.

    Krisht ABarnett DWBarrow DLet al: The blood supply of the intracavernous cranial nerves: an anatomical study. Neurosurgery 34:2752791994Krisht A Barnett DW Barrow DL et al: The blood supply of the intracavernous cranial nerves: an anatomical study. Neurosurgery 34:275–279 1994

  • 10.

    Lang J: Eintritt und Verlauf der Hirnnerven (III, IV, VI) “im” Sinus cavernosus. Z Anat Entwicklungsgesch 145:87991974Lang J: Eintritt und Verlauf der Hirnnerven (III IV VI) “im” Sinus cavernosus. Z Anat Entwicklungsgesch 145:87–99 1974

  • 11.

    Lang J: Skull Base and Related Structures. Stuttgart: Schattauer1995 pp 8586Lang J: Skull Base and Related Structures. Stuttgart: Schattauer 1995 pp 85–86

  • 12.

    Marinkovic SVGibo HStimec B: The neurovascular relationships and the blood supply of the abducent nerve: surgical anatomy of its cisternal segment. Neurosurgery 34:101710261994Marinkovic SV Gibo H Stimec B: The neurovascular relationships and the blood supply of the abducent nerve: surgical anatomy of its cisternal segment. Neurosurgery 34:1017–1026 1994

  • 13.

    Nathan HOuaknine GKosary IZ: The abducens nerve. Anatomical variations in its course. J Neurosurg 41:5615661974Nathan H Ouaknine G Kosary IZ: The abducens nerve. Anatomical variations in its course. J Neurosurg 41:561–566 1974

  • 14.

    Testut L: Anatomia Umana (Anatomia Descrittiva—Istologia— Sviluppo)ed 3. Torino: Unione Tipografico—Editrice Torinese1943Testut L: Anatomia Umana (Anatomia Descrittiva—Istologia— Sviluppo) ed 3. Torino: Unione Tipografico—Editrice Torinese 1943

  • 15.

    Tillack TWWiner JA: Anomaly of the abducent nerve. Yale J Biol Med 34:6206241962Tillack TW Winer JA: Anomaly of the abducent nerve. Yale J Biol Med 34:620–624 1962

  • 16.

    Tschabitscher MDoskar K: Eine Lagebeziehung zeischen Nervus abducens und Kleinhirnarterien. Anat Anz 134:2112141973Tschabitscher M Doskar K: Eine Lagebeziehung zeischen Nervus abducens und Kleinhirnarterien. Anat Anz 134:211–214 1973

  • 17.

    Umanski FElidan JValarezo A: Dorello's canal: a micro-anatomical study. J Neurosurg 75:2942981991Umanski F Elidan J Valarezo A: Dorello's canal: a micro-anatomical study. J Neurosurg 75:294–298 1991

  • 18.

    Umanski FValarezo AElidan J: The microsurgical anatomy of the abducens nerve in its intracranial course. Laryngoscope 102:128512921992Umanski F Valarezo A Elidan J: The microsurgical anatomy of the abducens nerve in its intracranial course. Laryngoscope 102:1285–1292 1992

  • 19.

    Watt CJMcKillop AN: Relation of arteries to roots of nerves in posterior cranial fossa in man. Arch Surg 30:3363451935Watt CJ McKillop AN: Relation of arteries to roots of nerves in posterior cranial fossa in man. Arch Surg 30:336–345 1935

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