J Neurosurg 75:985-986, 1991
Anomalous subarcuate loop Technical note ATUL GOEI., M.CH., ANt~ LAHGAM N. SEKtlAR, M.D.
CentreJor Cranial Base Surgeo,, Presbyterian University Ho.sl~itat, Pittsburgh, Pennsylvania An anomalous subarcuate loop of the anterior inferior cerebellar artery is described in which the arlcry is adherent to or penetrates the posterior fossa dura in the subarcuate fossa. When encountered during acoustic neurilemoma surgery, the artery should be carefidly mobilized along with a sleeve of dura to prevent its injury. KEY WORDS 9 acoustic neurinoma 9 anterior inferior cerebellar artery cerebellopontine angle . anomalous vessel
N this report, we describe an anomalous postmeatal subarcuate loop of the anterior inferior cerebellar artery (AICA) encountered during surgery for acoustic neurilemomas. The surgeon should be aware of this possibility so that damage to the artery can be avoided.
In approximately 300 operations in the cerebelloponfine angle performed by the senior author (L.N.S.), three cases were encountered in which the AICA traversed the dura overlying the posterior surface of the petrous bone and subarcuate fossa. The attachment of the artery to the posterior surface of the petrous bone prevented a conventional surgical approach to the internal auditory meatus and canal (Fig. 1). Accordingly, in all three cases the artery, along with a sleeve of the surrounding dura, was dissected from the bone as shown in Fig. 2. A tiny vessel, probably the subarcuate artery, bled as the AICA was elevated from the bone. This was controlled by bipolar cautery without occlusion of the AICA and waxing of the petrous bone. Surgery for the acoustic neurinoma was then completed. Discussion
Martin, et al.) studied the cerebellopontine angles in 50 cadavefic specimens and found 17 cases of a laterally
J. Neurosurg. / Volume 75 /December. 1991
FIG. 1. Intraoperative photograph (upper) and line drawing (lower) showing the anomalous subarcuate loop of anterior inferior cerebellar artery. (AICA) traversing 'the dura on the posterior surface of the petrous bone in the cerebelloponfine angle. Roman numerals denote cranial nerves. 985
A. Goel and L. N. Sekhar brain-stem infarction and death if the postmeatal segment of the AICA is clipped during surgery for acoustic nerve-sheath tumors. "4'6 The danger of brain-stem infarction is more likely if the ipsilateral posterior inferior cerebellar artery is rudimentary. ~ Coagulation of the AICA may' lead to hearing loss5 or facial palsy. This artery can inadvertently be ruptured during retraction of the cerebellum away from the posterior surface of the petrous bone if it is densely adherent to or traverses through the dura. Surgeons managing cerebellopontine angle tumors should be aware of this possibility. References
FIG. 2. Photograph O*pper) and line drawing (lower) showing retraction of the anterior inferior cerebellar artery, (AICA) with the dura, exposing the tumor. Roman numerals denote cranial nerves.
convex curve of the AICA directed toward the subarcuate fossa. They called it "the subarcuate loop." They also discovered that the apex of the loop was occasionally adherent to the dura over the subarcuate fossa at the point where the subarcuate artery arose. Lang 2 found in 6% of his dissections that the subarcuate loop was either traversing the dura or actually piercing through the bone of the region. Various authors have described the possibility of
1, Atkinson WJ: Anterior inferior cerebellar artery; its variations, pontine distribution, and significance in surgery of cerebello-pontine angle turnouts. J Neurol Neurosurg Psychiatry 12:137-15 I, 1949 2. Lang J: Posterior cranial fossa and temporal bone, in Sekhar LN, Janecka I (eds): Surgery for Skull Base Tumors. A Color Atlas. New York: Raven Press (In press, 1992) 3. Martin RG, Grant JU Peace D, et al: Microsurgical relationships of the anterior inferior cerebellar artery, and the facial-vestibuloeochlear nerve complex. Neurosurgery 6:483-507, 1980 4. Rhoton AL Jr, Kobayashi S, Hollinshead WH: Nervus intermedius, J Neurosurg 29:609-618, 1968 5. Samii M: Microsurgery of acoustic neurinomas with special emphasis on preservation of the seventh and eighth cranial nerves and the scope of facial nerve grafting, in Rand RW (ed): Microneurosurgery, ed 3. St Louis: CV Mosby, I985, pp 366-388 6. Sunderland S: The arterial relations of the internal auditory, meatus. Brain 68:23-27, 1945 Manuscript received December 19, 1990. Accepted in final form April 29, 1991. Address for Dr. God: Department of Neurosurgery, K.E.M. Hospital, Pard, Bombay 400 012, India. Address reprint reqttests to. Laligam N. Sekhar, M.D., Department of Neurological SurgeD', 9402 Presbyterian University Hospital, 230 Lothrop Street, Pittsburgh, Pennsylvania 15213.
J, Neurosurg. / Volume 7,5/December, 1991