s1042368008000119.pdf

Neurosurg Clin N Am 19 (2008) 217–238

Selection of Surgical Approach to Acoustic Neuroma

Robert K. Jackler, MD * , Lawrence H. Pitts, MD

Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, USA

Centers with special expertise in the manage-

ment of acoustic neuromas fall into three broad

categories in terms of their preference for operative

approaches: (1) suboccipital preferred, (2) trans-

labyrinthine preferred, and (3) eclectic. The number

of teams in the last group has steadily grown in

recent years as cooperating neurotologists and

neurosurgeons have become aware of the relative

advantages and disadvantages of the various tech-

niques [1–4] . At the University of California, San

Francisco (UCSF), we use amixture of the subocci-

pital, translabyrinthine, and middle fossa ap-

proaches according to the characteristics of the

particular tumor undergoing treatment. In this ar-

ticle, we review the anatomic and clinical factors af-

fecting the choice of operative approach, examine

the diﬀerences in postoperative outcome among the

surgical techniques, and present a protocol for the

selection of approach based on tumor size and

clinical manifestations.

very large acoustic neuromas. A few authors,

who limit their practice to the suboccipital

approach, have maintained that the translabyrin-

thine approach aﬀords insucient exposure for

larger tumors. This point of view was well articu-

lated by DiTullio, Malkasian, and Rand, who

maintained that ‘‘because of the limited operative

ﬁeld, this approach precludes adequate visualiza-

tion not only of the medial aspect of the tumor

but also its anatomical relationship to the vital

brain stem and vascular structures’’ [5] . In con-

trast to the opinion expressed by these authors,

we have found that the exposure of the brain

stem surface facing an acoustic neuroma provided

by the two approaches is essentially identical.

Much of the criticism of the exposure provided

by the translabyrinthine approach has undoubt-

edly arisen when neurosurgeons collaborated

with inexperienced temporal bone surgeons who

provided an insucient transtemporal exposure

of the posterior fossa. It should be emphasized

that adequate exposure of the cerebellopontine an-

gle for large tumors by the translabyrinthine ap-

proach requires that the surgeon perform a wide

retrosigmoid decompression of the posterior fossa

dura, remove bone from the jugular bulb and hor-

izontal course of the sigmoid sinus, and excavate

well anterior to the porus acusticus. We also dis-

agree that there are neurotologic and neurosurgi-

cal approaches to acoustic neuroma. Both the

translabyrinthine and suboccipital approaches

are posterior fossa craniotomies that diﬀer primar-

ily in the way the head is opened. The essential is-

sue at hand, the removal of the intracranial tumor,

properly resides within the armamentarium of

both specialties, depending on the surgeon’s train-

ing, experience, and microsurgical skills.

On ﬁrst reﬂection, it may seem that the

angle of view of the internal auditory canal,

Factors aﬀecting the choice of surgical technique

Tumor size

For almost all acoustic neuromas removed at

UCSF, we select either the translabyrinthine or

suboccipital approach ( Fig. 1 ). Tumor size, in and

of itself, is not a criterion in choosing between the

translabyrinthine and suboccipital techniques

when removing an acoustic neuroma. Either

approach provides a sucient exposure of the

cerebellopontine angle and brain stem to permit

atraumatic and complete tumor removal of even

This article originally appeared in The Otolaryngologic

Clinics of NA: Vol 25, issue 2, April 1992; p. 361–388.

* Corresponding author. 801 Welch Road, Stanford,

CA 94305-5739.

doi:10.1016/j.nec.2008.02.010

neurosurgery.theclinics.com

218

JACKLER & PITTS

Fig. 1. Schematic view of suboccipital, translabyrinthine, retrolabyrinthine, and transcochlear approaches to the

cerebellopontine angle as visualized in the axial plane.

cerebellopontine angle, and brain stem provided

by the translabyrinthine and suboccipital ap-

proaches are quite diﬀerent. After all, the areas

of skull removed are quite separate, having only

1 to 2 cm of overlap behind the sigmoid sinus.

Nevertheless, the exposure aﬀorded by the two

techniques is remarkably similar. The explanation

for this lies in the fact that the angle of view

employed is actually almost identical. In the

translabyrinthine approach, the surgeon retrodis-

places the sigmoid sinus and looks along this

posterior aspect of the craniotomy opening

( Figs. 2 and 3 ). In the suboccipital approach, the

surgeon removes bone up to the sigmoid sinus

and then views along the most anterior edge of

the craniotomy ( Figs. 4, 5, and 6 ). In the average

exposure, the angle of view of a translabyrinthine

craniotomy is slightly more lateral and that of the

Suboccipital more posterior, but this diﬀerence is

usually less than a 10 degree angle.

Although the translabyrinthine approach pro-

vides excellent visualization of the internal audi-

tory canal and cerebellopontine angle, it does not

create as panoramic a view of the posterior fossa

as the suboccipital approach. The translabyrin-

thine exposure, especially when the jugular bulb is

high, is limited inferiorly. This may restrict access

to the inferior-most portion of the cerebellopon-

tine angle, the neural compartment of the jugular

foramen, and to the foramen magnum region.

This limitation is seldom problematic during

surgery on acoustic neuromas because these

SELECTION OF SURGICAL APPROACH TO ACOUSTIC NEUROMA

219

Fig. 2. Translabyrinthine approach viewed schematically in axial section (A) and from the surgeon’s viewpoint (B) dem-

onstrating key points of anatomy. JV, jugular veinz; JB, jugular bulb; SS, sigmoid sinus; TS, transverse sinus; SPS, superior

petrosal sinus; Cb, cerebellum; D, retrosigmoid dura; Ca, cochlear aqueduct; IV, inferior vestibular nerve; SV, superior

vestibular nerve; 5, trigeminal nerve; 6, abducens nerve; 7, facial nerve; 8, audiovestibular nerve; 9, glossopharyngeal nerve;

10, vagus nerve; 11, accessory nerve; GG, geniculate ganglion; Ch, choroid, Fl, ﬂocculus.

220

JACKLER & PITTS

Fig. 3. Translabyrinthine approach to a medium-sized acoustic neuroma. Inspection of the lateral end of the internal

auditory canal reveals that the tumor originated from the superior vestibular nerve. Note deformation of the facial nerve

over the ventral surface of the tumor.

tumors rarely extend very far inferiorly, and when

they do, the lower pole of the tumor can be readily

mobilized into the operative ﬁeld. This is not the

case for meningiomas, epidermoids, and other

tumors, however, that tend to adhere to the lower

cranial nerves and vertebrobasilar system. When

a coronal magnetic resonance imaging (MRI)

scan reveals an unusual degree of inferior tumor

extension, especially when a non–acoustic neu-

roma tumor is suspected, we choose the subocci-

pital approach.

The middle fossa approach is generally con-

sidered to be suitable only for wholly intracana-

licular lesions ( Figs. 7 and 8 ). A few authors have

advocated an extended middle fossa approach in

the management of tumors with large cerebello-

pontine angle components [7–8] . They point out

that through extensive removal of the temporal

ﬂoor, accompanied by division of the superior pe-

trosal sinus and a portion of the tentorium, a lim-

ited exposure to the cerebellopontine angle may

be obtained via the middle fossa approach. In

our opinion, this variation aﬀords insucient ex-

posure of the inferior aspect of the cerebellopon-

tine angle to assure control of vessels arising

beneath the tumor. Also, the extended middle

fossa approach to the cerebellopontine angle re-

quires rather vigorous and prolonged retraction

of the temporal lobe, a maneuver less forgiving

than comparable displacement of the cerebellum.

For these reasons, the extended middle fossa tech-

nique has not gained widespread acceptance.

Depth of internal auditory canal penetration

Each of the three major approaches to acoustic

neuroma is capable of completely exposing the

contents of the internal auditory canal for

removal of the intracanalicular portion of the

tumor. Only the middle fossa technique permits

complete canal opening without violation of the

inner ear. In the translabyrinthine approach, the

SELECTION OF SURGICAL APPROACH TO ACOUSTIC NEUROMA

221

Fig. 4. Suboccipital approach viewed schematically in axial section (A) and from the surgeon’s viewpoint demonstrating

key points of anatomy (B). Note that the inner ear overlaps the lateral one third of the distal internal auditory canal. JV,

jugular vein; JB, jugular bulb; SS, sigmoid sinus; 11S, spinal division of the accessory nerve; 11C, cranial division of the

accessory nerve; 10, vagus nerve; 9, glossopharyngeal nerve; ES, endolymphatic sac; VA, vestibular aqueduct; PSCC,

posterior semicircular canal; CC, common crus; SSCC, superior semicircular canal; Co, cochlea; IV, inferior vestibular

nerve; SV, superior vestibular nerve; PA, poms acusticus; 7, facial nerve; 8, audiovestibular nerve; Ch, choroid; Fl, ﬂocculus;

BS, brain stem; 5, trigeminal nerve.

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