s1042368008000089.pdf

Neurosurg Clin N Am 19 (2008) 251–264

Translabyrinthine Approach for Acoustic

Tumor Removal

Derald E. Brackmann, MD a , * , J. Douglas Green, Jr, MD b

a House Ear Clinic and Institute, Los Angeles, California (DEB); and the Mayo Clinic, Jacksonville, Florida (JDG)

b Jacksonville Hearing and Balance Institute, 10475 Centurion pky N, Jacksonville, FL 32256, USA

The translabyrinthine approach is the most

direct route to the cerebellopontine angle. We

believe that this approach oﬀers many advantages

for acoustic tumor removal. In this article, the

indications and relative contraindications for the

approach are outlined. The surgical technique is

then detailed and illustrated.

approach. Perforations of the tympanic mem-

brane should ﬁrst be repaired, following which

the translabyrinthine approach may be used

when healing has occurred. In the case of

a mastoid cavity, a total obliteration is ﬁrst

performed with blind sac closure of the external

auditory canal. The translabyrinthine approach

may then be performed when healing has

occurred. A relative contraindication is a patient

who has good hearing and a tumor amenable to

a hearing conservation approach as already

described.

Indications

Small tumors that extend no further than

5 mm into the cerebellopontine angle in patients

with good hearing are usually approached via the

middle fossa [1] . Larger tumors in which good

hearing remains are approached via the retrosig-

moid route. This route is ideal when the tumor

arises more medially and is not impacted into

the fundus of the internal auditory canal and

does not expand the canal.

In general, the outlook for hearing preserva-

tion for acoustic tumors with greater than 2 cm

extension into the cerebellopontine angle is very

poor. These tumors and all tumors with poor

hearing are removed via the translabyrinthine

approach. There is no tumor too large to be

approached via the translabyrinthine route. For

large tumors, more bone removal is accomplished

posterior to the sigmoid sinus to gain access.

Advantages

The translabyrinthine approach oﬀers several

advantages for acoustic tumor removal. It re-

quires a minimum of cerebellar retraction. Expo-

sure and dissection of the lateral end of the

internal auditory canal ensures complete tumor

removal from that area and allows positive

identiﬁcation of the facial nerve at a consistent

anatomic location [2] .

If the facial nerve is lost during acoustic tumor

removal, the translabyrinthine approach oﬀers the

best opportunity for immediate repair by end-to-

end anastomosis or interposition of a nerve graft

[3] .

Contraindications

There is a lower incidence of cerebrospinal

ﬂuid leaks with this approach compared with the

retrosigmoid approach.

Finally and most importantly, this approach

carries the lowest morbidity and mortality. The

mortality rate for this approach is 0.4% for the

last 2300 cases [4] . Experienced teams performing

the retrosigmoid approach are reporting nearly

equivalent mortality rates.

The presence of chronic otitis media is

a contraindication for the translabyrinthine

The article is originally appeared in Otolaryngologic

Clinics of NA: Vol. 25, issue 2, April; 1992. p. 311–330.

* Corresponding author: House Ear Clinic, 2122

West Third Street, Los Angeles, CA 90057.

doi:10.1016/j.nec.2008.02.007

neurosurgery.theclinics.com

252

BRACKMANN & GREEN

Limitations

toward the opposite side and maintained in

a natural position without ﬁxation. The surgeon

is then seated at the patient’s side. This position

minimizes fatigue and allows stabilization of the

arms and hands during the exacting microsurgical

procedures ( Fig. 1 ).

The obvious disadvantage of the translabyrin-

thine approach is the sacriﬁce of any residual

hearing in the operated ear. The approach is

therefore reserved for patients whose hearing is

poor or for large tumors in which the possibility

of hearing preservation is slight.

In the past, it has been said that the approach

is limited to smaller tumors. As already stated, we

have not found this to be true. There is no tumor

too large to be approached translabyrinthine. In

fact, we believe that there are advantages for large

and giant tumors in that the approach puts one

directly into the center of the tumor at its origin.

Intracapsular removal of the tumor allows the

capsule to be displaced toward the opening by

surrounding brain structures.

Instruments

Standard neurotologic instruments are used.

One special instrument s used and is discussed

later.

Anesthesia

General endotracheal anesthesia with inhala-

tion agents is used. Muscle relaxants are used only

for induction of anesthesia because intraoperative

monitoring of facial nerve activity is routinely

used. Prophylactic antibiotics or steroids are not

routinely used. Occasionally with very large

tumors these measures are employed. A nasogas-

tric tube and Foley catheter are placed after the

patient is asleep.

Technique

Preparation for surgery

The patient is placed supine on the operating

table with the head at the foot of the table. This

allows the anesthesiologist, who is seated at the

patient’s feet, easy access to the controls for

moving the table. The patient’s head is turned

Operative technique

The suboccipital area, pinna, and ear canal are

prepared with povidone-iodine (Betadine

Fig. 1. Room arrangement for the translabyrinthine aproach. Note positions of surgeon, anesthesiologist, and nurse.

TRANSLABYRINTHINE APPROACH FOR ACOUSTIC TUMOR REMOVAL

253

solution), and plastic drapes are applied. A

postauricular incision is made approximately

2 cm behind the postauricular crease ( Fig. 2 ).

The incision is curved anteriorly to allow anterior

retraction of the pinna. The posterior curve of the

incision allows access to the area behind the

sigmoid sinus. Because most of the surgical view

of the cerebellopontine angle is along the plane

of the posterior fossa dura, posterior access is

important.

The incision ﬁrst extends to the fascia tempo-

ralis, and the dissection is carried to the linea

temporalis, lateral to the fascia temporalis. An

incision is then made through the fascia and

periosteum along the linea temporalis posteriorly

to the sinodural angle and then inferiorly on the

mastoid bone to the mastoid tip. The Lempert

periosteal elevator is used to free the postauricular

tissues from the underlying cortex, posterior to

the sinodural angle and forward until the spine of

Henle and the external auditory canal are identi-

ﬁed. Care must be taken not to tear into the

external auditory canal because this would in-

troduce a possible route for infection. If this

should occur, the patient is placed on prophylactic

antibiotics, the defect into the external auditory

canal is repaired, and the operation is continued.

Self-retaining retractors are placed to maintain

the ear forward and to elevate the temporalis

muscle superiorly. Suction on the posterior blade

of the retractor removes excess irrigation ﬂuid and

blood from the wound.

Cortical mastoidectomy

After adequate exposure of the cortex has been

obtained, bone removal is carried out with con-

tinuous suction-irrigation and a large cutting bur.

Bone removal is started along the external audi-

tory canal, and then a horizontal incision is made

along the temporal line. The junction of these

incisions lies over the mastoid antrum. Identiﬁca-

tion of the mastoid antrum and the lateral semi-

circular canal therein is the key to the beginning

dissection of the temporal bone.

Bone removal continues with care taken not to

undercut the mastoid cortex. The external open-

ing must be as large as possible. The middle fossa

plate is identiﬁed superiorly and the sigmoid sinus

posteriorly. Removal of bone is then continued

over the sigmoid sinus to the area of the posterior

fossa dura. In large tumors, bone removal is

carried out far behind the sigmoid sinus. In

some cases, the bone is removed with a rongeur

or drill as far as 2 or 3 cm posterior to the sigmoid

sinus and inferiorly beneath the cerebellar hemi-

sphere. This gives more decompression of the

posterior fossa and allows room for retraction of

the dura posteriorly. Care must be taken, how-

ever, not to injure the dura. Dural tears allow the

cerebellum to herniate into the defect, which may

result in infarction of that portion of the

cerebellum.

Removal of bone over the sigmoid must be

done carefully. If the cutting bur tears the sigmoid

Fig. 2. Skin incision 2 cm behind the postauricular sarcous.

254

BRACKMANN & GREEN

sinus, profuse bleeding ensues and requires pack-

ing with oxidized regenerated cellulose (Surgicel).

Large emissary veins often arise from the poste-

rior aspect of the sigmoid sinus. They can be

identiﬁed through the bone as it is removed, since

suction-irrigation keeps the bone clean. If the

emissary vein is injured, bleeding must be con-

trolled with bone wax, cautery, Surgicel packing,

or in some cases suture of the emissary.

and the ability to identify the structures as they

are encountered. This appreciation of the anat-

omy comes only after many hours of diligent tem-

poral bone dissection.

Labyrinthectomy

After the mastoid air cells have been removed

to the level of the horizontal semicircular canal,

labyrinthectomy is begun. Bone is removed in the

sinodural angle along the superior petrosal sinus.

This area, which is farthest from the facial nerve,

is the key to this step in the dissection. The

opening along the superior petrosal sinus is

gradually deepened and widened until the laby-

rinthine bone is encountered. The lateral and

posterior semicircular canals are then progres-

sively removed, and the facial nerve, which lies

anteriorly, is carefully approached ( Fig. 4 ). The

lateral semicircular canal is opened, and the

common crus of the superior and posterior semi-

circular canals is identiﬁed deep in the dissection.

The superior semicircular canal is followed to its

ampulla. The vestibule is then opened, and the fa-

cial nerve is skeletonized from the genu inferiorly

to near the stylomastoid foramen. It is not neces-

sary to remove bone lateral to the facial nerve;

rather, the facial nerve is skeletonized from a pos-

terior direction, where access is needed to ap-

proach the cerebellopontine angle.

Complete, simple mastoidectomy

As soon as the mastoid cortex has been

removed and the sigmoid sinus has been outlined,

the operating microscope is brought into place.

Magniﬁcation allows more accurate bone removal

and exposure of all the structures of the temporal

bone. A thin layer of bone is left over the sigmoid

sinus and around the emissary veins, and a com-

plete, simple mastoidectomy is performed down to

the level of the horizontal semicircular canal

( Fig. 3 ). It is important that the antrum be opened

and the horizontal semicircular canal be identi-

ﬁed. This canal is the basic landmark in temporal

bone surgery. Once the position of this canal is

known, the depth and three-dimensional relation-

ship of the facial nerve and posterior and superior

semicircular canals can be viewed. Expertise in

temporal bone surgery depends on a thorough

knowledge of the anatomy of the temporal bone

Fig. 3. Mastoidectomy is completed. Facial nerve is localized and sigmoid sinus skeletonized.

TRANSLABYRINTHINE APPROACH FOR ACOUSTIC TUMOR REMOVAL

255

Fig. 4. Semicircular canals are opened. An island of bone over the sigmoid sinus is created.

The ﬁnal removal of bone along the facial

nerve is accomplished with a diamond bur.

Having removed the labyrinthine bone from

posterior to the nerve, the surgeon may then use

the side of the diamond bur rather than the end

and at all times view the plane between the side of

the bur and the facial nerve. This reduces the

hazard of injury to the facial nerve, which is very

slight with this technique. As the facial nerve is

skeletonized, the cribriform area of the superior

vestibular nerve entering the vestibule is seen. It is

important to skeletonize the facial nerve ade-

quately so that the vestibule can be seen in this

area ( Fig. 5 ).

tissue. Dissection is carried inferior to the laby-

rinth, with removal of the retrofacial air cells, un-

til the blueness of the dome of the jugular bulb is

seen through the overlying bone.

As the bone posterior to the internal auditory

canal is removed, the vestibular aqueduct and the

beginning of the endolymphatic sac are removed.

Bone is further removed along the posterior fossa

dura beneath the sigmoid sinus. If the sigmoid

sinus is overhanging into the mastoid cavity,

which makes the dissection di cult, the eggshell

covering of bone over the sinus may be removed

so that the sinus can be retraced posteriorly. It is

good to leave an island of bone (Bill’s island) over

the dome of the sigmoid sinus to protect it from

the rotating bur and retraction of the suction-

irrigation at this point.

We complete the dissection around the in-

ferior portion of the internal auditory canal ﬁrst.

This is the area that is farthest from the facial

nerve, and we ﬁnd that completing the dissection

here makes orientation to the superior portion of

the internal auditory canal easier. Bone removal

is continued medially and anteriorly between the

dome of the jugular bulb and the internal

auditory canal until the cochlear aqueduct is

identiﬁed.

The cochlear aqueduct is not always readily

identiﬁable. In large tumors, it is occluded at its

Internal auditory canal dissection

After the labyrinthine bone has been removed

to the level of the vestibule, dissection of the bone

surrounding the internal auditory canal is started

( Fig. 6 ). This dissection is started along the supe-

rior petrosal sinus and then is gradually enlarged

in all directions toward the internal auditory ca-

nal. The dura of the internal auditory canal is

identiﬁed posteriorly, as is the dura of the poste-

rior fossa. This bone is gently removed, with

care taken to leave an eggshell thickness of bone

over the dura of the internal auditory canal and

the posterior fossa to prevent injury to the soft

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