8/11/2019 bahan CPA

1/13

An acoustic neurinoma is the most common tumor of the cerebellopontine angle.

Advancements in surgery of the cerebellopontine angle are directly reflected in the history of

improvements used in both the diagnosis and treatment of acoustic neurinomas.

Sir Charles Ballance performed the first successful removal of an acoustic neurinoma in

1894. The tumor was approached through a suboccipital craniectomy and was removed byblunt finger enucleation. Cushing subsequently developed a subtotal intracapsular technique,

which markedly decreased the operative mortality. Walter Dandy accomplished the first

complete resection of an acoustic neurinoma in 1917. Dandy, in 1925 described what nowserves as the basis for the current operative approach. He outlined a technique utilizing a

unilateral suboccipital craniectomy with internal decompression of the tumor and stressed the

importance of unroofing the internal auditory meatus for complete resection. Givre and

Olivecrona pioneered preservation of the facial nerve during removal of acoustic tumors.Rand and Kurze reported preservation of the cochlear as well as the facial nerve in 1968.

Developments in microsurgical technique and early diagnosis through computed tomography

(CT) and magnetic resonance imaging have resulted in the detection of smaller tumors thatcan be removed with more reliable preservation of cranial nerve function. The use of

intraoperative auditory evoked potential monitoring to help preserve hearing and the use ofdirect intraoperative seventh cranial nerve stimulation has also played an important role in

the successful resection of acoustic tumors. These advances in diagnostic and surgical

techniques used for the treatment of acoustic neurinomas have also led to a progressively

lower morbidity and mortality for the resection of all cerebellopontine angle lesions.

Clinical Features

The differential diagnosis of cerebellopontine angle lesions includes, in order of occurrence,

acoustic neurinomas, meningiomas, epidermoid tumors and arachnoid cysts. Significantlyless common lesions include neurinomas of other cranial nerves, lipomas, glomus tumors andvascular lesions.

Acoustic neurinomas arise from the Schwann cells of the vestibular nerve. The vestibular

nerve is ensheathed in oligodendrocytes for much of its course through the cerebellopontine

angle. However, as the nerve enters the internal auditory meatus the oligodendrocytes arereplaced by Schwann cells in a region known as the zone of Obersteiner-Redlich. This

transitional zone usually lies at the mouth of the internal auditory meatus and thus Schwann

cells invest the vestibular nerve along virtually all of its length within the canal. It is these

cells within the canal which are thought to give rise to the acoustic neurinoma.

A history of progressive unilateral hearing loss, usually over many months and sometimes

years, is the hallmark of an acoustic neurinoma. In most cases it is associated with tinnitus.As the tumor enlarges, the patient complains of unsteadiness and loss of balance. True

rotational vertigo is rare. The facial nerve usually functions normally until the tumor reaches

a large size. When nerve function is compromised, it is usually mild. Total facial paralysis israre. Involvement of the trigeminal nerve likewise occurs late and is seen primarily in tumors

more than 3 cm in diameter. As the tumor grows upward into the superior aspect of the

8/11/2019 bahan CPA

2/13

cerebellopontine angle, it encroaches upon the trigeminal nerve, producing a gradual

decrease of the corneal reflex and facial analgesia and anesthesia. Tic douloureux occurs

rarely.

It is unusual for patients with an acoustic neurinoma to present with complaints of

swallowing dysfunction or hoarseness and lower cranial nerve involvement is unlikely unlessthe tumor is large. Cerebellar symptoms and signs also occur late in the clinical course of

these tumors and are often found in association with compromised function of cranial nerves.

Papilledema and symptoms of hydrocephalus can also be present and are usually secondaryto compression of the brain stem and the fourth ventricle by a large tumor.

Meningiomas are the second most frequent tumor of the cerebellopontine angle. Theyconstitute 3 to 13 percent of cerebellopontine angle tumors. These tumors produce the same

general symptoms and signs as do acoustic tumors, with several exceptions. Often these

lesions originate from the superior-anterior lip of the porus acousticus, and are associated

with early involvement of the seventh nerve. Hearing loss, however, occurs later. Thus, in

terms of facial and auditory function, meningiomas are the exact opposite of acoustic tumors.Involvement of the posterior root of the fifth cranial nerve may lead to numbness of the face

and ticlike symptoms. These symptoms, preceding hearing loss, suggest that a meningiomamay be present or, less likely, a trigeminal neurinoma. Meningiomas also cause a higher

incidence of lower cranial nerve abnormalities compared to acoustic tumors. The growth

downward of these lesions results in hoarseness, numbness of the throat or complaints of

difficulty swallowing. As with acoustic tumors, large meningiomas can produce cerebellarsymptoms and signs or hydrocephalus with increased intracranial pressure.

Epidermoid tumors and arachnoid cysts are both rare lesions of the cerebellopontine angle,accounting for 2 to 6 percent and 1 to 3 percent of all lesions, respectively. Epidermoid

tumors are benign and grow slowly. They can present with multiple cranial nerveabnormalities or cerebellar symptoms and signs which develop over a number of years.Patients with arachnoid cysts can present with a complaint of unilateral hearing loss,

headache or imbalance. Facial or trigeminal nerve dysfunction can occasionally be observed.

Anatomy

The cerebellopontine angle is an inverted triangular cistern in which the fifth, seventh and

eighth cranial nerves, along with the anterior inferior cerebellar artery (AICA) and the

superior petrosal vein are located. From a surgeon' s viewpoint, the cistern is bounded

laterally by the back wall of the petrous bone, medially by the pons and cephalad by thetentorium. which forms the base of the triangle. This cistern communicates freely with the

other cerebrospinal fluid (CSF) spaces within the posterior fossa, including a small

diverticulum which extends into the porus acusticus.

At the upper aspect of the cistern, the fifth cranial appears as a broad white band, extending

from the lateral aspect of the pons into Meckel's cave. The superior petrosal vein lies at theupper posterior edge of this nerve, and drains from the superior aspect of the cerebellum to

the superior petrosal sinus. This vein is usually 1 to 2 mm in diameter and at times may be

8/11/2019 bahan CPA

3/13

made up of a cluster of veins.

The seventh and eighth nerves course laterally from the pontomedullary junction to theinternal auditory canal. They cross the cistern as an apparent single nerve, which is composed

of four discrete nerves: the superior and inferior vestibular nerves, the cochlear nerve and the

facial nerve. When viewed from the suboccipital approach. the vestibular nerves form theposterior aspect, or the portion closest to the surgeon. The facial nerve makes up the anterior

superior portion within this bundle and the cochlear division of the eighth nerve makes up the

anterior inferior portion. When one looks into the posterior fossa from the extreme lateralaspect of a suboccipital approach, the sixth nerve is occasionally seen, coursing from its

origin at the pontomedullary junction to its entrance into the dura of the clivus (Dorello's

canal). In situations where the tumor has rotated and displaced the brain stem, this nerve may

be confused with the seventh nerve, inasmuch as it exits on the same plane as the seventhnerve and enters the dura at the same level as the internal auditory canal.

The ninth, tenth and eleventh nerves, although not specifically within the cerebellopontine

angle cistern, are found immediately below its inferior margin. The most superior of thesenerves, the ninth, appears round and shiny and is made up of a single filament. The tenth

nerve consists of multiple filaments that are flat, whereas the eleventh nerve is unique inhaving a spinal root traversing the foramen magnum.

The anterior inferior cerebellar artery has a variable location within the cistern. In acoustictumors, this vessel is usually located in the arachnoid over the cleft between the cerebellum

and the dome of the tumor.

Operative Approaches

Suboccipital- Transmeatal Approach

A number of operative approaches to the cerebellopontine angle have been described,including a suboccipital-transmeatal, a translabyrinthine, a middle fossa, a translabyrinthine-

transtentorial and a subtemporal-transtentorial approach. The authors prefer the suboccipital-

transmeatal approach.

Operative Technique

Following the induction of general anaesthesia, the patient is placed on the operating room

table in a lateral position. Some neurosurgeons insert lumbar spinal drain and the distal end

of the tubing is brought out underneath the operating room table for the anaesthesiologist,who controls the CSF drainage during surgery. (In general the drain remains closed until thedura is exposed and the surgeon is ready to open the dura.) The patient is then moved into the

final lateral position with a roll under the lower axilla. The shoulders and hips are taped to

the table to allow manipulation of the table in all planes without risk of the patient slipping. Itis important to place gentle traction on the shoulder of the upper arm parallel to the body to

pull the shoulder out of the operative field. The head is then fixed with a Mayfield clamp

with a moderate degree of flexion and slight rotation to bring the mastoid tip to the top of the

8/11/2019 bahan CPA

4/13

operative field.

Table rotation is used to the advantage of the surgeon during the operation as the line of sightinto the cerebellopontine angle is maximized by moving the patient rather than the surgeon,

who usually sits in one position during the operation. The surgeon's chair is on casters and

has adjustable arm rests adaptable for any surgeon and any patient. The combination ofmoving the chair and the operating room table brings almost all cerebellopontine angle

lesions into a comfortable line of sight for the surgeon.

The skin preparation and draping are routine. Furosemide and mannitol are given prior to

making the skin incision. In the unusual patient who presents with clinically manifested

hydrocephalus, we perform a ventriculoperitoneal shunt 7 to 10 days before the tumorsurgery. The time delay allows the wound to heal and the risk of infection is then minimal. It

is wise to consider placing the shunt on the side opposite the tumor so the tubing does not

encroach on the suboccipital surgical site.

A two-limbed incision that begins 2 to 3 cm below and 1 cm medial to the mastoid tip andwhich extends vertically to the level of the top of the pinna and then curves medially toward

the external occipital protuberance. The medial limb can be shortened or lengtheneddepending on the degree of exposure needed. This incision gives adequate exposure of the

occipital bone and at the time of closure, provides sufficient galea to cover most of the upper

transverse aspect of the wound. It also eliminates the need to transect the suboccipitalmusculature in a nonanatomic plane. The scalp flap can be easily dissected off the occipital

bone with monopolar electrocautery. Caution must be used when opening the inferior portion

of the vertical limb of the incision. medial to the mastoid tip. Rarely an anomalous vertebral

artery can be found coursing up between the muscles and the bone. A variable number ofemissary veins, connecting the external venous system of the scalp with the underlying

sinuses, can be encountered during the dissection. Although they may bleed profusely theyare easily controlled with coagulation and bone wax.

The craniectomy is performed using multiple burr holes followed by bone removal with a

rongeur or drill. The craniectomy should be large enough to expose the sigmoid sinuslaterally and the transverse sinus superiorly. It is not uncommon to encounter large venous

channels during the bony dissection, especially as the sigmoid sinus is approached. Bleeding

from the bone is controlled with bone wax, whereas bleeding from the sinus can becontrolled with a small piece of Gelfoam . Mastoid air cells overlying the sigmoid sinus are

also frequently encountered during the craniectomy. These can serve as a guide as one

approaches the sinus and should be waxed thoroughly before the dura is opened. As the

craniectomy is completed, the spinal drain is opened, if it was inserted.

The dural opening is started in the center of the craniectomy and is opened first in the

direction of the junction of the transverse and sigmoid sinuses. A second incision is madetoward the inferior aspect of the craniectomy, completing a triangle with the sigmoid sinus as

its base. The resulting flap of dura is then reflected back and tacked to the cervical

musculature with nylon suture. The dural opening is completed by making two more radialcuts starting from the apex of the dural triangle. The first cut extends toward the transverse

8/11/2019 bahan CPA

5/13

sinus and the second cut extends toward the inferior medial portion of the craniectomy. The

resulting smaller leaves of dura are tacked back. The object, however, is to completely open

the dura to provide adequate exposure regardless, of the number of dural incisions.

At the time of closure, lyodura is used if the dural leaves do not approximate easily. By the

time the dura is opened, the combination of spinal drainage and gravity has pulled thecerebellum away from the petrous bone. The patient is then rolled toward the surgeon far

enough to position the petrous bone vertically. This manoeuvre, plus slight retraction with a

1-cm blade of a Greenberg retractor, exposes the arachnoid of the cerebellopontine angle.The superior petrosal vein, extending from the cerebellum to the junction of the tentorium

and the petrous bone is coagulated as soon as it is visualized. Traction on this vein. which

can be made up of multiple smaller vessels, can lead to troublesome, although not dangerous

bleeding. An effective way to manage a disrupted vein is to cover it with a small piece ofGelfoam and a cottonoid and after the bleeding has stopped, remove the pack and coagulate

the vessel. Bleeding from these veins looks quite serious in the small confines of the

cerebellopontine angle but is always low-pressure bleeding and can always be managed with

conservative measures.

With slight retraction of the cerebellum at its junction with the tumor, the surgeon can pullthe arachnoid tight and divide it between the surface vessels of the tumor. As the surface

vessels are identified, they are coagulated and dissected carefully along the arachnoid. This

simple manoeuvre of opening the arachnoid establishes the critical tissue planes between the

tumor and the side of the pons, as well as the lower cranial nerves and the AICA. The latter isoften found buried in the arachnoid at the junction of the cerebellum and the dome of the

tumor. Once a clear view of the tumor is achieved, stimulation of the exposed surface in an

attempt to locate the seventh nerve is performed because the relationship of the nerve and thetumor may be variable, especially with meningiomas. With acoustic tumors the course of the

nerve can also be variable, but is usually located anterior to the tumor. After the seventh

nerve leaves the pontomedullary junction, it may course directly toward the internal auditory

canal under the lower pole of the tumor and at other times it may course superiorly along theside of the pons up toward the root entry zone of the trigeminal nerve and follow the course

of this nerve back to the petrous bone . In large tumors, the nerve is often very thin and

difficult to identify, but with stimulation it is possible.

There are several possible techniques applicable to the ultimate removal of the tumor. These

include the laser, the ultrasonic aspirator and bipolar coagulation with concomitant suction.Most neurosurgeons use primarily a bipolar coagulation technique with continuous irrigation

and suction. This allows for a bloodless field. In large tumors, the removal begins in the

center of the surface facing the surgeon. The slow and meticulous removal of the tumor

internally and gradually outward allows the capsule to fall inward. This decompression of thetumor in essence changes a large tumor into a small one and allows the eventual visualization

of the cranial nerves and vessels and permits the surgeon to define their relationship to the

tumor. After the center of the tumor has been decompressed, the dissection is best carried outrostrally in the region of the fifth nerve. This nerve is easily identified and tolerate dissection

better than the lower cranial nerves.

8/11/2019 bahan CPA

6/13

By following this nerve medially to identify the entrance into the brain stem, this is then

followed by exposure of cranial nerves IX, X, and XI, located at the lower pole of the tumor.

As the interface between the pons and the tumor becomes apparent, small pieces of Gelfoamare inserted between the two to give gentle retraction and at the same time protect the side of

the pons and the related vessels. Attempts to pull on the tumor or to manipulate it without

adequate tumor decompression will, under most circumstances, result in serious problems.

Special care must be exercised in the management of the ninth and tenth cranial nerves.

These nerves are extremely sensitive to traction or trauma and must be protected verycarefully. As soon as possible, we free them from the underlying arachnoid and tumor

surface with sharp dissection and cover them with cottonoids.

After the tumor has been reduced in volume to the point at which it is anatomically free of

the fifth, ninth, tenth and eleventh cranial nerves and the lateral aspect of the pons, it

becomes possible to identify the seventh nerve as it exits from the brain stem beneath the

choroid plexus protruding from the foramen of Luschka. This location is ventral and slightly

above the root entry zone of the vestibular nerves. The facial nerve has a distinct. silvery,shiny appearance. In contrast, the vestibular nerves are dull in colour and are somewhat tan.

The removal of smaller cerebellopontine angle lesions is easier because the relationship of

the lesion to most of the important structures can be defined readily. In the removal of small

acoustic tumors and in large acoustic tumors after they have been reduced in size, the internalauditory canal must then be unroofed. By drilling off the roof of the canal back to the fundus,

it is possible to assure a complete removal of the tumor and of equal importance, to expose a

portion of the seventh nerve that is free of tumor. This serves as an excellent starting point

for developing the plane between the seventh nerve and the tumor.

Unroofing of the canal is started by coagulating the dura adherent to the petrous bone. Thebone can be removed with any high-speed drill. The drilling must go far enough to exposethe fundus of the canal and particularly the transverse crest (which is oriented vertically in

the lateral position). When viewed in the lateral position, the transverse crest separates the

superior and inferior vestibular nerves superficially in the canal and the facial and cochlearnerves deep in the canal. In general, the unroofing of the canal is started with a cutting burr:

the surgeon switches to a diamond drill as the outline of the canal becomes apparent. Prior to

drilling, the relationship between the jugular bulb and the canal should be ascertained fromthe CT scan because they may be in close proximity. During the unroofing process, air cells

in the posterior wall of the internal auditory canal may be opened. It is essential that these be

sealed prior to closure. either with bone wax, Gelfoam, muscle, or fibrin glue, for they are a

potential source of postoperative CSF leakage. Following the bony dissection of the canal.the dura of the canal is opened with microscissors. starting at the medial end.

Commonly, there is a 1- to 2-mm area in the fundus that is free of tumor and, by gentlydissecting in this area, the nerves may be exposed and identified. The intracanalicular portion

of the tumor generally has a loose attachment to the seventh nerve, usually at the origin:

subsequent sharp and blunt dissection allows easy separation along their anatomic plane.Once the tumor has been freed from its attachments within the canal it can be dissected back

8/11/2019 bahan CPA

7/13

to the lip of the canal. Care must be exercised by the surgeon at this stage of the operation

because the seventh nerve becomes broad and thin and sometimes takes on the appearance of

thickened arachnoid, especially as it goes over the edge of the lip of the canal. This thinnedout portion is the point where the seventh nerve is most vulnerable.

After removal of the last remnant of tumor, air cells that have been exposed during drillingmust be sealed. The sealing process can be with bone wax applied with a Penfield dissector

and tamped into place with a cottonoid, If a number of air cells are opened or are difficult to

seal with bone wax. a piece of Gelfoam covered with muscle and held in place with fibringlue provides an effective seal. Extra time spent during this phase of the operation is

worthwhile because it minimizes the risk of postoperative CSF leakage.

Prior to dural closure, multiple Valsalva manoeuvres are performed to confirm venous

haemostasis. The subarachnoid space is irrigated until clear. An attempt is always made to

close the dura primarily: however closure with lyodura or thick periosteum harvested nearby,

may be necessary.

In cases where a large tumor has been removed and a potential for cerebellar swelling exists,

the dura is left patulous. It is preferable to monitor postoperative intracranial pressure byway of a subdural catheter. This catheter is tunnelled out from the incision though a separate

stab wound above the horizontal limb of the opening. This catheter may also serve as a CSF

drain.If a small bone flap has been turned during the opening, this can be replaced.Alternatively, if the patient is concerned about cosmesis, a cranioplasty can be performed.

The scalp wound is then closed in a two-layered fashion with 2-0 Vicryl for the galea and 3-0nylon interrupted mattress or subcuticular sutures for the skin. Care must be taken to close

the muscle and fascial layers of the inferior portion of the vertical limb of the incision

because this region may leak CSF if not adequately closed.

Results

Mortality rate is ranging between 1.6 - 5 percent depending upon the patients categories.

Anatomical preservation of the facial nerve is ranging between 60-90 percent depending

upon various factors, such as tumor size. Preservation of sound sensation also rangingbetween 20-66 percent.

Middle Fossa Approach

The middle fossa approach, as described by House in 1961 involves an extraduralsubtemporal approach with microneurosurgical unroofing of the internal auditory canal. Thisapproach is limited to the excision of small intracanalicular tumors that have not escaped the

confines of the internal auditory canal. It is usually performed in patients in whom hearing

remains at a functional level, providing a chance of hearing preservation.

Translabyrinthine Approach

8/11/2019 bahan CPA

8/13

The microsurgical translabyrinthine approach was described by House in 1964. It exposes the

posterior fossa dura in the retromeatal trigone (Trautmann's triangle) formed by the sigmoid

sinus, the jugular bulb and the superior petrosal sinus. This approach is usually reserved forpatients with moderate-size tumors (1.0 to 2.5 cm in diameter). Unfortunately, any

preoperative auditory function is lost as a consequence of this approach.

Translabyrinthine-transtentorial Approach

The combined translabyrinthine-transtentorial approach has been used for the removal oflesions of the cerebellopontine angle. Advantages of this approach, as described by Morrison

and King, include better visualization of the upper pole of the tumor, trigeminal nerve and

brain stem: easier identification of the facial nerve: and minimal cerebellar retraction. Thesurgery is performed through a small lateral scalp flap centered on the ear with a posterior

limb extending down over the mastoid process. This flap is turned to expose the mastoid

process and the upper margin of the external auditory canal. A small bone flap over the

temporal lobe, which exposes the sigmoid sinus, is used. The labyrinthine dissection involves

removal of all of the lateral and superior semicircular canals and most of the posterior canaltogether with the aqueduct of the vestibule and the bone medial and inferior to the vestibule.

The part of the posterior canal that lies most near the descending portion of the facial nerve isleft intact. The bony dissection is continued by exposing the whole length of the sigmoid

sinus down to the jugular bulb and by uncovering the posterior fossa dura, superior petrosal

sinus and middle fossa dura. Finally. the superior, posterior and inferior bony margins of the

internal auditory canal are removed. The dura of the canal can now be opened and the tumorfreed from the facial nerve and dissected from the medial portion of the canal. At this point,

the remaining bone of the floor of the middle fossa overlying the translabyrinthine exposure

is removed. The dura of the temporal lobe and the posterior fossa is then opened and thesuperior petrosal sinus and tentorium are divided. Removal of the remaining tumor resumes,

with the surgeon mobilizing the tumor from the internal auditory canal and freeing the tumor

from the dural margins of the porus. With both medium and large tumors, the arachnoid

covering the tumor is divided completely, with dissection proceeding from the superioraspect. The dissection is completed by internally decompressing and mobilizing the

remaining tumor. Complications described following this approach include dysphasia,

seizures and subdural CSF collections.

Subtemporal-Transtentorial Approach

The subtemporal-transtentorial approach as described by Rosomoff, uses a craniotomy

centered low over the petrous ridge, extending anteriorly over the middle cranial fossa,

superiorly to the parietal boss and posteriorly to a point midway between the mastoid processand the inion. A U-shaped dural flap based on the transverse sinus is made. The temporal

lobe is retracted anteriorly and the occipital lobe is retracted posteriorly. At this point it may

be necessary to divide the vein of Labbe or possibly several smaller veins draining the

temporal and occipital lobes. The petrous ridge and superior petrosal sinus are followed tothe edge of the tentorium, where the trochlear nerve can be identified. The tentorium is

opened close to the petrosal sinus and this opening is angled back to a point behind the

entrance of the trochlear nerve. Retraction of the divided tentorium provides adequate

8/11/2019 bahan CPA

9/13

exposure of the cerebellopontine angle. In the removal of an acoustic tumor, the superior

petrosal sinus is ligated and a dural flap is turned over the acoustic meatus. The roof of the

canal is drilled away and the tumor is dissected free of the nerves. A technique of internaldecompression with mobilization is used to remove the remaining tumor. Complications of

this approach include possible injury to the trochlear nerve, inadequate exposure of the lower

pole of the tumor, postoperative seizures, and temporal lobe dysfunction.

Complications

The two most common complications following surgery of the cerebellopontine angle are

CSF leakage and cranial nerve palsies. Less commonly encountered complications include

bacterial and aseptic meningitis, wound infection, hydrocephalus and haemorrhage.

CSF leakage most often results from a mastoid air cell opened during the craniectomy or

during the drilling of the posterior wall of the internal auditory canal. Fluid then drains fromthese cells into the middle ear and through the eustachian tube down into the pharynx or the

nose. A CSF leak may not present immediately, but may start several days following surgerywhen the patient is mobilized. A small drainage of clear fluid occurring in the immediate

postoperative period may represent fluid that has accumulated in the mastoid air cells at thetime of surgery. A drainage that persists longer than 24 h, or one that worsens with a

Valsalva manoeuvre, is more likely to be a true CSF leak and should be managed

aggressively. This includes placement of a lumbar drain, administration of prophylacticantibiotics, and daily measurement of CSF cell counts. After 5 to 7 days, the drain is

removed and, in usual conditions, the leakage does not recur. If that is unsuccessful, patients

usually undergo a mastoidectomy for obliteration of the air cells and the eustachian tube

without re-exploring of the surgical site.

A CSF leak can also occur from the wound. This is usually a result of poor wound-healing,hydrocephalus, or wound infection. The treatment of the leak actually begins at the time ofthe initial incision. A clean, sharp incision and careful handling of the wound edges is

important. Also, the surgeon must obtain a meticulous closure of the fascial layers, especially

along the inferior aspect of the wound overlying the mastoid tip, where clear fascial planesare not always present. In spite of good technique, a CSF leak may still occur if intracranial

pressure is elevated or if a wound infection develops. In patients with hydrocephalus, simple

stitching of the wound seldom solves the problem unless the hydrocephalus is treatedsimultaneously. If there is no underlying infection, a ventriculoperitoneal shunt is placed. If

the patient has a concurrent infection, a ventriculostomy is placed until the infection has

cleared and a shunt can be inserted.

Dysfunction of cranial nerves V, VII, VIII, IX, X and (rarely) VI can be encountered

following surgery of the cerebellopontine angle. Although cranial nerves IX and X are not by

definition in the cerebellopontine angle, their function can become impaired with theresection of large tumors.

Postoperative facial nerve paresis of various degrees can be evident immediately following

surgery. Interestingly, if there is complete anatomic disruption of the nerve at the time of

8/11/2019 bahan CPA

10/13

surgery, the patient may be able to close the eye for a period of 24 to 48 h following surgery

with a subsequent progression to complete facial paralysis. More commonly, however, the

patient has a variable degree of preserved eye closure and facial movement immediatelypostoperatively. This function also can decline between the third and the fifth postoperative

days, which may be due to oedema or ischemia of the nerve. If the facial nerve paralysis is so

severe that the cornea is inadequately covered, the eye should be covered with a protectiveshield, and artificial tears and a lubricant given every 2 to 4 h. Further therapy depends onwhether the nerve is anatomically intact and whether there is adequate coverage of the

cornea. If the nerve is intact but dysfunctional and the patient has adequate eye closure, the

patient should be followed by recovery of the nerve. If after 12 months the facial nervefunction has not returned, then a facial reanimation procedure can be planned. Various

techniques and results for facial reanimation are discussed in more detail below. Poor lid

coverage of the cornea in more severe cases of facial nerve paresis can be addressed with a

tarsorrhaphy or with the placement of either a spring or weight in the lid. If the facial nerve isdisrupted, facial reanimation is performed early.

Fifth cranial nerve injury can follow removal of a tumor of any size. The fifth nerve functionshould be evaluated immediately postoperatively. If corneal sensation is diminished, the eye

should be covered with a protective shield and artificial tears applied every 2 to 4 h. Ifcorneal sensation is completely absent, the patient is at an increased risk of developing acorneal abrasion, and a tarsorrhaphy should be considered strongly.

Dysphagia with aspiration or hoarseness due to impairment of the glossopharyngeal or vagusnerves can also occur following resection of large tumors in the cerebellopontine angle. If

glossopharyngeal or vagus nerve impairment is suspected, then vocal cord and pharyngeal

sensation and function should be assessed as soon after extubation as possible. A modifiedbarium swallow with video fluoroscopy is often helpful in determining oral pharyngeal

function and the patient's risk of aspiration. If there is evidence of aspiration, NGT or a

feeding gastrostomy tube should be placed until there is adequate recovery of these nerves.

Diplopia can occur after resection of large tumors. It is usually from abducens nerve paresis

and the majority of patients improve spontaneously. Patching the affected eye can give somerelief to the patient until the nerve function returns.

A postoperative fever and/or headache, with or without nuchal rigidity suggests thepossibility of either bacterial or aseptic meningitis. Patients with aseptic meningitis present

with symptoms several weeks after surgery, usually as their steroid dose is being tapered.

Evaluation of these patients should include a CT scan and immediate lumbar puncture with

the CSF analyzed for cell counts, Gram stain and cultures. The glucose levels of the CSF andthe serum should be measured as well. Broad-spectrum intravenous antibiotics with good

gram-positive and gram-negative coverage should be started and the steroid dose increased.

If the cultures are negative after 48 h. the antibiotics can be stopped and the steroids can be

slowly tapered off over several weeks.

Although postoperative epidural, subdural and intracerebellar hematomas are rare, theyrepresent the most serious complications and if not properly diagnosed and treated, may lead

8/11/2019 bahan CPA

11/13

to catastrophe. The diagnosis is usually not difficult in the patient who has awakened from

anaesthesia and then become stuporous or comatose. During the early postoperative period,

monitoring of the intracranial pressure via a subdural posterior fossa monitor may help in theearly detection of a developing hematoma. If the deterioration is slow, there may be time for

a CT scan: however, if the deterioration is rapid, the patient is best taken to the operating

room for re-exploration.

Hydrocephalus can occur in the early postoperative period, especially in patients with a large

tumor and preoperative distortion of the fourth ventricle. The patient may becomesymptomatic from increased intracranial pressure or may develop a full flap at the surgical

site. A CT scan can confirm the diagnosis and the patient can be treated initially with a

ventriculostomy. Most patients recover spontaneously and rarely is a ventriculoperitoneal

shunt required.

Facial Paralysis

Several procedures have been developed to improve facial tone and motor function inpatients with facial nerve paralysis. The choice of the procedure is tailored to the individual

patient. The ideal treatment is intracranial end-to-end anastomosis at the time of the initialsurgery. Unfortunately. most often the nerve has been attenuated or destroyed, making this

impossible. The alternatives then are hypoglossal-facial, spinal accessory-facial or phrenic-

facial nerve anastomosis. In cases of longstanding facial paralysis (more than 2 years) othermethods must be used, which include facial dynamic or static reanimation using muscle

transfers, transposition or neuromuscular pedicle grafts.

Timing of Surgery

The timing of surgery depends on the state of integrity of the facial nerve. If it isanatomically severed and cannot be repaired intracranially. it is better to wait 3 to 4 weeks,

then readmit the patient for hypoglossal-facial nerve anastomosis. If the nerve is

anatomically and physiologically preserved during surgery but is without postoperativefunction, the anastomosis is generally not done for at least a year, because about 90 percent

of the patients seem to have adequate, although delayed functional facial nerve recovery.

Hypoglossal-Facial Nerve Anastomosis

This procedure is performed under general anaesthesia, with the patient supine on theoperating room table and with the head turned to the contralateral side. The ear lobe is

stitched up anteriorly, out of the operative field. A postauricular incision is made from half

an inch above the tip of the mastoid process down in front of the sternocleidomastoid muscle,

for a length of approximately 10 cm. The skin and subcutaneous tissue are opened and thefascia and platysma muscle are then divided in a longitudinal fashion. The

sternocleidomastoid muscle is identified and retracted laterally. Dissection continues

superiorly and medially. The cervical fascia is identified and opened. Then the posterior bellyof the digastric muscle is identified and dissection is carried around it until its anteriomedial

tendinous portion is identified. The hypoglossal nerve is located beneath the posterior belly

8/11/2019 bahan CPA

12/13

of the digastric muscle. It may be identified by following the descending ansa hypoglossi up

until it meets with the hypoglossal nerve.

Attention is turned to the area of the mastoid tip. Using a periosteal elevator, the digastric

muscle is partially separated from the periosteum of the mastoid process. The tip of the

mastoid process is rongeured away, improving visualization of the area of the styloid processand the stylomastoid foramen. Sharp dissection for the exposure of the facial nerve at its exit

from the stylomastoid foramen is done. Occasionally, the surgeon must dissect through the

posterior part of the parotid gland to identify this nerve. Once both the facial and hypoglossalnerves have been identified, the hypoglossal nerve is sectioned sharply at the point where it

begins to branch. The facial nerve is sectioned at the stylomastoid foramen. The proximal

end of the hypoglossal nerve is swung upward and posteriorly, adjacent to the posterior belly

of the digastric muscle to contact the distal end of the facial nerve. Using microsurgicaltechnique, the two ends are anastomosed using 10-0 Prolene sutures. Care must be taken to

ensure that the nerve is not angulated or under tension. After the anastomosis is complete, the

wound is closed in a standard fashion. Another alternative is to section half of the

hypoglossal nerve and perform anastamosing so as not to loose completely the essentialfunction of the hypoglossal nerve.

Spinal Accessory-Facial Nerve Anastomosis

The incision is identical to the one used for the hypoglossal-facial nerve anastomosis. Thesternocleidomastoid muscle is identified and retracted laterally and inferiorly, exposing the

posterior belly of the digastric muscle, The spinal accessory nerve may be identified entering

the posterior aspect of the sternocleidomastoid muscle. To expose the distal end of the facial

nerve, the technique described above is used. Once the facial nerve has been divided at thestylomastoid foramen, the spinal accessory nerve is sectioned in its most distal portion,

roughly where it enters the sternocleidomastoid muscle. The proximal spinal accessory nerveis swung around superiorly and posteriorly and is sutured to the distal facial nerve.

Phrenic-Facial Nerve Anastomosis

Two incisions are used. The first is similar to the one described for the hypoglossal-facial and

the spinal accessory-facial nerve anastomoses; it is used to expose the distal facial nerve rightat the stylomastoid foramen. The second incision is placed approximately two finger breadths

above the clavicle in the supraclavicular fossa. The sternocleidomastoid muscle is retracted

medially and superiorly, exposing the anterior scalene muscle. The phrenic nerve is in front

of the anterior scalene muscle, underneath the fascia. Once the nerve is identified, it is cut atits lowermost end on the anterior scalene muscle. The proximal end of the phrenic nerve is

brought up underneath the sternocleidomastoid muscle and is sutured to the cut end of the

facial nerve. It is recommended that the phrenic nerve be cut and brought up first. to help

udge the length of facial nerve that will be needed to perform the anastomosis withouttension. If there is trouble obtaining the needed length, it is always possible to perform a

mastoidectomy and expose the facial nerve higher up in the temporal bone.

8/11/2019 bahan CPA

13/13

Results of Facial Nerve Anastomotic Procedures

with a successful procedure the facial muscular tone show that with a successful procedurethe facial muscular tone shows signs of recovery at 4 to 6 months, with restoration of a

symmetrical face at rest. Movement of the ipsilateral side usually appears first about the oral

commissure, then progresses to the cheek, lips, and orbits over the ensuing 18 months.

Bilateral Acoustic Tumors

Bilateral acoustic tumors are pathognomonic of central neurofibromatosis. In general, the

goals for surgery are preservation of brain stem function followed by preservation of facialnerve function and hearing. It is not wise to remove both tumors at one operation. In general,

the larger tumor is operated on first. Removal of the tumor is carried out using the technique

outlined above. The patient only returns for surgery on the second side after completely

recovering from the first procedure. This includes wound healing as well as recovery offacial nerve function. In the event of facial nerve paralysis following the first operation, the

second one is delayed until the nerve recovers or a facial reanimation procedure can beperformed. In general, tumor removal should be carried out as soon as the tumors are found

because removal of smaller tumors is associated with better results for hearing preservation.