and Dong-yi Han3
(3)
Department of Otolarygngology Head and Neck Surgery, PLA General Hospital, Beijing, 100853, China
Indications
Facial nerve trunk defect from the facial nerve tumor removal with distal stump available
Contraindications
- 1.
The facial muscle has lost its tension due to atrophy and fibrosis; fibrillation potential disappears in the electromyogram (EMG).
- 2.
Patient unable to undergo surgery.
- 3.
Professional voice users who need flexible tongue movement.
Operative Procedures
Body position: Supine position, affected ear side up.
- 1.
Exposure and resection of the facial nerve lesion – different approaches will be required depending on the location of lesions.
- 2.
A post-auricular incision is performed and is extended inferiorly from the mastoid tip to the level of the superior margin of thyroid cartilage along the anterior border of the sternocleidomastoid muscle, keeping the greater auricular nerve intact.
- 3.
Separate the sternocleidomastoid and parotid, expose the mastoid tip, and then use blunt dissection technique to separate the soft tissue in front of the mastoid tip to find the trunk of facial nerve. Divide and cut the trunk as close to the stylomastoid foramen as possible.
- 4.
The sternocleidomastoid is retracted backwards, to expose the facial vein which will be found at the level of hyoid, and then the vein is ligated. The posterior belly of the digastric muscle is retracted upwards to expose the internal and external carotid arteries and the jugular vein. The hypoglossal nerve passes between the arteries and the vein.
- 5.
Divide the trunk of the hypoglossal nerve and its descending limb. Cut the trunk as far distal as possible.
- 6.
An end-to-end anastomosis of the hypoglossal nerve and facial nerve is performed under the microscope. A 9–0 monofilament suture is used to join the nerve sheaths with 4–6 stitches around the circumference. The proximal end of the hypoglossal nerve trunk is anastomosed to the distal end of the facial nerve. The proximal end of the descending branch of the hypoglossal nerve is anastomosed to the distal end of its trunk.
- 7.
Prior to the anastomosis of the main nerves, a short segment of intact vein is placed over the hypoglossal nerve to later slide over the joined nerves to support the anastomosis and prevent the growth of the granulation tissue into it. The vein must have a greater diameter than the nerves to allow for swelling and avoid compression.
- 8.
The cavity is liberally irrigated, any bleeding is controlled. A drain is inserted, the wound is closed and a dressing is applied.
Special Comments
- 1.
The nerves should not be compressed with forceps or traumatized directly with suction.
- 2.
There are three forms of anastomosis of the hypoglossal nerve and facial nerve: ① the trunk of the hypoglossal nerve is cut, and the proximal end of the hypoglossal nerve trunk is joined with distal end of the facial nerve, and the proximal end of the hypoglossal nerve’s descending limb joined with the distal end of its trunk. This is the commonest procedure; ② the descending limb of the hypoglossal nerve is cut, and its proximal end is joined to the distal end of the facial nerve; ③ 1/3–1/2 of the trunk of the hypoglossal nerve is cut diagonally and joined to the distal end of the facial nerve.
- 3.
There are three methods to locate the facial nerve trunk near the stylomastoid foramen: ① the stylomastoid foramen can be found in front of the site where the posterior belly of the digastric muscle attaches to the mastoid; ② the trunk can be found passing forwards about 1 cm deep to the tympanomastoid suture; ③ the trunk of facial nerve runs along the line passing vertically through the middle point between the mastoid tip and inner edge of tragus cartilage.
- 4.
The hypoglossal nerve is located beneath the common facial vein and posterior belly of digastric muscle and it always runs along the lingual artery. These are the three reliable landmarks for identifying the hypoglossal nerve.
- 5.
It is very important to keep the nerve anastomosis free of any tension for the best nerve regrowth. If necessary, the mastoid tip can be drilled off to expose more of the facial nerve and give adequate length.
- 6.
The hypoglossal and facial nerves should be sectioned in such a way that the cut ends have a similar size for better anastomosis.
- 7.
The nerve sutures should be through the sheath only, and not through nerve bundles to avoid scar formation inside the nerve. If the nerve is too thin, the peripheral connective tissue can be sutured loosely and fibrin glue can be used to support the anastomosis.
Complications
- 1.
Conductive deafness due to the direct injury of the tympanic membrane and/or the ossicular chain.
- 2.
Sensorineural hearing impairment due to direct injury to the inner ear or drill contact with the incus transmitting intense vibration to the inner ear.
- 3.
Vertigo due to injury of the semicircular canals or vestibule.
- 4.
Synkinetic movements of the face where unintentional movement of one group of facial muscles occurs with voluntary movement of another group. This is one of the complications of nerve regeneration but can be reduced with effective physical therapy.
- 5.
Facial spasm due to the re-innervation of facial muscle. It may vary from mild flickering of the eyelid to severe spasm and is often permanent.
- 6.
Crocodile tears syndrome due to the lacrimal gland (normally innervated by the greater superficial petrosal nerve) being reinnervated by the salivary gland secretomotor nerve.
- 7.
Permanent facial paralysis due to irreversible nerve degeneration. This may require other facial reanimation or suspension techniques.
- 8.
Unilateral atrophy of tongue due to sacrifice of the hypoglossal nerve.
- 9.
Dysmasesia (Chewing difficulty) and dysphagia in a small number of patients and can be successfully treated with rehabilitation training.
Fig. 5.1
Post-auricular incision, elevate the tympano- meatal flaps forward and expose the tumor
A C-shaped incision, 0.5 cm behind the post-auricular sulcus is performed; skin and subcutaneous tissue are separated to expose the cortex of the mastoid, root of zygoma and posterior and inferior walls of the external auditory canal. The bone of the external auditory canal is eroded, and its inner part is occupied by a tumor whose envelope is intact
Fig. 5.2
Exposure of the antrum and mastoid cavity
Remove the cortex and cells of the mastoid and expose the tympanic sinus and mastoid cavity. The front of the mastoid cavity has been damaged by tumor. After being separated, the tumor is found to penetrate the back wall of external auditory canal and reach the back margin of the parotid
Fig. 5.3
Remove the posterior wall of the external auditory canal, and expose the back margin of tumor
Using an electronic drill, the superior, inferior and posterior margins of the tumor are exposed. The tumor is large and occupies the inner part of external auditory canal and erodes into the mastoid
Fig. 5.4
Remove the bone of the inferior wall of external auditory canal and the mastoid tip
Remove the bone of the inferior wall of external auditory canal and the mastoid tip to identify the lower part of the tumor which has reached the parotid through the stylomastoid foramen
Fig. 5.5
Exposure of the inferior margin of tumor
Remove the bone near the stylomastoid foramen, and expose the inferior margin of the tumor, which is found to originate from the facial nerve. The normal facial nerve is identified just outside the stylomastoid foramen
Fig. 5.6
Cut the distal end facial nerve trunk beyond the tumor
As the facial nerve cannot be preserved, the distal trunk is severed well beyond its junction with the tumor. The end is marked with thread
Fig. 5.7
Expose the superior margin of the tumor
Separate the soft tissue along the tumor, and expose its superior margin. The junction of the tumour and normal facial nerve is located between the horizontal and pyramidal segments
Fig. 5.8
Excise the affected proximal facial nerve and tumor
Cut the facial nerve, a little proximal to its junction with the tumor. The severed end of the horizontal segment should be diathermied or ligated unless nerve transplanting is performed. After removal of the inferior wall of external auditory canal, there is a large cavity, but the tympanic membrane and ossicles can be left intact
Fig. 5.9
Extend the incision, separate the trunk of hypoglossal nerve
Extend the incision inferiorly along the anterior margin of sternocleidomastoid muscle, expose and ligate the facial vein. Retract the sternocleidomastoid and posterior belly of digastric muscles, beneath which there is the hypoglossal nerve passing forwards and downwards near the lingual artery
Fig. 5.10
Anastomosis of hypoglossal nerve and facial nerve
Separate the trunk of the hypoglossal nerve and its descending limb. Cut the trunk as far distal as possible. The proximal end of hypoglossal nerve trunk is anastomosed to the distal end of facial nerve under the microscope. A 9–0 monofilament suture is used to join the nerve sheaths using 4–6 stitches. A segment of intact vein is placed over the proximal hypoglossal nerve before the anastomosis
Fig. 5.11
Covering the nerve anastomosis with a segment of intact vein
After suturing, the anastomosis is surrounded with a segment of intact vein with intact wall. The aditus ad antrum and the floor of the external auditory canal are covered with a temporalis musculofascial flap. Suture the post-auricular incision in layers. Pack the mastoid cavity with gelatin sponge and iodoform gauze, and apply a dressing
CPA Microvascular Decompression (MVD) of Facial Nerve by Retrosigmoid Approach
Wei-dong Shen4 and Dong-yi Han4
(4)
Department of Otolarygngology Head and Neck Surgery, PLA General Hospital, Beijing, 100853, China
Indications
Microvascular decompression (MVD) via a retrosigmoid approach is used to elevate a compressing vascular loop from the affected facial nerve in hemifacial spasm (HFS) and Convulsive Tic Syndrome when medical control is ineffective, or the patients prepared to undergo early surgery. A primary lesion in the CPA must be excluded in all cases, such as facial muscle spasm secondary to trauma, Bell’s palsy and, in rare cases, otitis media with effusion.
Contraindications
Patients unable to tolerate general anesthesia or craniotomy due to poor general health.
Operative Procedures
Microvascular decompression surgery is performed via a Retrosigmoid Approach.
- 1.
Anesthesia and position: All MVD operations are performed under endotracheal general anesthesia. The patient is positioned supine. The head is rotated away from the side of operation.
- 2.
Surgical incision: An anteriorly based U-shaped incision is made over the retroauricular and suboccipital region.
- 3.
Posterior fossa craniotomy: A posterior fossa craniotomy of 4–5 cm diameter is completed in the angle between the posterior border of the sigmoid sinus and the inferior border of the transverse sinus.
- 4.
Exposure to the cerebellopontine angle (CPA): After the bone flap is removed, the dura is incised in a curvilinear, cruciform or T-shaped fashion. Once CSF is drained from the cerebellomedullary cistern, the cerebellum should begin to retract and fall away from the petrous bone and tentorium.
- 4.1.
The most important vascular structure within the CPA is the anterior inferior cerebellar artery (AICA). It arises most commonly as a single trunk from the basilar artery. It courses posteriorly, ventromedial to the facial and vestibulocochlear nerve and takes a long loop laterally to the porus acousticus. In 15–20 % of cases, the AICA actually passes into the lumen of the internal auditory canal before turning back to the brainstem. The AICA can thus be divided into the premeatal, meatal, and postmeatal segments in its course. The main branch of the AICA passes over cranial nerves VII and VIII in only 10 % of cases. The remainder of the cases, it either passes below the VII and VIII cranial nerves or, in 25–50 % of individuals, actually passes between them. Three branches that regularly arise from the meatal segment of the AICA can be identified. Small perforating arteries supply blood to the brainstem. The subarcuate artery passes through the subarcuate fossa into the posterior surface of the temporal bone, and the third regular branch is the internal auditory artery (labyrinthine artery). Cranial nerves VII and VIII receive their blood supply from small braches of AICA.
- 4.2.
The petrosal vein (Dandy vein) drains large parts of the anterior portion of the cerebellar hemisphere and sizeable anterolateral areas of the pons and medulla oblongata to the superior or inferior petrosal sinus. It is closely related to the internal acoustic meatus and may be encountered in the area of the trigeminal nerve anterior to the porus acousticus. Obstruction of the petrosal vein can lead to bleeding, or venous infarction and cerebellar edema.
- 4.3.
The vestibulocochlear nerve root arises from the brainstem at the lateral end of the pontomedullary sulcus, immediately in front of the foramen of Luschka and the lateral recess of the fourth ventricle. The facial nerve arises in the pontomedullary sulcus 1–2 mm anterior to the point at which the vestibulocochlear nerve joins the brainstem. The vestibulocochlear and facial nerves are in close approximation at the porus. The facial nerve enters the facial canal at the anterior-superior quadrant of the lateral end of the meatus.
- 4.4.
As it leaves the brainstem, the facial nerve fibers are sheathed in oligodendroglia derived from the central nervous system. The nerve loses this covering within a few millimeters lateral to the brainstem and becomes ensheathed instead by Schwann cells. The vestibulocochlear nerve sheath is derived from oligodendroglia and extends further lateral than that of the facial nerve (about 15 mm). The junction of the oligodendroglia and Schwann cells (i.e., the Obersteiner-Redlich zone) occurs just medial to the porus acousticus. Most acoustics neuromas arise from Schwann cells in this region.
- 4.5.
The trigeminal nerve root is located superior (approx. 8 mm) to the acoustic-facial bundle and passes through the anterior superior part of CPA to reach the trigeminal ganglion on the petrous apex. The abducens nerve is located in the medial part of the CPA. It leaves the brainstem anterior-inferiorly to the facial nerve and courses along the brainstem in an anterior direction. The lower cranial nerves (the glossopharyngeal, vagus and accessory nerves) are located inferiorly to the acoustic-facial bundle. The upper rootlets of the glossopharyngeal make contact with the vestibulocochlear nerve bundle.
- 4.1.
- 5.
Microvascular decompression: It is most important for a successful microvascular decompression to accuratelyidentify the compressing artery (offending vessel). The nerve-vessel contact area is generally located at the root exit zone (REZ) of the facial nerve in nearly all cases. This zone needs to be systematically inspected for nerve compression; paying particular attention to the PICA compression of the facial nerve inferiorly. The offending vessel may not always be seen in contact with the facial nerve as retraction of several millimeters may have occurred after the dura matter incision and drainage of CSF. A depression on the surface of the facial nerve may be a sign of nerve compression. Careful separation of the vessels, including small veins and arteries, and adherent arachnoid membrane is carried out to free the facial nerve. After identification and separation of the offending vessel, small pieces of temporalis muscle, or Teflon sponge are placed between the vessel and the REZ to prevent any further contacts.
- 6.
Closing technique: Once hemostasis is assured, the operative field is filled with saline using a bulb syringe. Closure is performed with a running suture to the dura and the bone flap is fixed with titanium fixing rivets. The skin sutured in two layers over a subcutaneous drain.
Special Comments
- 1.
Intraoperative monitoring of facial nerve function and of hearing with ABR improve the safety of the CPA Microvascular Decompression.
- 2.
Correct preoperative positioning of the patient greatly assists this procedure. A block is placed under the shoulder and neck is minimally stretched with mild flexion and rotation toward the unaffected side. The table should be rotated laterally. Excess tension on the neck is avoided. The head is secured in a Mayfield headrest system.
- 3.
To reduce the bleeding from the wound, the incision site is injected with a mixture of 2 % lidocaine with l:l000 epinephrine and scalp clips are applied to its edges during the operation.
- 4.
At the beginning of the bony exposure, intravenous mannitol (1.0 g/kg body weight) is administrated to achieve a rapid diuresis and brain relaxation.
- 5.
A craniotomy (4–5 cm in diameter) is required in the posterior fossa.
- 6.
Dural vessels are avoided or sealed with bipolar coagulation before making the incision.
- 7.
The dural incision should be kept 0.5 cm away from the venous sinuses. Care is taken to avoid damage to the transverse and sigmoid sinus and cerebellum when incising the dura.
- 8.
The dura is retracted with 5–0 silk thread to improve exposure.
- 9.
Formal opening of the cisterna magna and drainage of cerebrospinal fluid (CSF) allows for gentle cerebellarretraction and exposure of the CPA. Excessive cerebellar retraction can result in postoperative edema and should be avoided.
- 10.
At the end of the procedure, the dura is closed in a watertight manner. Muscle with fibrin glue is carefully interposed between the interrupted sutures and any open air cells are packed with bone wax, to avoid CSF leakage.
- 11.
After surgery the patient should stay in the intensive care unit (ICU) overnight for close observation.
Complications
- 1.
Hearing loss
- 2.
Intracranial hemorrhage
- 3.
Postoperative brain edema
- 4.
Facial weakness or Facial palsy
- 5.
Cerebrospinal fluid otorrhea
- 6.
Meningitis
- 7.
Post-operative dizziness or headache
Note: It has been reported that there is an 80–85 % effective rate with MVD for HFS. The reported complications related to MVD are low, with partial or complete loss of hearing as the most common. Other complications, such as brainstem infarction or CSF leak are rare. In a retrospective study of 782 MDV for hemifacial spasm, Barker et al. reported complications after the first microvascular decompression for hemifacial spasm included hearing loss in 2.6 % cases and irreversible severe facial weakness in 0.9 % of patients at the operating side. In all 782 microvascular decompression procedures for hemifacial spasm in 703 patients (705 sides, 57 patients underwent more than one procedures), one operative death (0.1 %) and two brainstem infarctions (0.3 %) occurred. The same author also noted that complications were more frequent in reoperated patients.
Fig. 5.12
Posterior Fossa Craniotomy
A U-shaped incision is made over retroauricular and suboccipital region. The bone flap is approximately 4 cm in diameter. The bony opening is placed behind the sigmoid sinus and inferior to the transverse sinus
Fig. 5.13
Incision of Dura Mater
A curvilinear incision is made in the dura and the anterior flap, based on the sigmoid sinus, is tacked forwards. Cottonoids are placed along the incision edges of dura matter to protect the cerebellum
Fig. 5.14
Exposure of the structures in left cerebellopontine angle
Open the arachnoid of the cerebellomedullary cistern to allow drainage of the cerebrospinal fluid and obtain a relaxed cerebellum. At this point, cranial nerves VII and VIII are visualized. Cranial nerve V is also in view in the superior part of the field
Fig. 5.15
Identify and separate offending vessels from the facial nerve
Free up the facial nerve which is located inferior and deep to the auditory nerve using an elevator or hook
Fig. 5.16
Separate the AICA and the acoustico-facial bundle
Separate the AICA and the acoustico-facial bundle using a block of gelatin sponge
Retrosigmoid Sinus Approach for Removal of Acoustic Neuroma
Yi-hui Zou5 and Vincent C Cousins6
(5)
Department of Otolarygngology Head and Neck Surgery, PLA General Hospital, Beijing, 100853, China
(6)
Department of Ear Nose and Throat Surgery, Alfred Hospital, Melbourne, Australia
Indications
- 1.
Tumors located mainly in cerebellopontine angle area.
- 2.
To preserve hearing and facial nerve function when it may be difficult to remove the tumor completely through middle cranial fossa or via a translabyrinthine approach.
Contraindications
- 1.
Small acoustic neuroma located in the internal auditory canal without useable hearing
- 2.
Infection in the area of the operation, such as a scalp furuncle or intracranial infection.
- 3.
The patient’s general health is too poor for surgery to be performed. Chronic infectious diseases such as hepatitis and tuberculosis should be cured or stable before the operation to be performed.
- 4.
Bleeding and clotting disorders. Long term aspirin usage and active menstruation are conditions that may interfere with surgery by causing excessive bleeding or lead to intracranial hemorrhage.
- 5.
In older patients, it may be better not to operate. Tumors such as acoustic neuromas are benign and patients can live for long time with tumors which may not show further growth. The effects of age may add risk to the surgery. Large tumors with brainstem compression will usually require surgery. Careful consideration needs to be given to the relative risks and benefits of this surgery.
Operative Procedures
- 1.
Anaesthesia: This surgery is always performed under general anaesthesia with appropriate monitoring.
- 2.
Incision. A C-shaped post-auricular incision is made from the upper attachment of the auricle to the mastoid, passing 4–5 cm posterior to the sulcus and extending 1–2 cm below the tip on the mastoid process. The flap is elevated anteriorly to expose the skull.
- 3.
Opening the bone window. The upper boundary is the temporal line. The anterior limit is a line joining the parietal notch and the tip of mastoid (the surface projection of the sigmoid sinus). A bone window of about 3 × 4 cm is made in the area where parietal, temporal and occipital bones have a common boundary. The posterior fossa dura is exposed.
- 4.
Incise the dura. An anteriorly based rectangular dural flap is made just inside the margins of the bone window. The upper and anterior boundaries are the temporal line and sigmoid sinus respectively. The flap is reflected forward and held with stay sutures to expose the cerebellum.
- 5.
Exposure of the cerebellopontine angle. The cerebellar surface is protected with moist cottonoids and gently retracted posteriorly with a brain spatula. CSF is aspirated to expose the tumor and the posterior fossa structures. From superior to inferior the cranial nerves are the trigeminal, the facial and acoustic nerve bundle, and the IX (glossopharyngeal), X (vagus) and XI (accessory) nerves inferiorly. The vestibulo-cochlear nerve lies behind the facial nerve at the brainstem. More laterally the upper and lower vestibular nerves lie behind the facial and cochlear nerves respectively.
The abducent nerve (VI) lies well anterior to the acoustico-facial bundle. The hypoglossal nerve is usually not seen in this approach, but lies well anterior and inferior to the IX, X and XI nerves
- 6.
Removal of the tumor. Big acoustic neuromas have a pseudo capsule which can be opened posteriorly and tumor can be gradually removed from within. Once the tumor has been debulked, the capsule can be reflected off the facial and cochlear nerves and complete removal achieved. For small tumors, the involved nerve can be separated from the facial and cochlear nerves and resected directly. Real-time monitoring of facial nerve and hearing (brainstem evoked potential) is used in all cases to assist with their preservation. Acoustic neuromas usually originate from one of the vestibular nerves but always have some attachment to the facial and cochlear nerves and must be clearly separated from them before resection.
- 7.
Opening internal auditory canal. The posterior wall of the internal auditory canal has to be drilled away to expose tumor extending into the canal to remove it completely.
- 8.
Hemostasis. Hemostasis is achieved with use of bipolar electrocoagulation or application of hemostatic gauze. The latter is better for bleeding on the brain surface.
- 9.
Closure of the operative cavity. Suture the dura closed. Reinsert the bone flap and fix it with craniotomy rivets. Suture the scalp in layers and apply a compression dressing.
Special Comments
- 1.
Minimal retraction is used on the cerebellum and brainstem to prevent brain edema and brain herniation. Intracranial pressure can be controlled at the start of the procedure using an agent such as 20 % mannitol. 250 ml is given by rapid intravenous injection.
- 2.
Avoid injury to the main blood vessels and dural venous sinuses. The mastoid emissary and petrosal veins, the anterior inferior cerebellar artery and the sigmoid and transverse sinuses can all cause significant bleeding. Complete hemostasis must be achieved before closing the operative cavity to prevent post-operative intracranial hematoma
- 3.
Protect the facial and cochlear nerves using intra-operative monitoring.
- 4.
Prevent leakage of cerebrospinal fluid. Repair the dura in a watertight fashion. Maintain normal intracranial pressure post-operatively to avoid leakage of cerebrospinal fluid.
Complications
- 1.
Intracranial hemorrhage and hematoma. As mentioned above.
- 2.
Injury of the cerebellum and brainstem, brain edema. Excessive retraction and injury to the cerebellum and brainstem during operation can cause brain edema and permanent neural dysfunction.
- 3.
Injury of facial and acoustic nerves. The nerves are easily damaged when separating and resecting the tumor, leading to facial paralysis, hearing loss and tinnitus. Injury to the facial nerve may necessitate further surgery for repair and partial restoration of function.
- 4.
Damage of the other cranial nerves. Cranial nerves V, IX, X, XI can be damaged with permanent loss of function. Cranial nerves VI and XII are generally not involved as they are located deeply.
- 5.
Leakage of cerebrospinal fluid. Leakage of cerebrospinal fluid can occur when the dural repair is inadequate or postoperative intracranial pressure increases. A compression dressing will help stop a leak of fluid via the wound. Intracranial pressure should be maintained at normal levels.
- 6.
Intracranial infection and meningitis. A strict sterile operation technique and antibiotic administration during and after operation will mostly prevent infection.
- 7.
Brain hernia. Intracranial hemorrhage, hematoma, excessive brain edema and increased intracranial pressure can cause brain herniation. This is likely to be life-threatening and must be recognized early and appropriate action taken.
Surgery 1: Retro-Sigmoid sinus approach for removal of acoustic neuroma
Fig. 5.17
Craniotomy
An anteriorly based C-shaped post-auricular flap is raised with a size of about 5 × 4 cm, to expose the cranial bone and open a bone window. The upper boundary is the temporal line, and the anterior limit is a line between the parietal notch and the tip of the mastoid process. A bone flap of approximately 3 × 4 cm bone is removed from the area where parietal, temporal and occipital bone share a common boundary, behind the sigmoid sinus
Fig. 5.18
Expose tumor in the cerebellopontine angle
A U-shaped dural flap is raised. It is based anteriorly behind the sigmoid sinus and below the transverse sinus. The flap is reflected forwards to expose the cerebellum. The cerebellum is protected with moist cottonoids and gently retracted posteriorly with a brain spatula to expose the tumor in the cerebellopontine angle
Fig. 5.19
Removal of the tumor
First ensure that the facial nerve is not lying on the posterior surface of the tumor using the nerve monitor probe. If not, coagulate the tumor surface, open the capsule and remove the tumor from inside the capsule preserving the facial and cochlear nerves located outside the tumor capsule
Fig. 5.20
Removal of the tumor
Open the posterior wall of the internal auditory canal to expose its contents. Isolate the tumor and remove it completely. The vestibular nerves and tumor are usually posterior to the facial nerve
Fig. 5.21
Separate and protect the facial nerve
Elevate the superficial involved nerves and tumor, to identify the facial nerve more anterior and deep. Separate and resect the tumor progressively under facial nerve monitoring
Fig. 5.22
Protect facial nerve and remove the remaining tumor
Separate and resect tumor progressively under facial nerve monitoring. The remaining tumor can be seen and separated from the intact facial nerve which is seen deeper. The tumor in the internal auditory canal has been removed completely
Fig. 5.23
Preserve the facial and cochlear nerves
Showing the preserved facial and cochlear nerve after the tumor was removed completely
Fig. 5.24
Closure of the operative cavity
Reposition the dural flap after complete hemostasis is assured and suture it with a continuous nylon thread in a watertight fashion
Surgery 2: Retro-Sigmoid sinus approach for removal of acoustic neuroma
Fig. 5.25
Craniotomy
Make an anteriorly based C-shaped post-auricular flap to expose the cranial bone and create a bone window about 3 × 4 cm with its upper boundary at the temporal line, and the anterior limit is a line between the parietal notch and the tip of the mastoid process. Drill holes with a trephine at the four angles or drill along the four borders with a milling cutter or electric drill. Take care not to damage the dura. Any bleeding from the emissary vein or sigmoid sinus should be controlled completely
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